JP2002232298A - Method and device for compressing and restoring data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate data compressing/restoring processing by enabling high speed code registering by applying spray encoding in place of the block calculation of arithmetic codes and registering novel data in a code tree in such spray encoding. SOLUTION: A code tree independent for each context is held and when the combination of input data and the context is not held in a context tree, a code is outputted according to a branch from the apex of the code tree to a leaf, where such input data or specified code is registered (step Q4). Then, the leaf, where such input data or specified code is registered, is exchanged with the other leaf or code defined as a branching point except for the apex (step Q5), the leaf of the code tree, where the specified code is registered, is branched (step Q6) and the specified code and novel data are registered in provided two novel leaves (step Q7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data compression method and a data decompression method, a data compression device and a data decompression device. In recent years, various types of data such as character codes, vector information, and images have been handled by computers, and the amount of data handled has rapidly increased. Along with this, when dealing with large amounts of data, compressing the amount of data by eliminating redundant parts in the data,
Reduction of storage capacity and faster transmission have been performed. Also, universal encoding has been proposed as a method capable of compressing various data by one method.

[0002] The field of the present invention is not limited to character code compression but can be applied to various types of data. In the following, one word unit of data is referred to as a character, following the name used in information theory. In this case, data in which arbitrary words are connected to each other is called a character string.

[0003]

2. Description of the Related Art A method of compressing text data, files, and the like includes a dictionary type coding method using similarity of data series and a statistical coding type method using a frequency of appearance of a data sequence. There is. Among them, a typical technique of probability statistical coding is the above-described universal coding.

Further, there is an encoding called an arithmetic encoding. This arithmetic coding is to generate a code adapted to the appearance probability of each character while calculating without having a code table, and when the appearance frequency of the character of the information source is known, the maximum This method is said to be able to compress efficiently.
There are value arithmetic coding and multi-valued arithmetic coding of three or more values.

Hereinafter, a method of multi-level arithmetic coding will be described. In multi-level arithmetic coding, first, 0 ≦ P <1 (hereinafter, referred to as
The number line of [0, 1) is divided by the number of appearing character events (hereinafter, referred to as symbols). here,
The width of each section is set so as to be proportional to the ratio of the symbol appearance frequencies, and the sections are arranged in descending order of appearance frequency.

[0006] Then, a section corresponding to the appearing symbol is selected, and in the next symbol, the selected section is further divided into sections corresponding to the total number of symbols, and the corresponding symbol section is selected. Subdivided sections. FIG. 70A and FIG. 70B show the processing described above.
This will be specifically described with reference to the drawings for explaining the principle of multi-level arithmetic coding shown in FIG.

FIG. 70A shows an example of a symbol and an appearance frequency, and FIG. 70B shows an example of symbol segmentation. The description will be given taking a case where the section of the character string “ab” is divided as an example. First, a number line [0, 1) is drawn using characters a, a as shown in FIG.
It is divided into five sections b, c, d, and e.

Then, the section [0, 0.2) of the symbol “a” that first appears is selected, and the selected section [0, 0.2] is selected.
0.2) is further divided into five sections of all symbols a to e. Next, a section [0.04, 0.06) of the symbol “b” that appears second is selected, and this section [0.0
, 0.06) is further divided into five sections of all symbols a to e. Thus, by selecting the section of the symbol “e” that appears third, the character string “abe” is selected.
Is obtained [0.05, 0.06).

As described above, by repeating the above-described processing for all the input data, the section of the character string to be encoded can be determined, and any point in the finally determined section of the character string can be determined. Is expressed in binary notation and output as a compression code. The name "arithmetic encoding"
This is because the code word is represented by a binary number below the decimal point, such as [0.11011...], And is calculated.

In the method of dividing a section according to the appearance frequency as described above, a static coding method (static) that divides a section according to a preset appearance frequency without depending on the actual appearance frequency of a character string. , A semi-adaptive coding scheme (s) that divides a section with the appearance frequency obtained by scanning all character strings first.
emi-adaptive), or an adaptive coding method (ada) that recalculates the frequency each time a character appears and resets the section for each character.
ptive).

A method of compressing data in units of bytes (characters) using the above-described multi-level arithmetic coding for file compression is described in, for example, the following two documents. "Arithmetic Coding for Data Compression," Commu
n. of ACM, Vol.30, No.6 PP.520-540 (1986) "An Adaptive Dependency Source Model for Data Co
mpression Scheme, "Commun. of ACM, Vol.32 No.1 PP.
Here, the document discloses a specific algorithm of multi-level arithmetic coding. Also, the multi-level arithmetic coding in this document is one of the methods called entropy coding, which encodes and compresses one character at a time. Is updated successively each time the character appears, and is dynamically adapted to various data for encoding. In addition, in this multi-level arithmetic coding, processing as shown in the flowchart of FIG. 71A is performed in detail.

On the other hand, the method of the literature provides a method of obtaining a high compression rate by expressing a target character by a conditional probability using the immediately preceding character, and encoding the conditional probability by multi-value arithmetic coding. Are sequentially updated, and encoding is performed by dynamically adapting to various data. Also in this multi-level arithmetic coding, processing as shown in the flowchart of FIG. 71 (b) is performed.

Here, instead of multi-level arithmetic coding, dynamic Huffman coding (“Variation a Theme by Huffman”, IEEE Trans. Info
rm.Theory, Vol.24, No.6 1978, or "Design and
Analysis of Dynamic Huffman Codes ", Journal of AC
M, Vol. 34, No. 4 1987) is also conceivable, but dynamic Huffman coding is inferior to multi-valued arithmetic coding in coding efficiency and takes more time to process. No dynamic Huffman coding of probabilities is used in practice.

FIG. 72 is a diagram showing an example of the algorithm of the multi-level arithmetic coding / decoding. In addition, there is a method called a splay (Splay-Tree) encoding method other than the arithmetic encoding (for example, the document “Application of Spla”).
y Tree to Data Compression "by DOUGLAS W.JONES Commu
n.of ACM, Vol31 No.8 P996-1007).

In this spray coding method, FIG.
A symbol is registered at the end of the code tree (generally called a leaf or leaf) using a tree-structured code table (hereinafter referred to as a code tree) as shown in FIG. The distance from a root or a root) to a leaf storing input data is output as a codeword.

More specifically, a code word is assigned "1" when branching to the right when descending from the root to the leaf, and "0" when branching to the left. That is,
In the example of FIG. 73A, the symbol of the symbol A is [1011
0], and the code of the symbol B is [001]. When the code length is changed (the code is updated), it is performed by rearranging the coded leaf with another leaf or a contact point (called a node or a node) on the code tree.

FIG. 73 (b) shows an example of the above-mentioned code update. As shown in FIG. 73 (b), in the input data, the codes of the symbols A, B, C and D are initially stored in the leaves of the code tree. Then, first, the node of the symbol A and the symbol C are rearranged, and further, the node of the upper node D of the symbol A and the node of the symbol E are rearranged. As a result, as shown in FIG. ] To [110], and the code is updated.

Here, the above description is about the case where the appearance probability of each character is dynamically variable-length coded. To further increase the compression ratio, the dependency between the input signal and the immediately preceding character is determined. This is performed by dynamically variable-length encoding the conditional appearance probability incorporating. This method is a stochastic coding using a stochastic property of data. As shown in FIG. 74, a context collection process 511 and a dynamic variable length coding process 5 are performed.
12 is a two-step process.

Then, as shown in FIG. 75 (a), the context of the context of the character string is collected from the input data by context collection, and a tree structure of the context as shown in FIG. 75 (b) is created. Dynamic variable length coding is performed to find the attached probability. Here, the above-mentioned conditional probability is obtained by counting the number of appearances each time a character string passing through the character of each node appears on a context tree having a tree structure as shown in FIG. 75 (b). Can be

By the way, there are mainly the following two methods of context collection for obtaining conditional probabilities. Hereinafter, the number of characters of a condition (context) is referred to as an order (see "Data Compression Using Adaptive Coding and Part").
ial String Matching "JOHN G.CLEARY and others IEEE Vol.COM
-32, No. 4 APRIL 1984 P396-402). (1) Context collection method of fixed order This method is a method of setting the condition of the conditional probability to a fixed number of characters.

For example, in a secondary context, the contexts of the characters connected to the two immediately preceding characters are collected, and the conditional probability p (y | x1,
x2) is encoded. Here, y is the coded character of interest, x
1 and x2 are the immediately preceding first and second characters, respectively. (2) Blending context collection method In the above-described fixed-order context collection method, when the immediately preceding conditional string is difficult to appear, the estimation of the conditional probability becomes inaccurate,
Conversely, when the immediately preceding conditional character string is likely to appear, the estimation of the conditional probability becomes accurate, leaving the possibility that the degree can be further increased.

In general, a higher compression ratio can be obtained for data having a higher correlation between characters as a higher-order context is used. On the contrary, a compression ratio is reduced for data having a lower correlation as a higher-order context is used. become worse. The solution to this is the context Bl
ending (mixing of orders). This method is a method of extending the order of the context by adapting it to the input data in such a manner that the order is raised when the order is easy to output without fixing the previous order, and the order is low when the output is difficult.

[0023]

However, the stochastic coding method using arithmetic coding as a dynamic variable length code has the problem that every time data is input, the accumulated data is accumulated. Since the frequency is recalculated and the number line of [0, 1) is re-divided, a complicated and large amount of arithmetic processing is required, and there is a problem that the processing cannot be speeded up.

The present invention has been made in view of the above problems, and applies spray coding instead of arithmetic code interval calculation, and registers new data in a code tree in this spray coding. High-speed code registration processing has been enabled to speed up data compression / decompression processing.
An object of the present invention is to provide a data compression method and a data decompression method, and a data compression device and a data decompression device.

[0025]

Therefore, a data compression method according to the present invention employs the following steps in a data compression method for encoding and compressing input data according to a history that has appeared in the past. It is a feature (claim 1). (1) A context tree holding step of holding a context tree in which a combination of input data and a context consisting of n pieces of continuous data is registered. (2) A code tree holding process for holding an independent code tree for each context. (3) A new context tree registration process for newly registering data in the context tree of the context tree holding process when the combination of the input data and the context is not held in the context tree holding process. (4) A code for storing data in a new leaf obtained by branching a leaf as a data storage point of a code tree in a code tree holding process when a combination of input data and a context is not held in the context tree holding process Tree new registration process. (5) A context changing step of changing the context when the combination of the input data and the context is not held in the context tree holding step. (6) A code output step of outputting a code according to a branch from a vertex of a code tree to a leaf in which input data or a specific code in the code tree is registered. (7) A code length changing step of replacing a leaf in which input data or a specific code in a code tree is registered with a node defined as a branch point other than the top of another leaf or the code tree. (8) In the code tree new registration step, a leaf in which a specific code is registered is branched, and a specific code and new data are registered in the obtained two new leaves.

The data compression method according to the present invention is characterized in that the following steps are taken in a data compression method for encoding and compressing input data according to a history that has appeared in the past. ). (1) A code tree holding step of holding a code tree in which an escape code defined in advance as data indicating non-registration is registered. (2) A context tree holding step of holding a context tree in which a combination of input data and a context consisting of n consecutive data is registered. (3) A new context tree registration process for newly registering data in the context tree of the context tree holding process when a combination of the input data and the context is not held in the context tree holding process. (4) A code for storing data in a new leaf obtained by branching a leaf as a data storage point of a code tree in a code tree holding process when a combination of input data and a context is not held in the context tree holding process Tree new registration process. (5) A context changing step of changing the context when the combination of the input data and the context is not held in the context tree holding step. (6) A code output process of outputting a code in accordance with a branch from the top of the code tree to a leaf in which input data or an escape code is registered. (7) A code length changing step of replacing a leaf in which input data or an escape code is registered with another leaf or a node defined as a branch point other than the vertex of the code tree. (8) In the code tree new registration step, a leaf in which an escape code is registered is branched, and an escape code and new data are registered in the obtained two new leaves.

Further, the above-described code tree new registration process (4)
Divides the leaf with the longest distance from the root defined as the vertex of the code tree among the leaves under the same context, and obtains two new leaves and the data stored in the diverged leaf. The new data may be registered (claim 3), and among the leaves under the same context, the last registered leaf is branched and stored in the obtained two new leaves in the branched leaf. The registered data and new data may be registered (claim 4).

On the other hand, the data restoration method of the present invention is characterized in that the following steps are taken in a data restoration method for decoding a code obtained by encoding input data in accordance with the history of past input data ( Claim 5). (1) A context tree holding step of holding a context tree in which a combination of decrypted data and a context is registered. (2) A code tree holding process for holding independent code trees according to contexts. (3) A code tree determining step of determining a code tree of a code from data decoded immediately before. (4) A decoding process in which the code is decoded by scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code. (5) A context changing step of changing the context when the reached leaf is a specific code in the code tree. (6) A code length changing process of recombining the leaf of the decoded data and the specific code with another leaf or a node as a branch point. (7) A new registration step of newly registering the decoded data in the code tree when the specific code is decoded. (8) A context tree registration process of registering the data registered in the new registration process in the context tree of the context tree holding process. (9) In the new registration step, the same leaf as the branch selected on the encoding side is branched and new data is registered.

Further, the data restoration method of the present invention is characterized in that the following steps are taken in a data restoration method for decoding a code obtained by encoding input data according to the history of past input data ( Claim 6). (1) A code tree holding step of holding a code tree in which an escape code defined in advance as data indicating data not registered is stored. (2) A context tree holding step of holding a context tree in which a combination of the decrypted data and the context is registered. (3) A code tree determining step of determining a code tree of a code from data decoded immediately before. (4) A decoding process in which the code is decoded by scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code. (5) A context change process for changing the context when the reached leaf is an escape code. (6) A code length changing step of recombining the leaf of the decoded data and the escape code with another leaf or a node as a branch point. (7) A new registration step of newly registering the decoded data in the code tree when the escape code is decoded. (8) A context tree registration process of registering the data registered in the new registration process in the context tree of the context tree holding process. (9) In the new registration step, the same leaf as the branch selected on the encoding side is branched and new data is registered.

FIG. 9 is a block diagram showing the principle of an apparatus for implementing the data compression method according to the present invention. The data compression apparatus shown in FIG. 9 encodes input data according to a history that has appeared in the past. Here, 301 is a code tree holding unit, 302 is a context tree holding unit, 303 is a context registration unit, 304 is a code registration unit, 305 is a context change unit, 306 is an encoding unit,
Reference numeral 07 denotes a code updating unit.

The code tree holding means 301 holds a code tree in which an escape code defined in advance as data indicating data not registered is registered.
Numeral 02 holds a context tree in which a combination of input data and a context is registered. The context registration unit 303 encodes an escape code and newly registers data in the context tree.

Further, the code registering means 304 encodes the escape code, branches the leaf as the data storage point of the escape code in the code tree, and newly registers the data. When the combination of the input data and the context is not stored in the context tree, the context is changed. Also, the encoding means 30
Reference numeral 6 denotes a code that outputs a code according to a branch from the top of the code tree to input data or a leaf in which an escape code is registered, and the code updating unit 307 registers the encoded data and the escape code. A leaf is replaced with another leaf or node (claim 7).

FIG. 10 is a block diagram showing the principle of the apparatus for implementing the data compression method according to the present invention. The data compression apparatus shown in FIG. 10 also encodes input data according to a history that has appeared in the past. The data compression apparatus shown in FIG. 10 has the same code tree holding means 301, context tree holding means 302, context registration means 303, and context change means 3 as those in FIG.
05, encoding means 306, and code updating means 307, and a description thereof will be omitted.

Reference numeral 310 denotes a branch position search means.
The branch position search means 310 searches for a leaf having the longest code length on a code tree. Reference numeral 311 denotes a code registration unit. The code registration unit 311 encodes an escape code, branches a leaf as a data storage point searched by the branch position search unit 110, and newly registers data. There is (the above, claim 8).

FIG. 11 is a block diagram showing the principle of the apparatus for implementing the data compression method according to the present invention. The data compression device shown in FIG. 11 also encodes input data according to a history that has appeared in the past. Here, in the data compression apparatus shown in FIG. 11, the same code tree holding means 301, context tree holding means 302, context registration means 303, context change means 305, coding means 306, A sign updating unit 307 is provided, and a description thereof will be omitted.

Reference numeral 308 denotes a branch position holding unit. The branch position holding unit 308 holds a leaf position as a data storage point newly registered in the code tree. Further, reference numeral 309 denotes a code registration unit. After the code registration unit 309 encodes the escape code,
The leaf at the position held by the branch position holding means 308 is branched and data is newly registered (claim 9).

On the other hand, the configuration of an apparatus for implementing the data restoration method of the present invention according to claim 4 is shown in the principle block diagram of FIG. The data restoration device shown in FIG.
It decodes a code obtained by encoding input data according to the history of past input data. Here, 401 is a code tree holding unit, 402 is a context tree holding unit, 403 is a code tree determining unit, 404 is a decoding unit, 405 is a context changing unit,
Reference numeral 06 denotes a code updating unit, 407 denotes a code registration unit, and 408 denotes a context tree registration unit.

The code tree holding means 401 holds a code tree in which an escape code defined in advance as data indicating that data has not been registered is registered.
2 stores a context tree in which a combination of the decoded data and the context is registered.
Determines the code tree of the code from the data decoded immediately before.

Further, the decoding means 404 decodes the code by scanning from the root meaning the vertex of the code tree to the leaf as the data storage point in accordance with the code. If it is an escape code, the context is changed, and the code updating means 406 recombines the decoded data and the escape code leaf with another leaf or a node as a branch point.

The code registration means 407 branches the escape code leaf and newly registers the decoded data when the escape code is decoded. The registered data is registered in the context tree of the context holding unit 402 (the claim 10).

FIG. 13 is a block diagram showing the principle of the configuration of an apparatus for implementing the data restoration method according to the present invention. The data restoration apparatus shown in FIG. 13 also decodes a code obtained by encoding input data according to the history of past input data. Here, the data restoration apparatus shown in FIG. Code tree holding means 401, context tree holding means 402, code tree determining means 403, decoding means 404, context changing means 40 similar to those shown.
5, a sign updating means 406 is provided, and the description thereof is omitted.

Reference numeral 411 denotes branch position searching means.
The branch position search means 411 searches for the position of the leaf having the longest code length in the code tree. And
Reference numeral 412 denotes a code registration unit.
Is to encode the escape code and then branch the leaf searched by the branch position search means 411 to newly register data.

Reference numeral 413 denotes a context tree registration unit.
This context tree registration means 413 registers the data registered by the code registration means 412 in the context tree of the context tree holding means 402 (claim 11). Further, claim 6
FIG. 14 is a block diagram showing the principle of the apparatus for implementing the data restoration method of the present invention described in FIG. This FIG.
Also decodes a code obtained by encoding input data according to the history of past input data.

Here, in the data restoration apparatus shown in FIG. 14, the same code tree holding means 401, context tree holding means 402, code tree determining means 403, decoding means 404, and context tree as those shown in FIG. A change unit 405 and a sign update unit 406 are provided, and a description thereof will be omitted. Reference numeral 409 denotes a branch position holding unit. The branch position holding unit 409 holds a position of a leaf newly registered in the code tree.

Reference numeral 410 denotes a code registration unit. The code registration unit 410 encodes an escape code, branches a leaf at a position held in the branch position holding unit 409, and newly stores data. It is to register. Reference numeral 414 denotes a context tree registration unit. The context tree registration unit 414 registers the data registered by the code registration unit 410 in the context tree of the context holding unit 402 (the claim 12). The data compression method of the present invention has the following operation (claim 1). (1) By the context tree holding process, it is possible to hold a context tree in which a combination of input data and a context consisting of n pieces of continuous data is registered. (2) By a code tree holding process, an independent code tree can be held for each context. (3) By the context tree new registration process, when the combination of the input data and the context is not held in the context tree holding process, data can be newly registered in the context tree of the context tree holding process. (4) When a combination of input data and context is not held in the context tree holding process by the code tree new registration process, a new leaf obtained by branching a leaf as a code tree data storage point in the code tree holding process. Data can be stored on leaves. (5) By the context change process, the context can be changed when the combination of the input data and the context is not held in the context tree holding process. (6) By the code output process, a code can be output according to the input data from the vertex of the code tree or the branch to the leaf where the specific code in the code tree is registered. (7) By the code length changing process, the leaf in which the input data or the specific code in the code tree is registered can be replaced with another leaf or a node defined as a branch point other than the vertex of the code tree. (8) In the code tree new registration process, a leaf in which a specific code is registered can be branched, and a specific code and new data can be registered in the obtained two new leaves.

Further, the data compression method of the present invention has the following operation (claim 2). (1) By the code tree holding process, a code tree in which an escape code defined in advance as data indicating unregistered data can be stored. (2) By the context tree holding process, it is possible to hold a context tree in which a combination of input data and a context consisting of n pieces of continuous data is registered. (3) By the context tree new registration process, when the combination of the input data and the context is not held in the context tree holding process, data can be newly registered in the context tree of the context tree holding process. (4) When a combination of input data and context is not held in the context tree holding process by the code tree new registration process, a new leaf obtained by branching a leaf as a code tree data storage point in the code tree holding process. Data can be stored on leaves. (5) By the context change process, the context can be changed when the combination of the input data and the context is not held in the context tree holding process. (6) Through the code output process, a code can be output according to the input data from the top of the code tree or the branch to the leaf where the escape code is registered. (7) By the code length changing process, the leaf in which the input data or the escape code is registered can be replaced with another leaf or a node defined as a branch point other than the vertex of the code tree. (8) In the code tree new registration process, a leaf in which an escape code is registered can be branched, and an escape code and new data can be registered in the obtained two new leaves.

Also, in the above-described code tree new registration process of (4), among the leaves under the same context, the leaf having the longest distance from the root defined as the vertex of the code tree is branched and obtained. The data stored in the branched leaf and the new data can also be registered in the two new leaves (claim 3). Of the leaves under the same context, the last registered leaf is branched. The data stored in the branched leaf and the new data can be registered in the obtained two new leaves (claim 4).

On the other hand, the data restoration method of the present invention has the following operation (claim 5). (1) The context tree in which the combination of the decrypted data and the context is registered can be held by the context tree holding process. (2) By the code tree holding process, each independent code tree can be held according to the context. (3) The code tree of the code can be determined from the data decoded immediately before by the code tree determination process. (4) Through the decoding process, the code can be decoded by scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code. (5) If the reached leaf is a specific code in the code tree by the context change process, the context can be changed. (6) Through the code length changing process, the leaf of the decoded data and the specific code can be combined with another leaf or a node as a branch point. (7) By the new registration process, when the specific code is decoded, the decoded data can be newly registered in the code tree. (8) By the context tree registration process, data registered in the new registration process can be registered in the context tree in the context tree holding process. (9) In the new registration process, the same leaf as the branch selected on the encoding side can be branched to register new data.

Further, the data restoration method of the present invention has the following operation (claim 6). (1) By the code tree holding process, a code tree in which an escape code defined in advance as data indicating that data has not been registered can be held. (2) By the context tree holding process, a context tree in which a combination of the decrypted data and the context is registered can be held. (3) The code tree of the code can be determined from the data decoded immediately before by the code tree determination process. (4) Through the decoding process, the code can be decoded by scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code. (5) If the reached leaf is an escape code in the context change process, the context can be changed. (6) Through the code length changing process, the leaf of the decoded data and the escape code can be recombined with another leaf or a node as a branch point. (7) By the new registration process, when the escape code is decoded, the decoded data can be newly registered in the code tree. (8) By the context tree registration process, data registered in the new registration process can be registered in the context tree in the context tree holding process. (9) In the new registration process, the same leaf as the branch selected on the encoding side can be branched to register new data.

Also, having the configuration described with reference to FIG.
In an apparatus for performing the data compression method of the present invention, that is, a data compression apparatus that encodes input data according to a history that has appeared in the past, the code tree holding unit 301 includes:
A code tree in which an escape code defined as data indicating unregistered data is registered in advance, and a context tree holding unit 302 stores a context tree in which a combination of input data and a context is registered.

After the context registering means 303 encodes the escape code, the data is newly registered in the context tree, and the code registering means 304 encodes the escape code and stores the escape code data of the code tree. The leaf as a point is branched and data is newly registered, and the context change unit 305 changes the context when the combination of the input data and the context is not held in the context tree.

Further, the encoding means 306 outputs a code according to a branch from the top of the code tree to the input data or the leaf where the escape code is registered, and the code updating means 307 outputs the encoded data and the escape code. Replaces a registered leaf with another leaf or node (claim 7). Further, in an apparatus for implementing the data compression method of the present invention having the configuration described with reference to FIG. 10, that is, a data compression apparatus that encodes input data according to a history that has appeared in the past,
The code tree holding unit 301 holds a code tree in which an escape code defined in advance as data indicating that data is not registered is registered, and the context tree holding unit 302 holds a context tree in which a combination of input data and a context is registered. I do.

Then, after the context registration means 303 encodes the escape code, newly registers data in the context tree, and the branch position search means 310 searches for a leaf having the longest code length on the code tree. , The code registration means 311 encodes the escape code, and then the branch position search means 3
Then, a leaf as a data storage point searched at 10 is branched and data is newly registered.

Further, the context changing means 305 changes the context when the combination of the input data and the context is not held in the context tree, and the coding means 306 registers the input data or the escape code from the top of the code tree. The code is output in accordance with the branch to the leaf that has been set, and the code updating unit 307 replaces the leaf in which the encoded data and the escape code are registered with another leaf or node (the above-described claim 8).

An apparatus having the configuration described with reference to FIG. 11 for implementing the data compression method of the present invention, that is, a data compression apparatus that encodes input data in accordance with the history of past occurrences, Code tree holding means 301
Holds a code tree in which an escape code defined in advance as data indicating unregistered data is registered, and a context tree holding unit 302 holds a context tree in which a combination of input data and a context is registered.

After the context registering means 303 encodes the escape code, the data is newly registered in the context tree, and the branch position holding means 308 stores the position of the leaf as the data storage point newly registered in the code tree. After the code registration unit 309 encodes the escape code, the leaf at the position held by the branch position holding unit 308 is branched and data is newly registered.

Further, the context changing means 305 changes the context when the combination of the input data and the context is not held in the context tree, and the coding means 306 registers the input data or the escape code from the top of the code tree. A code is output according to a branch to a certain leaf, and the code updating means 30
7 replaces the leaf in which the encoded data and the escape code are registered with another leaf or a node as a branch point (claim 9).

On the other hand, an apparatus for implementing the data restoration method of the present invention having the configuration described with reference to FIG. 12, that is, data for decoding a code obtained by encoding input data according to the history of past input data. In the restoration apparatus, the code tree holding unit 401 holds a code tree in which an escape code defined in advance as data indicating data not registered is registered, and the context holding unit 402 registers a combination of the decoded data and the context. The tree is held, and the code tree determining unit 403 determines the code tree of the code from the data decoded up to immediately before.

Then, the decoding means 404 decodes the code by scanning from the root meaning the vertex of the code tree to the leaf as the data storage point in accordance with the code, and decodes the code.
If the leaf reached is an escape code, change the context. Further, the code updating unit 406 recombines the decoded data and the escape code leaf with another leaf or a node as a branch point. When the code registration unit 407 decodes the escape code, the escape code leaf is branched and decoded. The registered data is newly registered, and the context tree registration unit 408 registers the data registered by the code registration unit 407 in the context tree of the context holding unit 402 (claim 10).

Further, an apparatus for implementing the described data restoration method of the present invention having the configuration described with reference to FIG. 13, that is, decoding a code obtained by encoding input data in accordance with the history of past input data. In the data restoration apparatus, the code tree holding unit 401 holds a code tree in which an escape code defined in advance as data indicating that data is not registered is registered, and the context holding unit 402 registers a combination of the decoded data and the context. The code tree determining means 403 determines the code tree of the code from the data decoded up to immediately before.

The decoding means 404 decodes the code by scanning from the root meaning the vertex of the code tree to the leaf as the data storage point in accordance with the code, and decodes the code.
But if the leaf reached is an escape code,
Change context. Further, the leaf of the data and the escape code decoded by the code updating unit 406 are recombined with another leaf or a node as a branch point, and the branch position searching unit 411 searches for the position of the leaf having the longest code length in the code tree, The code registration unit 412 encodes the escape code, branches the leaf searched by the branch position search unit 411, and newly registers data. The context tree registration unit 408 stores the data registered by the code registration unit 412 in the context. Register in the context tree of the holding means 402
1).

An apparatus for implementing the data restoration method of the present invention having the configuration described with reference to FIG. 14, that is, data for decoding a code obtained by encoding input data in accordance with the history of past input data. In the decompression device, the code tree holding unit 401 holds a code tree in which an escape code defined in advance as data indicating data not registered is registered, and the context holding unit 402 registers a combination of the decoded data and the context. The context tree is retained, and the code tree determining unit 403 determines the code tree of the code from the data decoded up to immediately before.

Then, the decoding means 404 decodes the code by scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code, and decodes the code.
5, when the reached leaf is an escape code, the context is changed, the data decoded by the code updating means 406 and the leaf of the escape code are rearranged with another leaf or a node as a branch point, and the branch position holding means 4 is changed.
09 holds the position of the leaf newly registered in the code tree.

Further, after the code registration unit 410 encodes the escape code, the leaf at the position held in the branch position holding unit 409 is branched to newly register data, and the context tree registration unit 408 codes the escape code. Registration means 410
Is registered in the context tree of the context holding means 402 (claim 12).

[0065]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (a) Description of Technology 1 Related to the Present Invention FIG. 15 is a block diagram showing a configuration example of a data compression device and a data decompression device as technology 1 related to the present invention.
In FIG. 15, reference numeral 1 denotes a data compression device that encodes and compresses input characters according to a history of past appearances, and 2 denotes a data restoration device that restores characters encoded by the data compression device 1. is there.

Further, the data compression device 1 collects the context of the input character string data to create a context tree, and handles the context (context tree) obtained in the context collection process 11. Then, a spray encoding step 12 is performed in which a code tree corresponding to the spray code is created and updated while spray encoding according to the character string of the input data. On the other hand, the data decompression device 2 creates / generates a code tree in which a spray code is made to correspond to the context of the decompression data encoded by the data compression device 1 while performing spray coding in accordance with the character string of the decompression data. A splay encoding process 21 for updating, and a context collection process 22 for collecting context (creating a context tree) for a character string as restored data
To take.

In the following, the data compression apparatus 1 is described as an encoding side, and the data decompression apparatus 2 is described as a decompression side. (1) Description on the Encoding Side FIGS. 16A and 16B are diagrams showing an example of a context tree created in the context collection process 11, and FIG. FIG. 16B shows an example in which a character string is stored in a memory in a list-structured storage format so that the character string can be searched in a short time. FIG. 16B shows a tree-structured dictionary (list) storing character strings by connecting parent-child relationships. FIG.

Here, the address in FIG.
In the example of FIG. 16A, the maximum size of the context tree is 4K nodes (4KW). in this way,
If all characters are registered in advance, the first route that leads to the route
Since the positions of the sibling nodes in the hierarchy are known in advance, there is no need to manipulate the list at the time of the search, and direct access can be made.

On the other hand, in the second and subsequent hierarchies, the addresses of the child node and the right sibling node are stored, and the list is manipulated and accessed until the characters are matched while matching the stored characters in a list format during search. When the context tree is initialized, up to the address 100 is set. At this time, an End Of File (EOF) code is registered in the address 100 of the first hierarchy, and the memory after the address 101 is stored. Used for new registration.

Next, FIG. 17 is a diagram showing an example of a code tree created in the above-described splay encoding step 12. The code tree is basically set as shown in FIG. 17 at the time of initialization, similarly to the conventional Splay-Tree coding. Then, corresponding to FIG. 16B, the maximum size is 4K nodes (4K nodes).
In the case up to W), the tree nodes of the code are classified into two nodes: an internal node (with a child node) and an external node (the end of each code without a leaf or child node).

In the splay coding, the Up, Lef as shown in FIG.
Three sequences, t and Right, are used. Where U
The p array stores the address from each node to the parent node, the Left array stores the address from each node to the left child node, and the Right array stores the address from each node to the right child node. Is what you do.

In the Up array, the internal nodes are set to the first 4
KW (address (hexadecimal) 000 to FFF),
Set the external node to the remaining 4KW (address (hexadecimal) 1000
-1FFF). By doing so, the code for each node of the context tree is represented by the code tree address = context tree node pointer (number) + 4K,
Can be associated with each other.

The bit width of each array is 1 for the Up array.
3 bits, Left and Right arrays are 12 bits. Next, a basic operation of updating the tree of the code tree having the above-described configuration will be described with reference to FIGS. FIG. 19A is a diagram showing a basic operation of updating the spray code. As shown in FIG.
Is accessed, the node A and the branch with the node A two stages above and the branch C in the opposite direction are exchanged.

Then, for the characters A to E,
When the character C is accessed, for example, as shown in FIG.
As shown in (1), the code tree is rearranged. In other words, the tree of the code tree is updated by repeating the above-described basic operation twice. In this case, the second basic operation updates the length of the parent node of the first updated node.

As a result, even if the depth of the code tree is increased, the basic operation is repeated to reduce the length from the root to the accessed node C (reference numeral 0110) to （(reference numeral 10). Therefore, the code table from the root to the accessed node can be dynamically rearranged to adapt the code table to the input data. That is, the sign update of the spray code is performed by Move-
It is like performing a To-Front operation on a Binary-Tree.

Further, the process of creating the context tree in the context collection process 11 and the process of updating and creating the code tree in the spray encoding process 12 will be described in detail with reference to the processing steps E1 to E31 in the flowchart of FIG. Will be described. The input character is K (K is an arbitrary character), and the character input immediately before the character K is input is P (P is an arbitrary character).

First, the context tree, the code tree, and the preceding character P are initialized (step E1). Then, it is checked whether or not all the characters already input have been input-encoded (step E2). If any input characters remain, the input of the character K and the setting of the length L of the character string to 0 are performed. Perform (Step E3). Further, it is checked whether there is a child node under the character P immediately before the context tree (step E5). If there is no child node under the character P immediately before, the 0th order code of the input character K is output (step E6). Then, the input character K is registered as a child node under the character P immediately before the context tree (step E7).

On the other hand, in the code tree, a node for registering the character K and the escape code is created below the immediately preceding character P, and the character K is registered (step E8). 30A and 30B show an example of this node creation algorithm.
Shown in Further, the immediately preceding character is changed to the input character K (step E16), and the length L 'of the immediately preceding character string is changed to the maximum character string length L.
It is checked whether it is equal to max (step E24).

If the preceding character string length L 'is not equal to the maximum character string length Lmax, it is checked whether the preceding character string is encoded and output by the primary code (step E).
25). Here, if the preceding character string is not encoded by the primary code, the target character string length L is shifted to the preceding character string length L '(step E28), and it is checked whether the character K has been encoded (step E9). If the encoding has been completed, the processing from step E2 is repeated (YES route of step E9), and if the encoding has not been completed, the processing from step E3 is repeated (NO route of step E9).

If the character registered in the child node matches the input character K in step E10, the length L of the character string is increased by 1 (step E1).
7), the character string length L is the maximum code length Lm set in advance.
It is checked whether it is equal to ax (step E18). If they are not equal, it is checked whether all the characters of the input data have been encoded (step E19). If there is any character that has not been encoded yet, the input character so far is moved to the immediately preceding character P (step E20), Further, one character K is input (step E21), and the process returns to the above-described step E10, where it is again checked whether the character registered in the child node matches the character K.

If they do not match, it is checked whether the length L of the character string is 0 (step E11).
That is, if there is a child node below the preceding character P, but the corresponding character K has not yet been attached, the escape code under the preceding character P is output, and then the zero-order code of the character K is output (step E12). ). Further, the character K is registered as a sibling node of a child node under the character P immediately before the context tree (step E13), and the escape code under the character P immediately before the code tree is divided into an escape code and a code of the character K. Then, the code of the character K is added (step E14), and the escape code of the code tree and the code length of the zero-order code K are updated as the spray code (step E15).

As described above, it is possible to register the decompressed character string of the encoded character string until a predetermined maximum character string length is reached. Then, step E described above
16. After step E24, it is checked again whether the immediately preceding character string has been output with the primary code (step E25). That is, if the immediately preceding character string is encoded by the primary code and output, the extended character string obtained by adding the leading character of the encoded character (string) to the immediately preceding character string is registered in the context tree (step E26).
The code of the encoded extended character string is registered in the code tree (step E27), and the processing from step E28 described above is repeated.

This registration is performed such that the code of the immediately preceding character is branched and the primary code of the character string to which the character K is added is added. The branching of the character string is performed by considering the escape code as the code of the character string obtained by encoding the character string and forming the original character string and the code of the character string to which the character K is added. In this way,
As a dictionary registration character string, the character string is registered from the encoded immediately preceding character, and the character string following the immediately preceding character is encoded.

Further, in the above-mentioned step E18,
When the character string length L is equal to the preset maximum code length Lmax, or in step E11, the character string length L
Is not equal to 0, the primary code corresponding to the reference number of the character (string) of the context tree is output (step E22), and the code length of the primary code output by the code tree is updated as the spray code (step E22). E23), and then the above step E24
The processing from is performed.

Here, when the combination of the preceding character P and the input character K has already been registered in the context tree, the closed loop processing expands the number of registered characters (character string length), and The process of performing registration is shown. Also, in step E2, if all the input characters have been encoded, it is checked whether there is a child node under the character P immediately before the context tree (step E29). The escape code below the character P is output (from the NO route of step E29 to step E30), and En
The 0th-order code of the EOF representing d Of File is output (step E31), and the process is terminated (step E31 from the NO route of step E29).

If there is no child node, EOF 0
The next code is output, and the process ends. In the data compression method that encodes and compresses a character string as input data according to the history that appeared in the past by performing the above processing, the character string of the input data is collected in a dictionary, registered with a number At the same time, the splay code is encoded and updated corresponding to each character string.

Here, the above-mentioned input character K is limited to any one of the alphabets a, b and c, and the characters "abc abc
Taking the case where "ab b" is input as an example, the update and creation of the context tree and the code tree will be described in further detail with reference to FIGS. First, as shown in FIGS. 21 (a) and 21 (b), characters a, b, and c and a terminal code EOF that is output after encoding all input data are previously written in a context tree and a code tree.
Are registered as _{a 1, b 2, c 3} , EOF 4 by referring to numbers.

By initializing the context tree in this way, any of the characters a, b, and c registered first becomes the immediately preceding character, and when there is no context following the immediately preceding character, an independent single reference number is also used. Will also serve. In the following description, the character c
Is assumed to be the first preceding character. On the other hand, FIG.
As shown in the figure, when the node descends from the root to the lower left, the code “0” is added to the registered character.
Is a binary tree that assigns the code “1” to the registered character when the node goes down to the lower right, so that at the time of encoding, the path from the node of the reference number of the corresponding character to the root is stacked. Then, by reversing the path and allocating the codes “0” and “1” according to whether it is the lower left or the lower right, the code word corresponding to the reference number of the character can be obtained.

That is, the zero-order code of the three characters “a ₁ , b ₂ , c ₃ ” is “00 0110 11”. Then, the above-described FIG. 21 (a), the from the state shown in (b), when the first character string "abc" is entered, so assuming a previously registered "c" (c ₃₎ the immediately preceding character As shown in FIG. 22A, a new node is created below the context tree “c” (c ₃ ), and the first character “a ₅ ” of the character string “abc” is unregistered. And an escape code (ESC ₆ ) representing the same.

On the other hand, in the code tree, as shown in FIG. 22B, since "a" has already been registered, the node in which "a" is registered and the upper-order character of "c" which is the immediately preceding character The node is rearranged, this “c” is newly set as a root (primary encoding), and “a” and an escape code (ESC)
Register Further, in the character string "abc", the next b,
By performing the above-described processing for c, the context tree and the code tree when b is input are respectively shown in FIG.
(A) and (b), and the context tree and code tree when c is input are as shown in FIGS. 24 (a) and (b).

This processing is the same as the processing steps described above with reference to FIG.
This corresponds to a closed loop process via the YES route of No. 24 and the NO route of Step E25. That is,
In the context tree, when no child node exists below the immediately preceding character, a new node for registering the input character and the escape code is created and registered below the immediately preceding character.

On the other hand, in the code tree, when the same character as the previously registered character is input again, the node of the previously registered character is registered as the character immediately before the input character. By replacing the node with the upper node of the node, the node of the character registered in the past is moved to the upper level, the distance from the root is reduced to half, and the code length is shortened.

[0093] In addition, followed and by the character string "abc" is input, the lower of the "c _9" in the context tree as just before character last of the "c" of the first input string "abc", character Although only one character “a” in the column “abc” is to be registered, “a ₅ ” is already registered under “c ₃ ” in the context tree, as shown in FIG. FIG. 25
As shown in (a), the character to be registered is expanded by one character from one character “a” to two characters “ab”, and “b” is added below “a ₅ ”.
₁₁ Register.

At this time, in the code tree, as shown in FIG. 25 (b), a node of an escape code (ESC) registered together with "a" below "c" is branched and a new node is created. Then, "a" registered by expanding one character in the context tree
b ”is registered. Then, in the character string "abc",
When “b” is to be registered in the context tree, FIG.
As shown in FIG. 26A, since “b ₇ ” is already registered below “a ₁ ”, as shown in FIG. 26A, the character to be registered is changed from one character “b” to two characters “b 1”. One character is expanded to “bc” and “c ₁₂ ” is registered below “b ₇ ”.

At this time, in the code tree, as shown in FIG. 26 (b), the node of the escape code (ESC) registered with "b" below "a" is branched and a new node is created. Then, "b" registered by extending one character in the context tree
c "is registered. Also, when the last "c" of the next character string "abc" is registered, the above processing is performed to obtain the context tree and the code tree as shown in FIG.
The state shown in (b) is reached (the “abc ab
c "is already input).

When the character string "ab" is further input, the context tree first attempts to register one character "a" below the immediately preceding character "c".
_Since “a ₅ ” is already registered under “ ₃ ”, the number of registered characters is extended by one character to “ab”, and “b” is registered under “a ₅ ”. However, as shown in FIG. 27A, since “b ₁₁ ” is already registered below “a ₅ ”, the number of registered characters is further extended by one character as shown in FIG. As “abb”, “b ₁₁ ”
"B" is registered in the lower order of "."

At this time, in the code tree, as shown in FIG. 28B, the node in which “ab” is registered is branched and “abb” is registered. This processing corresponds to the closed loop processing via the YES route of step E5, the YES route of step E10, and the YES route of step E25 of the processing steps described above with reference to FIG.

That is, when a character string is input, the combination of the immediately preceding character and one character in the input character string is
If already registered in the context tree, the number of characters to be registered is set to 1
Register only one unregistered character by expanding the character. At this time, in the code tree, the node of the escape code (ESC) registered together with the immediately preceding character is branched to create a new node, and this character string is registered.

As described above, the characters “abc abc a
When the input of "bb" is completed, the codes assigned to the characters are as shown in FIG. As shown in FIG. 29, the first input character "abc" is coded by one character alone, and the corresponding codes are 00,
It becomes 2 bits of 01 and 10.

Then, the next input character string "abc"
Is 1 bit of 0, 0, 0 from the relation with the immediately preceding character. Further, a code is assigned to the next input character string of "ab". As shown in FIG. 29, the character string of two characters is represented by a code word having only two bits.

The character "b" entered last is a case where there is no character corresponding to the connection of the immediately preceding character.
It is represented by three bits of a combination of ESC and a code word of one character alone. As described above, according to the data compression method of Related Art 1, characters (strings) to be compressed are registered by numbering a tree-structured context tree, and a code tree corresponding to the context tree is subjected to spray coding. By creating and updating while performing, a two-step process of constructing a probability model by calculating the appearance frequency of the appearing characters and assigning a code to each character is performed at the same time, greatly improving the speed of the data compression process. There is an effect of doing.

Since the above-described probability model is constructed by creating and updating (spray processing) a node of a code tree for each character input, the probability model already constructed for each character input is used. There is no need to perform an enormous amount of arithmetic processing of reconstruction, which has the effect of further improving the speed of the compression processing. Further, according to the data compression method of Related Technique 1, every time the same character as a previously compressed (encoded) character appears, a node of a code tree of the same character registered in the past is defined as an upper node. By rearranging (spray processing) the code length to １ ／, as the same character (string) repeatedly appears, the code of the character (string) can be represented by a smaller number of bits, so that the compression effect is greatly improved. effective.

Further, according to the data compression method of Related Art 1, as in the case where the above-described character string "ab" is encoded,
By encoding characters as character strings in units of a plurality of characters instead of encoding them in units of one character, the variable-length encoding process can be performed at high speed. This also has the effect that the coding efficiency of the spray coding is greatly improved.

(2) Description on the Decompression Side Next, as described above, the context collection process 21 in the data decompression device 2 described above with reference to FIG. The process in which the conversion process 22 restores data will be described with reference to processing steps D1 to D24 in the flowchart of FIG.

The process of restoring this data may basically be the reverse of the above-described coding process in the description of the coding side. That is, first, the context tree and the code tree are initialized, and the immediately preceding character P is initialized to 0 (step D1). The column length L is set to 0 (step D2),
It is checked whether there is a child node below the character immediately before the context tree (step D3).

Here, when there is no child node,
The character K is decoded using the input code as the 0-order code (step D).
From the NO route of No. 3 to step D4), it is checked whether or not the decoded character K is an EOF code (step D).
5). If the decoded character K is not an EOF code, a NO route is taken, the decoded character K is output (step D6), and the character K is registered in the context tree (step D).
7). This is performed in the same manner as in the encoding processing step E7 described above with reference to FIG.

Further, similarly to step E8 at the time of encoding, a node of a character K and an escape code is created below the character P immediately before the code tree (step D8), and the character P is set as the character K (step D17). ). Then, the subsequent processing steps D20 to D23 are the processing step E2 at the time of encoding.
The same processing steps as in steps 0 to E23 are performed, and the immediately preceding character string length L ′ is replaced with the noticed character string length L (step D2).
4), and return to the processing step D2 described above.

In the above-mentioned processing step D3, if a child node exists below the character P immediately before the context tree, the input code is decoded as a primary code from the code tree, and is decoded. The reference number of the character (string) is obtained (step D9 from the YES route of step D3). further,
It is checked whether the decrypted reference number is an escape code (step D10).
A YES route is taken, and the next code is decoded using the input character as the 0th order code to obtain a character K (step D11).

Then, similarly to the above-mentioned step D5, it is checked whether or not the decoded character K is an EOF code (step D12). Output (Step D
13). Furthermore, processing steps E13 to E15 at the time of encoding
In the same manner as described above, the character K is registered in the context tree (step D1).
4) Add a character K below the previous character P (step D1)
5) Update the escape code of the code tree and the code length of the zero-order code K as a spray code (step D16).

Thereafter, the processing from step D17 is performed. In this way, a splay code is assigned to every single character, and when a splay code of one character that does not exist in a character string in the dictionary already collected, a character string connected from the immediately preceding character is updated, the code is updated, and A connected decoded character from the character immediately before can be registered in the context tree.

In the processing step D10, if the decoded reference number is not an escape code,
By taking the NO route, the character string corresponding to the reference number of the context tree is restored and output (step D18), and the last character of the character (string) is replaced with the immediately preceding character P (step D19).
Thereafter, the processing from step D20 described above is performed.

Thus, as a dictionary registration character string,
It is possible to register the character string that has been decoded from the immediately preceding character and decode the character string that follows the immediately preceding character. If the decoded character K is the EOF code in the processing step D4 or step D12, a YES route is taken and the restoration processing is ended. As described above, the character strings of the data restored in the context tree as a dictionary are collected, numbered and registered, and the splay code is associated with each restored character string to correspond to the dictionary number. The character string is decoded and updated by the spray code, and an expanded character string of the encoded character string is registered until a predetermined maximum character string length is reached, and a spray code corresponding to the expanded character string is registered.

As a result, the character K compressed and encoded by the context collection step 11 and the spray encoding step 12 of the data compression device 1 is restored. As described above, according to the data restoration method of Related Art 1, characters (strings) restored in the context tree are numbered and registered, and a code tree as a code table corresponding to the context tree is constructed. ,
Since the two-stage process of searching the code table for a code that matches the code of the encoded character and outputting the character corresponding to the matched code as a decoded character is performed at the same time, the speed of the data restoration process is greatly increased. There is an effect of improving.

Further, since the above-described probability model is constructed by creating and updating (spray processing) a node of a code tree every time a character is restored, a code table that has already been constructed is restored every time a character is restored. There is no need to perform an enormous amount of computational processing of reconstructing the (probability model), which has the effect of further improving the speed of the restoration processing. Further, according to the data restoration method of Related Technique 1, every time the same code as the code decoded in the past appears, the node on the code tree of the same code registered in the past is recombined with the upper node ( Spray processing) By halving the code length, the code can be represented by a smaller number of bits as the same code appears repeatedly, so that when the same code is repeatedly decoded, the speed of the restoration process is greatly improved. is there.

Further, according to the data restoring method of Related Art 1, the spray processing can be sped up by decoding characters as character strings in units of a plurality of characters, instead of decoding them in units of one character. Is a character string, the information sources that can be restored are expanded, and the restoration efficiency is greatly improved. In the above-described example, the method of collecting and encoding / decoding a character string connected from the immediately preceding character as a context has been described. However, it is not always necessary to stick to the immediately preceding character, and the context from two or more characters before is collected and encoded. May be decrypted.

Further, in the above-described example, an example is shown in which contexts are dynamically collected and spray processing is performed. However, it is not necessarily dynamic, and a static context previously collected from a representative sample is used. Spray processing. Further, in the above-described example, a case has been described in which all input data is dynamically variable-length-encoded (spray-encoded). However, after encoding a considerable amount of data, the operation of updating the spray-encoding is stopped. Thus, static variable-length coding may be performed. In this case, it is sufficient that the encoding and the decoding are determined in advance and synchronized.

In the above-described example, the data to be compressed is described as a character or a character string. However, the data compression method and the data decompression method of Related Art 1 can be applied to any data such as other image data and audio data. it can. (B) Description of Technology 2 Related to the Present Invention Next, technology 2 related to the present invention (hereinafter referred to as “related technology 2”) will be described. First, the principle will be described.

FIG. 1 shows the configuration of an apparatus for implementing the data compression method according to Related Art 2. The data compression apparatus shown in FIG. 1 encodes and compresses input data according to a history that has appeared in the past. Here, 100 is a prefix data holding unit, 101 is a history holding unit, 102 is a code tree holding unit, 103 is a code tree determining unit, 104 is a code output unit, 105 is a code length changing unit, and 106 is a prefix data update unit. Means.

The prefix data holding means 100 holds a context composed of n pieces of input data input immediately before the input data, and the history holding means 101 holds a combination of the input data and the context. The code tree holding means 102 holds an independent code tree for each context. The code tree determining means 103 determines the code tree of the data from the input data up to just before being held in the prefix data holding means 100, and the code output means 104 selects the code tree by the code tree determining means 103 It outputs unique data according to a branch from a node as a branch point located halfway along a leaf where data is stored from the root meaning the vertex of the encoded code tree.

Further, the code length changing means 105 is for rearranging the coded leaf and another leaf or node, and the prefix data updating means 106 is for registering data in the prefix data holding means 100. is there. Also,
FIG. 2 shows the configuration of an apparatus for implementing another data compression method according to Related Art 2. The data compression device shown in FIG. 2 also encodes and compresses input data according to a history that has appeared in the past.

Here, 100 is a prefix data holding means, 1
01 is a history holding unit, 103 is a code tree determining unit, 107
Is a code tree determining means. Further, reference numeral 108 denotes a context determination unit, 109 denotes an escape code output unit, 110 denotes a context change unit, 111 denotes a code output unit, and 116 denotes a control unit. The prefix data holding means 100 holds a context consisting of n pieces of input data input immediately before the input data, and the history holding means 101 holds a combination of the input data and the context. In addition, the code tree holding unit 107 holds an independent code tree for each context in which an escape code defined as data indicating unregistered data is registered in advance.

The code tree determining means 103 determines the code tree of the data from the context and the input data. The context determining means 108 stores the data in the code tree determined by the code tree determining means 103. When no data is registered in the code tree, the escape code output means 109 determines whether or not the data is registered in the code tree from the root meaning the vertex of the code tree to the leaf as the data storage point of the escape code. The escape code is output according to the branch from the node as the branch point located.

Further, the context changing means 110 shortens the length n of the context when data is not registered in the code tree, and the code output means 111 outputs the data when the data is registered in the code tree. Outputs a code of data according to a branch from a node located halfway from the root of the code tree to the leaf of the data. The code length changing means 105 is for changing the coded leaf and another leaf or node.
Reference numeral 06 is for registering data in the prefix data holding means 100. When the escape code is encoded, the control means 116 repeats the processing until the data is encoded.

FIG. 3 shows the configuration of an apparatus for implementing another data compression method according to Related Art 2.
The data compression apparatus shown in FIG. 3 also encodes and compresses input data according to a history that has appeared in the past.
Here, 100 is a prefix data holding unit, 101 is a history holding unit, 103 is a code tree determining unit, 105 is a code length changing unit, 106 is a prefix data updating unit, 107 is a code tree holding unit, and 108 is a context determination. Means, 109 is an escape code output means, 110 is a context change means, 111 is a code output means, 112 is a history registration means, 113 is a code registration means, and 116 is a control means.

The prefix data holding means 100 holds a context consisting of n pieces of input data input immediately before the input data, and the history holding means 101 holds a combination of the input data and the context. The code tree holding unit 107 holds an independent code tree for each context in which an escape code defined as data indicating unregistered data is registered in advance.

The code tree determining means 103 determines the code tree of the data from the context and the input data. The context determining means 108 registers the data in the code tree determined by the code tree determining means 103. It is to determine whether or not there is. Furthermore, the escape code output means 109
When the data is not registered in the code tree, the escape code is output according to the branch from the node as a branch point located from the root meaning the top of the code tree to the leaf as the data storage point of the escape code. It is.

The history registering means 112 registers a combination of data and context in the history holding means 101 when no data is registered in the code tree. The code registering means 113 stores the data in the code tree. When the data is not registered, the data is newly registered in the code tree. When the data is not registered in the code tree, the context changing means 110 shortens the length n of the context.

Further, when data is registered in the code tree, the code output means 111 outputs the code of the data according to a branch from a node located halfway from the root of the code tree to the leaf of the data. , The code length changing means 105 is for changing the coded leaf and another leaf or node. The prefix data updating means 106 registers the data in the prefix data holding means 100, and the control means 116 repeats the processing until the data is encoded when the escape code is encoded. is there.

FIG. 4 shows the configuration of an apparatus for implementing still another data compression method according to Related Art 2. The data compression device shown in FIG. 4 also encodes and compresses input data according to a history that has appeared in the past. Here, 100 is a prefix data holding unit, 101 is a history holding unit, 103 is a code tree determining unit, 105 is a code length changing unit, 106 is a prefix data updating unit, 107 is a code tree holding unit, and 108 is a context determination. Means, 109 and 11
1 is an escape code output unit, 110 is a context change unit, 114 is a history registration unit, 115 is a code registration unit,
17 is a control means.

The prefix data holding means 100 holds the context consisting of n pieces of input data input immediately before the input data, and the history holding means 101 holds the combination of the input data and the context. The code tree holding means 107 holds an independent code tree for each context in which an escape code defined as data indicating data not registered is registered in advance.

The code tree determining means 103 determines the code tree of the data from the context and the input data. The context determining means 108 registers the data in the code tree determined by the code tree determining means 103. It is to determine whether or not there is. Furthermore, the escape code output means 109
When the data is not registered in the code tree, the escape code is output according to the branch from the node as a branch point located halfway from the root meaning the top of the code tree to the leaf as the data storage point of the escape code. It is.

The context changing means 110 shortens the length n of the context when data is not registered in the code tree, and the escape code output means 111 stores data in the code tree. At the time, the code of the data is output according to the branch from the node located halfway from the root of the code tree to the leaf of the data. Further, the history registration unit 114 registers a combination of data and context in the history holding unit 101, the code registration unit 115 newly registers data in the code tree, and the code length change unit 105 , The encoded leaf is replaced with another leaf or node, and the prefix data updating means 106 registers the data in the prefix data holding means 100.

If the escape code has been encoded at least once at the time of encoding the data, the control means 117 stores the combination of the context and the data immediately before the encoding of the data in the history holding means 101 by the history registering means 114. The data is newly registered by the code registration unit 115 in a code tree having an escape code which has been registered and coded immediately before the data is coded.

On the other hand, FIG. 5 shows the configuration of an apparatus for implementing the data restoration method according to Related Art 2. The data restoration apparatus shown in FIG. 5 decodes a code coded according to a history that has appeared in the past. Here, 200 is a prefix data holding unit, 201 is a history holding unit, 202 is a code tree holding unit, 203 is a code tree determining unit, 204 is a decoding unit, 205 is a code length changing unit, and 206 is a prefix data updating unit. It is.

The prefix data holding means 200 holds n pieces of data decoded in the past, and the history holding means 201 holds a combination of the decoded data and the context. The means 202 holds an independent code tree for each context. The code tree determining means 203 determines a code tree for decoding data from the context held in the prefix data holding means 200, and the decoding means 204 determines the code tree according to the code. It scans a node as a branch point from the root meaning the selected code tree vertex and outputs data stored in a leaf as a data storage point reached.

Further, the code length changing means 205 is for rearranging the decoded leaf with another leaf or node, and the prefix data updating means 206 is for registering the decoded data in the prefix data holding means 200. It is.
FIG. 6 shows a configuration of an apparatus for performing another data restoration method according to Related Art 2. The data restoration apparatus shown in FIG. 6 also decodes a code coded according to a history that has appeared in the past.

Here, 200 is a prefix data holding means, 2
01 is a history holding unit, 203 is a code tree determining unit, 204
Is a decoding unit, 205 is a code length changing unit, 206 is a prefix data updating unit, 207 is a code tree holding unit, 208 is a context changing unit, and 213 is a control unit. The prefix data holding means 200 holds n data decoded in the past, the history holding means 201 holds a combination of decoded data and context, and the code tree holding means 207 , Which holds a code tree in which an escape code defined as data indicating data not registered is registered in advance.

The code tree determining means 203 determines a code tree for decoding data from the context held in the prefix data holding means 200.
Reference numeral 04 denotes a node which scans a node as a branch point from a root meaning a vertex of the code tree selected by the code tree determining means 203 according to a code and outputs data stored in a leaf as a data storage point reached. is there.

Further, the code length changing means 205 is for recombining the decoded leaf with another leaf or node. When the output data is an escape code, the data is rejected and the context is changed. The prefix data updating means 206 registers the decrypted data in the prefix data holding means 200.

When the escape code is decoded, the control means 213 resets the context by the context changing means 208, and repeats the processing until a code other than the escape code is decoded. FIG. 7 shows a configuration of an apparatus for performing still another data restoration method according to Related Art 2. The data restoration device shown in FIG. 7 also decodes a code coded according to a history that has appeared in the past.

Here, 200 is a prefix data holding means, 2
01 is a history holding unit, 203 is a code tree determining unit, 204
Is a decoding unit, 205 is a code length changing unit, 206 is a prefix data updating unit, 207 is a code tree holding unit, 208 is a context changing unit, 209 is a history registering unit, 210 is a code registering unit, and 213 is a control unit. . Prefix data holding means 20
0 holds n pieces of data decoded in the past, the history holding means 201 holds a combination of the decoded data and the context, and the code tree holding means 20
Reference numeral 7 stores a code tree in which escape codes are registered in advance.

The code tree determining means 203 determines a code tree for decoding data from the context held in the prefix data holding means 200.
Reference numeral 04 denotes a node which scans a node as a branch point from a root meaning a vertex of the code tree selected by the code tree determining means 203 according to a code and outputs data stored in a leaf as a data storage point reached. is there.

Further, the code length changing means 205 is for rearranging the decoded leaf with another leaf or node. When the output data is the above escape code, the context changing means 208 rejects the data. And to shorten the context. Further, the prefix data updating unit 206 stores the decrypted data in the prefix data holding unit 200.
The history registration unit 209 registers all contexts and decoded data when the escape code is decoded in the data decoding process in the history holding unit 201.

The code registering means 210 registers the code of the data in all the code trees corresponding to the context when the escape code is decoded in the data decoding process.
When the escape code is decoded, the control means 213 resets the context by the context change means 208, and repeats the processing until a code other than the escape code is decoded.

FIG. 8 shows the configuration of an apparatus for implementing another data restoration method according to Related Art 2.
The data restoration device shown in FIG. 8 also decodes a code encoded according to a history that has appeared in the past. Here, 200 is a prefix data holding unit, 201 is a history holding unit, 203 is a code tree determining unit, 204 is a decoding unit, 20
5 is code length changing means, 206 is prefix data updating means, 2
07 is a code tree holding unit, 208 is a context change unit, 212
Denotes a code registration unit, and 213 denotes a control unit.

The prefix data holding means 200 holds n data decoded in the past, and the history holding means 201 holds a combination of the decoded data and the context. The means 207 holds a code tree in which an escape code defined as data indicating data not registered is registered in advance. Also,
The code tree determining means 203 determines a code tree for decoding data from the context held in the prefix data holding means 200, and the decoding means 204 selects the code tree in accordance with the code. It scans a node as a branch point from a root meaning a vertex of a code tree and outputs data stored in a leaf as a data storage point reached.

Further, the code length changing means 205 is for rearranging the decoded leaf with another leaf or node. When the output data is an escape code, the data is rejected and the context is changed. The prefix data updating means 206 registers the decrypted data in the prefix data holding means 200.

The history registering means 211 registers the context when the escape code was last decoded in the data decoding process and the decoded data in the history holding means 201. Registering the code of the data in the code tree corresponding to the context when the escape code was decoded last in the decoding process of
Reference numeral 13 indicates that when the escape code is decoded, the context is reset by the context changing means 208, and the process is repeated until a code other than the escape code is decoded.

In a device having the configuration described with reference to FIG. 1, that is, a data compression device that encodes and compresses input data in accordance with a history that has appeared in the past, the front data holding unit 100 stores the input data. , The history holding means 101 holds a combination of the input data and the context, and the code tree holding means 102 stores an independent code tree for each context. Hold.

The code tree determining means 103 determines the code tree of the data from the input data up to just before being held in the prefix data holding means 100, and outputs the code tree.
Outputs unique data in accordance with a branch from a node serving as a branch point located halfway along a leaf in which data is stored from the root meaning the vertex of the code tree selected by the code tree determination unit 103.

Further, the code length changing means 105 rearranges the coded leaf with another leaf or node,
The prefix data updating means 106 can register the data in the prefix data holding means 100. Next, in an apparatus having the configuration described with reference to FIG. 2, that is, in a data compression apparatus that encodes and compresses input data according to a history that has appeared in the past, the prefix data holding unit 100 is configured The history holding unit 101 holds a combination of the input data and the context, and the code tree holding unit 107
An independent code tree is stored for each context in which an escape code defined as data indicating data not registered is registered in advance.

Then, the code tree determining means 103 determines the code tree of the data from the context and the input data, and the context determining means 108 determines whether or not the data is registered in the code tree determined by the code tree determining means 103. When the data is not registered in the code tree, the escape code output means 109 determines that the branch point located halfway from the root meaning the vertex of the code tree to the leaf as the data storage point of the escape code. Output escape code according to branch from node.

Further, the context changing means 110 shortens the length n of the context when no data is registered in the code tree, and the code output means 111 sets the code tree when data is registered in the code tree. A code of data is output in accordance with a branch from a node located halfway from the root of the data to a leaf of the data, and the code length changing means 105 rearranges the encoded leaf with another leaf or node.

Then, the prefix data updating means 106 registers the data in the prefix data holding means 100 and the control means 1
16 encodes the escape code, and repeats the process until the data is encoded. Next, in an apparatus having the configuration described with reference to FIG. 3, that is, in a data compression apparatus that encodes and compresses input data according to a history that has appeared in the past, the pre-data holding unit 100 is configured The history holding unit 101 holds a combination of the input data and the context, and the code tree holding unit 107
An independent code tree is stored for each context in which an escape code defined as data indicating data not registered is registered in advance.

Then, the code tree determining means 103 determines the code tree of the data from the context and the input data, and the context determining means 108 determines whether or not the data is registered in the code tree determined by the code tree determining means 103. When the data is not registered in the code tree, the escape output means 109 determines whether the node as a branch point located from the root indicating the vertex of the code tree to the leaf as the data storage point of the escape code. Output escape code according to branch from. Further, when data is not registered in the code tree, the history registration unit 112 registers a combination of data and context in the history holding unit 101, and the code registration unit 11
3 newly registers data in the code tree when no data is registered in the code tree, and the context changing means 110 shortens the length n of the context when no data is registered in the code tree; When data is registered in the code tree, the code output unit 111 outputs the code of the data according to a branch from a node located halfway from the root of the code tree to the leaf of the data.

Then, the code length changing means 105 rearranges the coded leaf with another leaf or node,
The prefix data updating unit 106 registers the data in the prefix data holding unit 100, and when the control unit 116 encodes the escape code, the process is repeated until the data is encoded. Next, in a device having the configuration described with reference to FIG. 4, that is, in a data compression device that encodes and compresses input data according to a history that has appeared in the past, the pre-data holding unit 100 determines whether the input data The history holding means 101 holds a combination of the input data and the context, and the code tree holding means 107 is defined as data indicating that data has not been registered. An independent code tree is stored for each context in which escape codes are registered in advance.

Then, the code tree determining means 103 determines the code tree of the data from the context and the input data, and the context determining means 108 determines whether or not the data is registered in the code tree determined by the code tree determining means 103. If no data is registered in the escape code output means 109 and the code tree, a node as a branch point located halfway from the root meaning the vertex of the code tree to a leaf as a data storage point of the escape code Output escape code according to branch from.

Further, the context changing means 110 shortens the length n of the context when data is not registered in the code tree, and the escape code output means 111 sets the code length when data is registered in the code tree. The code of the data is output according to a branch from a node located halfway from the root of the tree to the leaf of the data. And the history registration means 11
4 registers the combination of the data and the context in the history holding unit 101, the code registration unit 115 newly registers the data in the code tree, and the code length changing unit 105 stores the coded leaf and another leaf or node. And the prefix data updating means 106 stores the data in the prefix data holding means 10.
Register to 0.

Further, when the control means 116 encodes the escape code even once at the time of encoding the data,
The combination of the context and the data immediately before the encoding of the data is registered in the history holding unit 101 by the history registering unit 114, and the data is stored in the code tree having the escape code encoded immediately before the encoding of the data by the code registering unit 115. Is newly registered.

On the other hand, in an apparatus having the configuration described with reference to FIG. 5, that is, in a data restoration apparatus that decodes a code coded according to a history that has appeared in the past, the pre-data holding unit 200 uses the previously decoded data. The history holding unit 201 holds the combination of the decoded data and the context, and the code tree holding unit 202 holds an independent code tree for each context.

Then, the code tree determining means 203 determines a code tree for decoding data from the context held in the prefix data holding means 200, and the decoding means 204 causes the code tree determining means 203 to follow the code. A node serving as a branch point is scanned from a root meaning a vertex of the selected code tree, and data stored in a leaf serving as a data storage point reached is output.

Further, code length changing means 205 rearranges the decoded leaf with another leaf or node, and prefix data updating means 206 registers the decoded data in prefix data holding means 200. Next, in an apparatus having the configuration described with reference to FIG. 6, that is, in a data restoration apparatus that decodes a code coded according to a history that has appeared in the past, the pre-data holding unit 200 uses the previously decoded n And the history holding means 201 holds the combination of the decoded data and the context, and the code tree holding means 2
07 holds a code tree in which an escape code defined as data indicating unregistered data is registered in advance.

Then, the code tree determining means 203 determines a code tree for decoding data from the context held in the prefix data holding means 200, and the decoding means 204 causes the code tree determining means 203 to follow the code. A node serving as a branch point is scanned from a root meaning a vertex of the selected code tree, and data stored in a leaf serving as a data storage point reached is output.

Further, the code length changing means 205 rearranges the decoded leaf with another leaf or node, and the context changing means 208 rejects the data when the output data is an escape code to shorten the context, The prefix data updating means 206 registers the decrypted data in the prefix data holding means 200. Then, when the control means 213 decodes the escape code, the context is changed by the context changing means 208, and the process is repeated until a code other than the escape code is decoded.

Next, in an apparatus having the configuration described with reference to FIG. 7, that is, in a data restoration apparatus that decodes a code coded according to a history that appeared in the past, the pre-data holding means 200 The n pieces of decoded data are held, the history holding unit 201 holds a combination of the decoded data and the context, and the code tree holding unit 207 holds a code tree in which escape codes are registered in advance.

Then, the code tree determining means 203 determines a code tree for decoding data from the context held in the prefix data holding means 200, and the decoding means 204 determines the code tree in accordance with the code. A node serving as a branch point is scanned from a root meaning a vertex of the selected code tree, and data stored in a leaf serving as a data storage point reached is output.

Further, the code length changing means 205 rearranges the decoded leaf and another leaf or node, and the context changing means 208 discards the data and shortens the context when the output data is an escape code. , The prefix data updating means 206 registers the decrypted data in the prefix data holding means 200. Then, the history registration means 209
Stores all contexts when the escape code is decoded in the data decoding process and the decoded data in the history holding unit 20.
1 and the code registration unit 210 registers the code of the data in all the code trees corresponding to the context when the escape code is decoded in the data decoding process.
When the escape code is decoded, the context is reset by the context changing unit 208, and the process is repeated until a code other than the escape code is decoded.

Next, in an apparatus having the configuration described with reference to FIG. 8, that is, in a data restoration apparatus that decodes a code coded according to a history that has appeared in the past, the prefix data holding means 200 The history holding means 201 holds the decoded n data, the history data holding means 201 holds the combination of the decoded data and the context, and the code tree holding means 207 pre-registers an escape code defined as data indicating data not registered. The code tree that has been set is retained.

The code tree determining means 203 determines a code tree for decoding data from the context held in the prefix data holding means 200, and the decoding means 204 determines the code tree according to the code. A node serving as a branch point is scanned from a root meaning a vertex of the selected code tree, and data stored in a leaf serving as a data storage point reached is output.

Further, the code length changing means 205 rearranges the decoded leaf with another leaf or node, and the context changing means 208 rejects the data when the output data is an escape code and shortens the context. Then, the prefix data updating means 206 registers the decrypted data in the prefix data holding means 200 and the history registration means 211
Is used to store the context when the escape code was last decoded in the data decoding process and the decoded data in the history holding unit 201.
, And the code registration unit 212 registers the code of the data in the code tree corresponding to the context when the escape code was decoded last in the data decoding process.

Further, when the control means 213 decodes the escape code, the context is changed by the context changing means 208, and the process is repeated until a code other than the escape code is decoded.

Therefore, according to the data compression method according to Related Art 2 described above, a probability model is constructed by calculating the appearance frequency of input data, a code is assigned to each input data, and a code table is created. The two-stage process of outputting the code of the character to be encoded can be performed simultaneously, which has the effect of greatly improving the speed of the compression process. Further, it is possible to omit an enormous amount of arithmetic processing for reconstructing a probability model that has already been constructed every time data is input, thereby further improving the speed of compression processing. Furthermore, as the same data as the input data that appeared in the past repeatedly appears, the sign of the data can be represented by a smaller number of bits, which also has the effect of greatly improving the compression effect in data compression.

When the combination of the input data and the context is a combination that is not stored in the history of the context collection process, an escape code is output, and the data is output until the combination stored in the context collection process is obtained. The process of shortening the context is repeated, and in addition to the above-mentioned effects, it is not necessary to register all the histories of the combination of the input data and the context in advance, thereby greatly improving the data compression processing speed. Has the effect of doing Further, it is possible to shorten the time until the combination of the input data and the context is obtained, which has the effect of greatly improving the data compression processing speed.

In addition, input data that has not been registered in the past can be newly registered, and the newly registered data can be encoded at an early stage in the next encoding process. As a result, there is an effect that the data compression effect is greatly improved as the encoding process proceeds.

Furthermore, in the context new registration process and the code tree new registration process, only the combination of the context and the data immediately before that is determined to be in the history is registered, so that it is determined that the combination is not in the history of the past input data. It is not necessary to register all the combinations of the context and the data, which has the effect of greatly improving the data compression processing. Furthermore, a code can be assigned (registered) only for data that actually has a high frequency of appearance, which has the effect of greatly improving the data compression efficiency.

On the other hand, according to the data restoration method according to Related Art 2 described above, a probability model is constructed by determining the appearance frequency of input data, a code is assigned to each input data, and a code table is created. The two-stage process of outputting the character to be decoded can be performed simultaneously, which has the effect of greatly improving the speed of the data restoration process. Further, it is possible to omit an enormous amount of arithmetic processing of reconstructing a probability model that has already been constructed each time data is input, thereby further improving the speed of restoration processing. Further, as the code of the same data as the code of the input data that has appeared in the past repeatedly appears, the code of the data can be represented by a smaller number of bits, which also has the effect of greatly improving the restoration effect in data restoration. .

Further, in the code tree, an escape code defined as data indicating that data is not registered is registered in advance for each code tree corresponding to each context, and when the escape code is decoded at the time of decoding, only the escape code other than the escape code is decoded. Until the context is shortened,
It is not necessary to register all the histories of the combination of the decoded data and the context in advance, and this has the effect of greatly improving the processing speed of data restoration. Further, it is possible to shorten the time until the combination of the decoded data and the context is obtained, which has the effect of greatly improving the data restoration processing speed.

When an escape code defined as data indicating that data has not been registered is decoded, the context new registration process and the code tree new registration process are executed, and the length of the context is decoded until anything other than the escape code is decoded. Is repeated, so that decoded data that has not been registered in the past can be newly registered, and the newly registered decoded data can be decoded at an early stage in the next decoding process. As a result, the effect of restoring data is greatly improved as the decoding process proceeds.

Further, in the processing until the escape code other than the escape code defined as the data indicating that the data has not been registered is decoded, when at least one escape code is decoded,
Each new registration process in the context new registration process and the code tree new registration process is performed only in the context immediately before decoding other than the escape code, so the combination of the context and the data determined not to be in the past input data history Does not need to be registered, and this has the effect of greatly improving the processing speed of data restoration. Furthermore, a code can be assigned (registered) only to data that actually has a high frequency of appearance, which has the effect of greatly improving data restoration efficiency.

Further, according to another data compression apparatus according to Related Technique 2, a probability model is constructed by determining the appearance frequency of input data, a code is assigned to each input data, and a code table is created. The two-stage process of outputting the code of the data to be encoded can be performed simultaneously, which has the effect of greatly improving the data compression processing speed. Further, it is possible to omit an enormous amount of arithmetic processing for reconstructing a probability model that has already been constructed each time data is input, thereby further improving the processing speed of data compression. Also, the code length can be changed by rearranging the coded leaf and another leaf or node every time the same data as the previously coded data appears. The sign of the data can be represented by a small number of bits, which also has the effect of significantly improving the data compression effect.

Further, since it is not necessary to register all the histories of the combination of the input data and the context in advance, the processing speed of the data compression is greatly improved, and the memory used for the registration of the context is greatly increased. Since the processing load can be reduced, the processing load of the data compression apparatus can be significantly reduced.

Further, input data that has not been registered in the past can be newly registered, and
This newly registered data can also be encoded at an early stage in the next encoding process, so that as the encoding process progresses, the data compression effect is greatly improved and the processing load of the data compression device is also increased. There is an effect that can be reduced.

Furthermore, it is not necessary to register all combinations of contexts and data determined not to be in the history of past input data, which has the effect of greatly improving data compression processing. Furthermore, a code can be assigned (registered) only for data that actually has a high frequency of appearance, which has the effect of greatly improving the data compression efficiency. The effect described above has the effect of dramatically improving the performance of the data compression device.

Further, according to the data restoration apparatus according to the related art 2, the appearance frequency of the input data is obtained, a probability model is constructed, a code is assigned to each input data, and a code table is created.
The two-stage process of outputting a character to be decoded from this code table can be performed simultaneously, which has the effect of greatly improving the speed of the data restoration process. Further, it is possible to omit an enormous amount of arithmetic processing of reconstructing a probability model that has already been constructed each time data is input, thereby further improving the speed of restoration processing. Further, as the code of the same data as the code of the input data that has appeared in the past repeatedly appears, the code of the data can be represented by a smaller number of bits, which also has the effect of greatly improving the restoration effect in data restoration. . The effect described above has the effect of dramatically improving the performance of the data restoration device.

Further, it is not necessary to register all the histories of the combination of the decoded data and the context in advance, which has the effect of greatly improving the data restoration processing speed. Further, the time until the combination of the decoded data and the context is obtained can be shortened, whereby the processing speed of the data restoration is greatly improved, and the performance of the data restoration device is also greatly improved.

Also, it is possible to newly register the decoded data which has not been registered in the past, and to decode the newly registered decoded data at an early stage in the next decoding processing. As the decryption process progresses, the effect of restoring data greatly improves,
This has the effect of greatly improving the performance of the data restoration device.

Furthermore, it is not necessary to register all combinations of contexts and data determined not to be in the history of past input data, which has the effect of greatly improving data restoration processing. Furthermore, a code can be assigned (registered) only to data that actually has a high frequency of appearance, which has the effect of greatly improving the data recovery efficiency and greatly improving the performance of the data recovery device. Next, the related art 2 will be described more specifically. FIG. 32 is a block diagram illustrating a configuration example of a data compression device and a data decompression device for performing the data compression method and the data decompression method according to the related art 2.
, The data compression device 3 encodes and compresses the input data according to the history that has appeared in the past, and the data decompression device 4 decodes the code encoded by the data compression device 3. is there.

Hereinafter, the data compression device 3 will be described as an encoding side, and the data decompression device 4 will be described as a decompression side. In addition,
In the following description, the context tree and the code tree have the configuration described in Related Art 1. (1) Description on the Encoding Side FIG. 33 is a block diagram showing an example of the internal configuration of the data compression device 3 described above. As shown in FIG.
A-1 to 100A-n (n is a natural number) are a prefix data holding unit, 101A is a context history holding unit, 102A is a code tree holding unit, 103A is a code tree determining unit, 104A is an encoding unit,
05A is a code tree updating unit, and 106A is a context updating unit.

Here, the prefix data holding units (prefix data holding means) 100A-1 to 100A-n are provided with n input immediately before the input data K (hereinafter, sometimes referred to as event K). It holds the context consisting of data. Also, a context history holding unit (history holding unit) 101A
Holds a combination of input data K and a context, and includes a code tree holding unit (code tree holding unit) 102
A holds an independent code tree for each context,
The code tree determination unit (code tree determination unit) 103A determines a code tree from data immediately before stored in the prefix data storage units 100A-1 to 100A-n.

Further, the encoding section (code output means) 104
A encodes the data K and starts from the root of the code tree (the vertex of the code tree) selected by the code tree determination unit 103A.
Outputs data K encoded according to a branch from a node (branch point) located halfway along the leaf in which is stored. The code tree updating unit (code length changing unit) 105A is for rearranging the coded leaf and another leaf or node, and the context updating unit (prefix data updating unit) 106A adds the data K to the prefix. It is registered in the data holding units 100A-1 to 100A-n.

FIG. 34 shows the encoding section 104A.
34 is a block diagram showing an example of the internal configuration of the encoding unit 104A, as shown in FIG. 34, in order to output data K encoded according to the branch from the node as described above.
Includes an upper node determining unit 41, a node number managing unit (memory) 42, a position determining unit 43, a latch 44, and a stack 45.
Is provided.

Here, the upper node discriminating section 41 obtains the node number of the upper node from the node number of the root of the code tree and the node number of the leaf of the context tree. The node number management section (memory) 42 , And manages the node numbers of the context tree and the code tree, and the position determining unit 43 determines the branch state of the node. Further, the latch 44
Holds the node number of the leaf once, and the stack 45 stores the data K output from the position determination unit 43.
Are temporarily stored, and when the end signal is received, the stored codes are sequentially output.

With the above configuration, in the data compression apparatus shown in FIG. 33, the prefix data holding units 100A-1 to 100A
−n holds a context composed of n pieces of input data input immediately before the input data K, and a context history holding unit 101
A holds a combination of input data and a context, and the code tree holding unit 102A holds an independent code tree for each context.

Further, the code tree determining unit 103A determines a code tree of the data from the input data up to just before being held in the prefix data holding units 100A-1 to 100A-n.
The coding unit 104A outputs “0” or “1” according to a branch from a node located halfway along the leaf storing the data K from the root (vertex) of the code tree selected by the code tree determination unit 103A. The code (unique data) represented is output.

Further, the code tree updating unit 105A as a code length changing unit rearranges the encoded leaf with another leaf or node, and the prefix data updating unit 106A stores the data K in the prefix data holding unit 100A-. Register to 1.
Here, the above operation will be described in more detail with reference to processing steps A1 to A6 in the flowchart shown in FIG.

First, the prefix data holding units 100A-1 to 100A-1
The context character string P held in 00A-n is initialized (step A1), and data K to be encoded is input (step A2). The code tree determining unit 103A sends the context P from the context history holding unit 101A holding the history of the context held in the prefix data holding units 100A-1 to 100A-n.
Is determined, and the node number (ID) of the leaf holding the data K and the node number (ID) of the root of the context P are determined from the determined code tree and the information of the context history holding unit 101A. To the encoding unit 104A,
4A is the event K in the code tree corresponding to the context P.
A code corresponding to the branch of the node from the leaf of (data K) to the root is output (step A3). The processing performed by encoding section 104A will be described later in detail with reference to FIG.

After the encoding in encoding section 104A, code tree updating section 105A rearranges the leaf of event K in the code tree with another leaf or node (step A).
4) Update the code tree by storing it in the original code tree holding unit 102A. The process performed by the code tree updating unit 105A will be described later in detail with reference to FIG.

Further, context update section 106A rejects the oldest data (data held in prefix data holding section 100-n) and registers input data K as a context in prefix data holding section 100A-1. By doing, the context string P
Is updated (step A5). Then, it is checked whether encoding is completed for all data (step A).
6) If not completed, the processing from step A2 is repeated, and if completed, the encoding processing ends (YES route of step A6).

The above-described processing for changing the nodes (step A4) and the processing for updating the context (step A5) may be performed first, or may be performed in parallel. next,
As described in the processing step A3, the encoding processing performed by the encoding unit 104A having the configuration described above with reference to FIG. 34 will be described with reference to processing steps B1 to B8 in FIG.

First, the stack 45 (push-down)
stack) is initialized (step B1), and the address pointer of the current node L is set to a leaf in the code tree of the context P in which the data K is stored (step B2). And it was sent in the above-mentioned step A3,
Node number (ID) of leaf holding data K
Is sent from the latch 44 to the position determining unit 43, and the position determining unit 43 sends information on which of the upper nodes the node of the received node number is located to the node number managing unit 42.
It is determined whether the node received from this information is located on the right hand of the upper node (step B3).

If the right hand is located, “1” is set to stack 4
Push (output) to No. 5 (step B4 from the YES route of step B3), and if it is located on the left hand, push (output) "0" to the stack 45 (step B5 from the NO route of step B3). Further, the node number (ID) of the root of the context P, which is another node number, sent in step A3 described above is sent to the upper node determining unit 41, and the upper node determining unit 41 transmits the received node ( It is determined whether or not the leaf is the root (step B6).

If the route is a route, an end signal is output (YES route in step B6). If the route is not a route, the node number (ID) management unit 42 is accessed, and the upper level of this node (or leaf) is accessed. , The node (U) is newly obtained as the current node L, the address pointer is moved to the upper node, and the processing from step B3 is repeated (from the NO route of step B6 to step B7). .

By repeating the processing until the address pointer reaches the root in this way, the "path" represented by the numerical value of "1" or "0" from the leaf to the root is stored in the stack 45. You. And this "path",
Conversely, by outputting one bit at a time from the lower bits (pop-up output), the "path" from the root to the leaf is output as a code (step B8).

Next, as described above in the processing step A4, the code tree updating unit 105A performs the process of rearranging the leaf of the event K with another leaf or node as shown in FIG.
This will be described in detail with reference to the processing steps C1 to C9. First, the address pointer of the node Z to be rearranged is set in the leaf K (step C1), and the upper node of the node Z is set in the node U0 (step C2).

Then, it is determined whether or not the upper node U0 of K is the root of the code tree (step C3). If it is the root, the rearrangement is terminated (YES from step C3 to step C9). The upper node of the node U0 is set to U1 (NO in step C3)
From the root, step C4), it is determined whether the node U0 is located with respect to the upper node U1 of the node U0 (step C5).

If U0 is to the right of U1, node X
Is set to the node located to the left of node U1 (from the YES route of step C5 to step C6), and the node Z
And node X (step C8). That is, the node on the left of the node U1 and the leaf K are rearranged. On the other hand, when the node U0 is on the left hand side of U1, a node located on the right hand side of the node U1 is set to the node X (step C7 from the NO route of step C5), and the node Z is replaced with the node X (step C8). . That is, the node on the right side of the node U1 and the leaf K are rearranged.

Further, when the address pointer of the node Z is set to the node U1 (step C9), the process returns to the above-mentioned step C2. In step C3, the upper node of the set address pointer is the root, that is, the address pointer is immediately below the root. The process is repeated until the node is determined. By performing this processing, the distance (code length) of the accessed leaf from the root is halved.

By repeating the above processing for all input characters, a character string can be encoded. As described above, according to the data compression apparatus for performing the data compression method according to the related art 2, the character to be encoded is
A number is assigned to the context tree of the tree structure and registered, and a code tree corresponding to the context tree is created and updated while performing the splay coding, thereby obtaining a frequency of appearance of a character to construct a probability model. A code table is created by assigning a code to each character, and the two-stage process of outputting the code of the character to be coded from this code table can be performed at the same time. is there.

Further, as described above, a probability model is constructed by creating / updating (spray processing) a node of a code tree every time a character is input. Since an enormous amount of arithmetic processing for reconstructing the model can be omitted, the speed of the compression processing is further improved. Further, every time the same character as the previously compressed (encoded) character appears, the code tree node of the same character registered in the past is recombined with the upper node to reduce the code length to （( By performing the spray processing, the sign of the character (string) can be represented by a smaller number of bits as the same character (string) repeatedly appears, so that the compression effect is greatly improved.

(2) Description on the Restoration Side FIG. 38 is a block diagram showing an example of the internal configuration of the data restoration apparatus 4 described above. As shown in FIG.
A-1 to 200A-n (n is a natural number) are a prefix data holding unit, 201A is a context history holding unit, 202A is a code tree holding unit, 203A is a code tree determining unit, 204A is a coding unit,
05A is a code tree updating unit, and 206A is a context updating unit.

Here, the prefix data holding sections (prefix data holding means) 200A-1 to 200A-n hold n pieces of data decoded in the past, and are stored in the context history holding section (history holding means). ) 201A holds a combination of a decoded symbol and a context, and a code tree holding unit (code tree holding means) 202A holds an independent code tree for each context.

A code tree determining unit (code tree determining means) 2
03A is a prefix data holding unit 200A-1 to 200A-
n to determine a code tree for decoding a symbol from the context held in the decoding unit (decoding means) 20
4A is a node (branch point) from the root (the top of the code tree) of the code tree selected by the code tree determination unit 203A according to the code.
To output the symbols stored in the reached leaf.

Further, a code tree updating unit (code length changing means)
205A is for rearranging the decoded leaf with another leaf or node, and the context updating unit (prefix data updating unit) 206A registers the decoded symbol in the prefix data holding units 200A-1 to 200A-n. Is what you do. FIG. 39 is a block diagram showing an example of the internal configuration of the above-described decoding unit 204A. As shown in FIG. 39, nodes are scanned from the root of the code tree selected by the code tree determination unit 203A according to the code. In order to output the symbol stored in the leaf that has arrived, the decoding unit 204A
Includes a node number management unit (memory) 42 and a latch 44
, A lower node discriminator 46 and a leaf / node discriminator 47 are provided.

Here, the node number management unit (memory) 42
Is the same as described above with reference to FIG. 34 in the description of the encoding side, and manages the node numbers of the context tree and the code tree. Further, the lower node determining unit 46 includes a code and a node number of the root of the code tree and a node number management unit 42.
The node number of the lower node is obtained from the information of
The leaf / node discriminating section 47 discriminates whether the lower node is a leaf or a node from the information from the lower node discriminating section 46 and the node number managing section 42, and the latch 48 temporarily holds the root node number. Things.

With the above-described configuration, the pre-data holding units 200A-1 to 200A-n use the previously decoded n
Context (data) is stored in the context history storage unit 201A.
Holds the combination of the decoded data K and the context, and the code tree holding unit 202A holds an independent code tree for each context. Further, the code tree determining unit 203A determines a code tree for decoding the data K from the context held in the prefix data holding units 200A-1 to 200A-n, and the decoding unit 204A A node (branch point) is scanned from the root (vertex) of the code tree selected by the code tree determination unit 203A according to the code of the data K, and the data K stored in the leaf reached is output.

Further, the code tree updating unit 205A as code length changing means rearranges the decoded leaf with another leaf or node, and the prefix data updating unit 206A uses the decoded data K as the prefix in the latest context. Data holding unit 20
Register at 0A-1. Hereinafter, the above processing will be described with reference to FIG.
0 will be described in more detail with reference to processing steps F1 to F6 in the flowchart shown in FIG.

First, the prefix data holding units 200A-1 and 200A-2
Initialize n context character strings P held in 00A-n (step F1), and input an event (data) K to be decoded (step F2). The code tree determining unit 203A is a context history holding unit 201A that holds the history of the context held in the prefix data holding units 200A-1 to 200A-n.
, And sends the node number (ID) of the root of the determined code tree and the code of the event K to be decoded to the decoding unit 204A, and the decoding unit 204A In accordance with the transmitted code, the root is scanned to the leaf storing the event K to decode the code (step F3). Note that this decoding unit 204
The processing performed by A will be described later in detail with reference to FIG.

Then, after decoding, the code tree updating unit 205A
Updates the code tree by assembling the leaf of the event K decoded by the code tree with another leaf or node (step F4), and storing it in the original code tree holding unit 202A.
The node rearrangement process performed by the code tree updating unit 205A is performed in the same manner as the processing steps C1 to C9 performed by the code tree updating unit 105A described above with reference to the flowchart of FIG.

Further, the context update unit 206A rejects the oldest data (data held in the prefix data holding unit 200-n), and uses the decoded event (data) K as a context and adds the event (data) K to the prefix data holding unit 200A. By registering it as -1, the context character string P is updated (step F5). Then, it is checked whether the decoding has been completed for all data (step F6). If not completed, the processing from step F2 is repeated (NO route of step F6), and if not, the decoding processing is ended (step F6). F6 YES route).

In this case, as in the case of the encoding side, either of the above-described processing of changing the node (step F4) and updating of the context (step F5) may be performed first.
Processing may be performed in parallel. Next, as described in the processing step F3, the decoding unit 204 having the configuration described above with reference to FIG.
The encoding process performed by A will be described with reference to processing steps G1 to G7 in the flowchart shown in FIG.

First, the lower node discriminating unit 46 determines the node number (I
D) is set to node Z (step G1), and latch 4
The code (1 bit) of the event K to be decoded, which is also sent from the code tree determination unit 203A via the code No. 8, is set to C (step G2). Then, it is checked whether the sign of the event K to be decoded set in C matches "1" (step G3). If it is "1" (Yes), the node Z
Is set to node Z (step G).
If it is not "1" (that is, if it is "0") from the YES route of step 3 to step G4, the node on the left side of node Z is set to node Z (from the NO route of step G3 to step G5). Further, the lower node determining unit 46
Acquires the node number of the node Z from the node number management unit 42 based on the node number of the node set in the node Z, sends the node number to the leaf / node discriminating unit 47, and At 47, the position information of the node Z having the node number sent is obtained from the node number management unit 42, and it is checked whether this node Z is a node or a leaf (step G6).

If node Z is not a leaf (step G
(NO route of No. 6), the process returns to step G2, and the process is repeated until the event K to be decoded reaches the leaf storing the event K. On the other hand, if the node Z is a leaf (YES route in step G6), it means that the event K to be decoded has been found, so the leaf / node discriminating unit 47 sends the symbol (event) output signal to the node number managing unit 42. The node number management unit 42 that has transmitted and received this signal outputs the event K (symbol) stored in this leaf (step G7) and outputs a decoding processing end signal.

As a result, the “path” represented by the numerical value “1” or “0” of the code tree created on the encoding side is changed to the event K
Can be decoded by tracing to the leaf where is stored. As described above, according to the data restoring apparatus for implementing the data restoring method according to Related Technique 2, a decoded character is registered with a number in a tree-structured context tree, and a code tree corresponding to the context tree is registered. A two-stage process in which a code that matches the code of a character to be decoded is searched from a code table by creating / updating while performing a spraying process, and a character registered corresponding to the matched code is output as a decoded character. Can be performed at the same time, and there is an effect that the speed of the data restoration processing is greatly improved.

Further, similarly to the encoding side, each time a character is input, creation / update of a node of a code tree (spray processing)
Therefore, it is not necessary to perform an enormous calculation process of reconstructing the already constructed probability model every time a character is input, and this has the effect of further improving the speed of the data restoration process. Further, similarly to the encoding side, every time the same code as the code decoded in the past appears, the node of the code tree of the same code registered in the past is recombined with the upper node (spray processing). By reducing the code length to １ ／, as the same code is repeatedly restored, the code can be represented by a smaller number of bits, so that the restoration effect is greatly improved. (B-1) Description of First Modification of Related Technology 2 (1) Description of Encoding Side FIG. 42 shows an internal configuration of a data compression device 3 as a modification of Related Technology 2. As shown in FIG. 42, inside the data compression device 3, in addition to the configuration described above with reference to FIG.
10A, and instead of the encoding unit 104A and the code tree holding unit 105A described above with reference to FIG.
An encoding unit 104A 'and a code tree holding unit 107A are provided.

Therefore, in FIG. 42, description of components having the same reference numerals as those already described in FIG. 33 will be omitted, and only components different from those in FIG. 33 will be described below. That is, the encoding unit 104A 'operates as a code output unit and an escape code output unit, when a symbol is not registered in the code tree, from a node located halfway from the root of the code tree to the leaf where the escape code is stored. When the symbol is registered in the code tree, the escape code is output according to the branch from the node located halfway from the root of the code tree to the leaf of the symbol.

Further, the encoding unit 104A ', as a control means, repeats the processing when encoding the escape code until data encoding is performed. Also, a code tree holding unit (code tree holding means) 107A
Holds an independent code tree for each context in which an escape code (ESC) indicating that a symbol has not been registered is stored in advance. The context discriminating unit (context discriminating unit) 108A includes a code tree determining unit 103 The context change unit (context change means) 110A determines whether or not a symbol is registered in the code tree determined in (1), and reduces the length of the context when no symbol is registered in the code tree. Things.

With a configuration different from that of FIG. 33, in the data compression device 3 shown in FIG. 42, the encoding unit 104A ′ determines that the symbol K is not registered in the code tree from the root of the code tree. The ES according to the branch from the node located halfway to the leaf where the ESC is stored
The code of C is output, and when the symbol K is registered in the code tree, the code of the symbol K is output according to a branch from a node located halfway from the root of the code tree to the leaf of the symbol K.

When the ESC is encoded, the data K
The process is repeated until the encoding of is performed. Further, the code tree holding unit 107A holds an independent code tree for each context in which an escape code (ESC) indicating that a symbol has not been registered is registered in advance.

Hereinafter, the above-mentioned processing will be described in more detail with reference to processing steps H1 to H11 in the flowchart shown in FIG. First, the context change unit 110A
A context character string P ₀ is initialized from all the contexts held in the prefix data holding units 200A-1 to 200A-n (step H1), and this context character string P ₀ is set in the context P (step H1). H2) Then, data (symbol) K to be encoded is input (step H3).

Further, the context changing unit 110A sends the information of the context P and the data K to the context history holding unit 101A and the code tree determining means 103A.
The information of the context P sent from the context change unit 110A is
This is sent to the context determination unit 108A. Then, the context determining unit 108
A determines whether the event K is registered in the context P from the received information on the context P (step H4).

Here, when the event K is registered in the context P, the context history holding unit 101A makes the encoding unit 104
Instruct A 'to encode an escape code (ESC),
The encoding unit 104A 'encodes the escape code by outputting the code corresponding to the branch of the node from the leaf of the escape code (ESC) to the root in the code tree corresponding to the context P (NO in step H4). Step H5 from the route).

Further, encoding section 104A 'instructs code tree updating section 105A to update the code tree through code tree determining section 103A, and code tree updating section 105A
The SC leaf is replaced with another leaf or node (step H6). Then, the order of the context P (the initial state of the code tree is the 0th order) is shifted by one (step H).
7) Returning to step H4, the process is repeated until it is determined that the event K is registered in the context P (Yes).

On the other hand, if the event K is registered in the context P (Yes) in step H4, the context history holding unit 101A instructs the encoding unit 104A 'to encode the event K, The encoding unit 104A 'performs encoding by outputting a code corresponding to the branch of the node from the leaf of the event K to the root in the code tree corresponding to the context P (YES route of step H4 to step H8).

[0234] Then, the encoding unit 104A 'instructs the code tree updating unit 105A to update the code tree through the code tree determining unit 103A. The leaf or the node is rearranged (step H9). Further, the context updating unit 106A rejects the oldest data (the data held in the prefix data holding unit 100-n) and registers the context of the input data K in the prefix data holding unit 100A-1. context switch portion 110A from the updates the context character string P ₀ (step H10).

Then, it is checked whether or not encoding of all data has been completed (step H11). If not completed (NO route of step H11), the process returns to step H2 until all data is encoded. Step H
Steps 2 and subsequent steps are repeated, and if the processing has been completed (YES route in step H11), all the encoding processing is completed.

For details of the code output processing in steps H5 and H8, see the processing steps B1 to B8 described above with reference to FIG. 36. For details, see the processing steps C1 to C9 described in FIG.
Please refer to.

As described above, according to the data compression apparatus according to the first modification of Related Art 2, an escape code (ESC) indicating that no symbol is registered is registered in the code tree in advance, and the encoding is performed. While the symbol is not included in the pre-registered context (until the context in which the symbol is included is found and encoded), the code of this escape code is output, so that the combination of symbols appearing as input data is output. (Context) Since it is not necessary to register all of them in advance, there is an advantage that the memory used for registering the context can be significantly reduced.

As described above, the code length of the escape code to be output while the symbol to be coded is not included in the pre-registered context is shortened (）) by the spraying process. Since it is possible to shorten the time required for finding and encoding a context including a symbol, the processing speed of data compression is greatly improved, and the processing load of the data compression apparatus can be greatly reduced.

(2) Description of Restoration Side FIG. 44 shows the internal structure of the data restoration device 4 as a first modification of the related art 2, and as shown in FIG. In addition to the configuration described above with reference to FIG. 38, a context changing unit 210A is provided inside the device 4, and a decoding unit 204A, a code tree holding unit 205
A decoding unit 204A 'and a code tree holding unit 207A are provided instead of A.

Therefore, in FIG. 44, the description of the components having the same reference numerals as those already described in FIG. 38 will be omitted, and components different from the configuration shown in FIG. 38 will be described below. That is, the code tree holding unit (code tree holding means) 207A
Holds a code tree in which escape codes are registered in advance, and includes a context change unit (context change means) 210
A is for rejecting the input data when the output data is an escape code and shortening the context.

The decoding unit 204A 'scans a node (branch point) from the root (vertex) of the code tree selected by the code tree determination unit 203A according to the code coded on the coding side as a decoding means. Then, the data stored in the leaf that has arrived is output. Furthermore, when the escape code is decoded, the context change unit 210A resets the context as described above and controls the process to repeat the process until data other than the escape code is decoded. It has become.

With the configuration different from the configuration shown in FIG. 38 as described above, in the data restoration apparatus shown in FIG. 44, the code tree holding unit 207A holds the code tree in which the ESC is registered in advance, and the context change unit 210A When the data K output by E. is ESC, the input data K is rejected to shorten the context. Further, the decoding unit 204A ′ scans a node from the root of the code tree selected by the code tree determination unit 203A according to the code of the encoded data K, and outputs data K stored in a leaf reached, When the ESC is decoded, the order of the context is changed by the context changing unit 210A, and the process is repeated until data K other than the ESC is decoded.

Here, the operation as described above will be described with reference to FIG.
This will be described in further detail with reference to processing steps J1 to J9 in the flowchart shown in FIG. First, the context change unit 210
A is preceded by the context string P ₀ from all context held in the data holding unit 200A-1~200A-n is initialized (step J1), and sets this context string P ₀ on the context P (Step J2).

The context changing unit 110A stores the context P in the context history holding unit 201A and the code tree determining unit 203.
A, the code tree determining unit 203A selects (determines) a code tree from the received context P (step J3), and sends the determined code tree to the decoding unit 204A '. Decoding section 204
In A ', the code is decoded by scanning from the root to the leaf in the determined code tree according to the code coded on the coding side (step J4). Note that this decoding unit 204
For details of the processing performed by A ', refer to processing steps G1 to G7 described above with reference to FIG.

Then, decoding section 204A 'checks whether or not the decoded event K is an ESC (escape code) (step J5). If the decoded event K is an ESC, the ESC signal is context-changed. Transmitted to the unit 210A (YES route of step J5). Furthermore, this ESC
Upon receiving the signal, the context change unit 210A changes the order of the context P by one, and changes the order (for example, n-1 ignoring the oldest data held in the prefix data holding unit 200-n). (The next context P is created) (step J6), this context P is sent to the context history holding unit 201 and the code tree determining means 203, and the process returns to step J3.

That is, the decoding section 204A '
The processing from step J2 is repeated until the other event K is decoded. On the other hand, if the decrypted event K is not ESC, the leaf of the decrypted event K is recombined with another leaf or node (NO route from step J5 to step J7). For details of the leaf or node rearrangement processing, see the processing steps C1 to C9 in the flowchart described above with reference to FIG.

Further, the context updating unit 206A rejects the oldest data (the data held in the prefix data holding unit 200-n) and uses the decoded event K as a context and sends it to the prefix data holding unit 200-1. Insert and register the context string P
₀ is updated (step J8). Then, it is checked whether or not decoding has been completed for all data (step J).
9) If not completed, the processing from step J2 is repeated (from the NO route of step J9 to step J2).
2) If not, the decryption process ends (step J).
9 YES route).

In this case, as in the case of the encoding side, either of the above-described processing of changing the node (step J7) and updating of the context (step J8) may be performed first.
Processing may be performed in parallel. Thus, the first of the related technologies 2
According to the data restoration device of the modified example, an escape code (ESC) indicating that a symbol is not registered
Is registered in the code tree in advance, and if the decoded symbol is this escape code, the context is shortened (changed) until the code other than the escape code (that is, the code of the symbol to be decoded) is decoded. By searching for the code of the symbol to be used, all combinations (contexts) of symbols appearing as input data do not need to be registered in the code tree in advance. is there.

While the symbol decoded as described above is an escape code, the code length of the escape code is shortened (1/2) by spray processing to find a context containing the symbol to be decoded. Since the time until the decoding is performed can be shortened, the speed of the data restoration process is greatly improved, and the processing load of the data restoration device can be greatly reduced. (B-2) Description of Second Modification of Related Technology 2 (1) Description of Encoding Side FIG. 46 shows an example of the internal configuration of a data compression device 3 as a second modification of Related Technology 2. FIG. 46
As shown in FIG. 38, a code registration unit 112A is provided inside the data compression device 3 in addition to the configuration described above with reference to FIG. 38 in the description of the first modification of the related technique 2.

Therefore, in FIG. 42, the description of the components having the same reference numerals as those already described in FIG. 33 will be omitted. Also,
The code registration unit 112A registers the data K in the code tree when the input data K is not registered in the code tree. With such a configuration, when the input data K is not registered in the code tree, the code registration unit 112A can register the data K in the code tree.

Here, the operation as described above will be described with reference to FIG.
The processing will be described with reference to processing steps K1 to K12 of FIG. 7, but here, as shown in FIG. 47, the processing other than step K8 is the same as the processing steps H1 to H11 described above in the flowchart of FIG. It is. That is,
In this example, in steps K1 to K7, the same processing as steps H1 to H7 in FIG. 43 is performed, and thereafter, processing related to step K8 is performed.

That is, when the context discriminating unit 108A determines that the event K is not registered in the context tree (NO route in step K4), the code tree updating unit 105A replaces the ESC leaf of the code tree with another leaf. Alternatively, the sign of the ESC is changed in combination with the node (step K6), and the context history holding unit 101A stores the current context P in the code registration unit 112A.
And the context change unit 110A changes the order of the context P by one (step K7), and then changes the order of the context P.
2A registers event K in the code tree (step K8).

Even if it is determined in step K4 that event K is registered in the context tree, the same processing as steps H8 to H11 in FIG. 43 is performed in steps K9 to K12. I have. As described above, according to the data compression device according to the second modification of the related technique 2, as described above, except for step K8,
Since this is the same as the processing step in FIG. 43 on the encoding side of the first modification of Related Art 2, it has the same effect as the encoding side of the first modification of Related Art 2.

Further, as described above, by taking step 8, symbols during which escape codes are encoded are registered in the code tree, and symbols which have not been registered in the code tree in advance are also subjected to the next code. Since the encoding can be performed at an early stage (higher order), the compression effect is greatly improved as the encoding proceeds. (2) Description of Restoration Side FIG. 48 shows an example of the internal configuration of the data restoration device 4 as a second modification of the related art 2, and FIG.
As shown in FIG. 44, a code registration unit 212A is further provided inside the data restoration apparatus 4 in addition to the configuration described above with reference to FIG. 44 in the description of the restoration side of the first modification of the related technique 2. ing. The code registration section 212A is provided corresponding to the configuration on the coding side (see FIG. 46).

Therefore, in FIG. 48, the description of the components having the same reference numerals as those already described in FIG. 44 will be omitted. The code registration unit 212A registers the code of the decoded data in all the code trees corresponding to the context when decoding the ESC (escape code) in the decoding process of the data encoded on the compression side. is there.

Accordingly, in addition to the operation of the configuration described above with reference to FIG. 44, when the code registration unit 212A decodes the ESC in the decoding process of the encoded data K, all the codes corresponding to the context are output. The code of the decoded data K can be registered in the code tree. The above operation will be described in further detail with reference to processing steps L1 to L10 in FIG.

Here, as shown in FIG. 49, processing steps L1 to L4 are the same as processing steps J1 to J4 described above with reference to FIG. 45 on the restoration side of the first modification of the related technique 2. Processing is performed. Then, after the decoding unit 204A decodes the code in Step L4, the code tree updating unit 205A rearranges the leaf of the decoded event K with another leaf or node (Step L5).

At this point, if the ESC (escape code) has been decoded before and the ESC signal from decoding section 204A has been received at this time, all The event K is registered in the code tree (step L6). Furthermore, the decrypted event K is ES
C (step L7), and the decrypted event K
Is an ESC, the ESC signal indicating that the decoded event K is the ESC is transmitted to the context change unit 210A and the code registration unit 212A, and the context change unit 210A that has received the ESC signal The order is shifted to one lower order and changed (from the YES route of step L7 to step L
8) The process returns to step L3 to repeat the process until the event K other than ESC is decoded.

When the event K decoded by the decoding unit 204A is ESC, the code registration unit 212A creates a new leaf in the code tree, and the decoding unit 204
When the event K other than the above is decoded, the symbol can be registered in all the code trees in which the ESC is restored by storing the event K in all the newly created leaves.

On the other hand, if the decrypted event K is not ESC in step L7, the context updating unit 206A rejects the oldest data (data held in the prefix data holding unit 200-n), the decoded event K registers inserted into the pre-data retaining unit 200-1 as a context, to update the context character string P ₀ (step L9). Then, it is checked whether decoding has been completed for all data (step L10). If not completed, the processing from step L2 is repeated (NO route of step L10), and if completed, the decoding processing is ended (step L10). YES at step L10
root).

As described above, on the decoding side, similarly to the encoding side, when the decoding unit 204A decodes the ESC, the code tree registration unit 212A newly registers the event K in the code tree. As described above, according to the data decompression device according to the second modification of the related art 2, in addition to the effects described above on the decompression side in the first modification, the escape code By decoding the symbols of the symbols to be decoded in the code tree during the decoding of symbols, symbols that are not registered in the code tree can be decoded at an early stage in the next decoding. As the data decoding process proceeds, the effect of restoring is greatly improved and the processing load on the data restoring device can be greatly reduced. (B-3) Description of Third Modified Example of Related Technology 2 (1) Description of Encoding Side In the third modified example, the above-described data compression device 3
Compared with the second modification, when encoding the data K, if the ESC has been encoded at least once, the context change unit 110A as the history registration unit sets the context immediately before the encoding of the data. Is registered in the context history holding unit 101A, and the code registration unit 112A newly registers data in a code tree having an escape code encoded immediately before encoding the data. Is different.

Hereinafter, the above-described processing will be described in more detail with reference to processing steps M1 to M13 shown in FIG. Here, as shown in FIG. 50, step M1
In steps M1 to M9, the same processes as those in the processing steps H1 to H9 in FIG. 43 are performed.

If the event K of the input data is registered in the context P (YES route in step M4),
After the code tree is rearranged in step M9 via step M8, the decoding unit 104 checks whether the event K encoded in step M8 is an ESC (step M10). If the encoded event K is ESC, the code registration unit 112A registers the event K in the code tree corresponding to the context P 'immediately before encoding the event K (from the YES route of step M10 to step M11). The context updating unit 106A registers the context P including the event K in the prefix data holding unit 100A-1 as the newest context.

Further, from this information, the context change unit 110A
But updated by inserting the data K in the context string P ₀ (step M12), and registers the context history retaining unit 101A. That is, since the data K is registered in the code tree of the context P ′ immediately before encoding the data K in step M11 (that is, the context encoded last), the data K and the data K immediately before encoding the data K are registered. Is registered in the context history holding unit 101A by the context changing unit 106A.

On the other hand, if the encoded event K is not ESC (NO route of step M10), step M11
Is skipped, and the above-described step M12 is performed. Further, it is checked whether or not encoding of all data has been completed (step M13). If not completed (NO route of step M13), the process returns to step M2, and encoding of all data is completed. The process is repeated until the encoding process is completed (YES route of step M13).

As described above, according to the data compression apparatus according to the third modification of the related art 2, in addition to the effects described above on the encoding side of the second modification, the symbol is added to the context registered in advance. Is not included, by registering this symbol only in the code tree of the last encoded escape code, the amount of memory used to register a new context can be significantly reduced. This has the effect of significantly improving the performance of the data compression device.

Further, each time the same symbol as the symbol newly registered as described above is inputted later, the node of the code tree of this symbol is rearranged to shorten the code length (spray processing). Since the code length of the code can be shortened only for a symbol having a high frequency of appearance, the compression effect of the data compression device is greatly improved.

(2) Description on the Restoration Side Data restoration device 4 according to the third modification of Related Art 2
Is different from the data restoring apparatus 4 shown in FIG. 48 in that the context change unit 210A as the history registration unit finally converts the ESC (escape code) in the decoding process of the data K encoded on the encoding side. The context at the time of decoding and the decoded data K are registered in the context history holding unit 201A, and the code registration unit 212
A is different in that A can register the code of the data K in a code tree corresponding to the context when the ESC was decoded last in the decoding process of the data K.

The above processing will be described in further detail with reference to processing steps N1 to N10 in FIG. Here, as shown in FIG.
In N5, the same processing as in steps K1 to K5 in FIG. 49 is performed.

Then, on the restoration side, after recombining the leaf of the event K decoded in step N5 with another leaf or node, it is checked whether the decoded event K is an ESC (step N6). If the decoded event K is an ESC, the order of the context P is changed (Y in step N6).
From the ES route, step N7), the process returns to step N3, and repeats the process until the event K other than ESC is decoded.

On the other hand, if the decoded event K is not an ESC, the code tree updating unit 205A creates a new leaf only in the code tree obtained by decoding the immediately preceding ESC, and sets the code registration unit 212A
Registers the event K in the new leaf of this code tree (from the NO route of step N6 to step N8). Further, the context updating unit 206A rejects the oldest data (data held in the prefix data holding unit 200-n) and inserts the decrypted event K into the prefix data holding unit 200-1 as a context. And updates the context character string P ₀ (step N
9).

Then, it is checked whether or not decoding has been completed for all data (step N10). If not completed, the processing from step N2 is repeated (NO route from step N10 to step N2), and the processing must be completed. If so, the decoding process ends. As described above, according to the data restoration device according to the third modification of Related Art 2, in addition to the effects described above on the restoration side of the second modification, no symbol is included in the pre-registered context. In this case, the code of this symbol is newly registered only in the code tree of the escape code decoded last, so that one or less registration is always required for one symbol, and the code of the new symbol is registered. For this reason, the memory for node ID management used for this purpose can be greatly reduced, so that there is an effect that the performance of the data restoration device is greatly improved.

Further, each time the same symbol as the symbol newly registered as described above is inputted later, the node of the code tree of this symbol is rearranged to shorten the code length (spray processing). Only a symbol having a high frequency of occurrence actually has a code with a short code length, so that there is an effect that the restoration effect of the data restoration device is greatly improved. (C) Description of an Embodiment of the Present Invention A data compression apparatus and a data decompression apparatus according to an embodiment of the present invention also include a data compression method and a data compression method of the present invention as shown in FIG. This is for implementing the restoration method.

Also in this embodiment, the related art 2
In the same manner as described above, the description will proceed with the data compression device as the encoding side and the data decompression device as the decompression side. Note that also in the following description, the context tree and the code tree have the configuration described in Related Art 1. (1) Description on the Encoding Side FIG. 52 is a diagram showing an example of the internal configuration of a data compression device 3 (see FIG. 32) for implementing a data compression method according to an embodiment of the present invention. At 52, 30
1B is a code tree holding unit, 302B is a context tree holding unit, 303
B is a context registration unit, 305B is a context change unit, 306B is an encoding unit, 307B is a sign change unit, 321B is a context holding unit, and 322B is a code registration unit.

Here, the code tree holding section (code tree holding means)
301B holds a code tree in which an escape code (ESC) (data indicating data not registered) is registered in advance, and a context tree holding unit (context tree holding unit) 302B
It stores a context tree in which a combination of a symbol K (input data) and a context is registered. The context registration unit (context registration unit) 303B newly registers the symbol K in the context tree after encoding the escape code. The context holding unit 321B stores the input symbol K
Is once held.

The code registration unit (code registration means) 322B
After encoding the escape code, the symbol K is newly registered by branching the escape code leaf (data storage point) of the code tree in the code tree holding unit (code tree holding unit) 301B. Therefore, the code registration unit 322B includes a new node ID generation unit 61, which will be described later with reference to FIG.
A latch 62 and a parent-child information updating unit 63 are provided, and inside the code tree holding unit 301B, external nodes (leaf I
D) Holder 64, Internal Node (Node ID) Holder 65,
An ESC-ID holding unit 66 and a code tree management unit 67 are provided.

The context changing unit 305B outputs the symbol K
When the combination of and is not held in the context tree, the context is changed. The encoding unit 306B
It outputs a code represented by "1" or "0" according to the branch from the top of the code tree to the symbol K or the leaf in which the escape code is registered.

The code updating unit 307B replaces a leaf in which the encoded symbol K and escape code are registered with another leaf or node. Then, as shown in FIG. 53, inside the code registration unit 322B, the new node ID generation unit 61
02B, the two new node IDs (I
D-1 and ID-2 are generated, and the latch 62 temporarily holds an escape code ID (ESC-ID).

The parent-child information updating section 63 has three pieces of information (ESC-ID) of the upper node ID of the node to be processed, the node ID of the lower node located at the lower right, and the node ID of the lower node located at the lower left. , ID-1, ID-
Receiving the parent-child information consisting of 2), changing this parent-child information,
This is sent to the code tree holding unit 301B. Further, inside the code tree holding unit 301B, external nodes (leaf I
D) The holding unit 64 holds the leaf ID of the leaf that is the storage point of the code tree data, and the internal node (node ID) holding unit 65 holds the node ID of the node of the code tree. The ESC-ID holding unit 66 holds the escape code of the code tree and the ID of this escape code.

Further, the code tree management section 67 receives the context ID from the context tree holding section 302B, and stores the context ID in the external node (leaf ID) holding section 64 and the internal node (node ID).
This is sent to the holding unit 65 and the ESC-ID holding unit 66. With the above-described configuration, in the data compression device 3 according to the embodiment of the present invention, the code tree holding unit 301B holds a code tree in which an escape code is registered in advance, and the context tree holding unit 302B stores the symbol K and the context P After holding the context tree in which the combination is registered and the context registration unit 303B encodes the escape code, it is possible to newly register the symbol K in the context tree.

Furthermore, after the context holding unit 321B once holds the context P, and the code registration unit 322B encodes the escape code, the symbol K is newly registered by branching the escape code leaf of the code tree. it can. Further, when the combination of the input symbol K and the context P is not stored in the context tree,
The context P can be changed.

Further, the encoding unit 306B outputs a code according to the input data from the top of the code tree or the branch to the leaf where the escape code is registered, and the encoded data and the escape code are registered by the code update unit 307B. One leaf can be replaced with another leaf or node. FIG. 57 (a) is a diagram showing an example of a code tree, and FIG. 57 (b) is a diagram showing an example of a context tree. By the way, as shown in FIG. 57 (a), the code tree has ID numbers (0 to 10) in the root and the node as the internal nodes and in the leaves as the external nodes, respectively.

On the other hand, as shown in FIG. 57 (b), the context tree has a context ID and an ID number of a symbol registered in the context, and the context ID number is the ID of the root of the code tree. The ID numbers of the numbers and symbols are the same as the ID numbers of the leaves of the code tree. Here, regarding the above operation,
This will be described in further detail with reference to processing steps P1 to P16 showing the operation on the encoding side of the present invention shown in FIGS.

In the following description of the operation, it is assumed that the code tree and the context tree have the above-described configuration.
First, as shown in FIG. 54, when the symbol K is input (step P1), the context P stored in the context storage unit 321B is output to the context change unit 305B (step P2).

Then, the context change unit 305B outputs the context P
And the symbol K, it is determined whether the symbol K is registered in the context P. If the symbol K is not registered in the context P, the context tree holding unit 302B transmits the context change signal to the context change unit. 305B (step P
3). Upon receiving the context change signal, the context change unit 305B rejects the highest-order character (the leaf that is the longest distance from the root of the context tree) and reduces the context P by one to the context tree holding unit 3
02B (Step P4).

This process is repeated until the context P in which the symbol K is registered is determined. Next, FIG.
, The context holding unit 302B stores the ID of the context P
(No.) and the ID of the symbol K (ESC when the symbol K is not registered) is sent to the encoding unit 306B (step P5), and the encoding unit 306B sends the transmitted ID to the code tree holding unit 301B. Transfer as it is (Step P
6).

The code tree holding unit 301B stores the ID number of the upper node of the transmitted ID and the coding unit 306.
Information indicating whether the ID sent by B is located on the right or left of the upper node is sent to encoding section 306B (step P7). Further, the encoding unit 306B
I sent from the encoding unit 306B to the upper node
According to the position information of the node having D, for example, "1" is output as a code if it is located on the right, and "0" is output as a code if it is on the left (step P8).

When the ID of the upper node sent together with the above-mentioned position information matches the ID (root ID) of the context P sent from the context holding unit 302B, the encoding process ends. On the other hand, when they do not match, the ID of the context P is further output to the sign changing unit 307B (the same path as in step P6), and the code tree holding unit 30
The upper node ID and position information are obtained from 1B.

The processing is repeated until the ID number of the upper node from the code tree holding unit 301B matches the ID of the context P. After this processing is completed, the sign changing unit 307
B receives the ID of the context P (= root ID of the code tree) and the leaf ID of the coded symbol K from the coding unit 306B (step P9), performs a node rearrangement process (spray process), and sets the code length. Update. Note that this node rearrangement process is performed as described above in Related Techniques 1 and 2.

Thus, if the symbol K is previously input and registered in the context P, and the symbol K is further input, the already registered node of the symbol K is rearranged with the upper node, and The length can be shortened (１ ／). By the way, in the context P described above, the symbol K
Is not registered, the context registration unit 310B receives the context P to be registered from the context change unit 305B (step P10) and the symbol K (step P11), as shown in FIG. The ID of the registered symbol is output to the holding unit 302B (step P12), and the context tree holding unit 302B newly registers the symbol K under the context P.

On the other hand, code registration section 322B receives a code tree for registering a code from code tree holding section 301B (step P13), and stores symbol K to be registered and context tree holding section 302
B in response to the ID of the registered symbol (step P1
4, 15), the symbol K is newly registered in the code tree and stored again in the code tree holding unit 301B (step P16). As a result, registration (encoding) of the symbol K not registered in the context P is performed.

[0292] Here, the code registration section 322B encodes the escape code, and then branches the escape code leaf of the code tree in the code tree holding section 301B to obtain the symbol K
For newly registering (the above-described steps P13 to P1)
As described above, 6) will be described in more detail with reference to FIG. First, the code tree management unit 67 provided inside the code tree holding unit 301B receives the context ID and sends the ESC address of the context to the ESC-ID holding unit in the code tree holding unit.

Then, the ESC-ID holding unit 66 stores the ES
While receiving the C address, it outputs the ID of the ESC and the symbol registered in this ID (ESC in this case),
In the code registration unit 322B, the ESC-ID and the ESC are latched by the latch 62. Further, the new ID generator 61
Upon receiving the update signal, two ID numbers (ID-1, ID-
2), and the ID-1 is stored in the code tree holding unit 301B together with the ESC latched as the new ESC-ID.
Is stored in the ESC-ID holding unit 66.

[0294] In addition to the ID and the symbol, the code tree holds parent-child information indicating the position information of the ID.
This parent-child information includes three pieces of information: a node ID of a higher order of the user, a node ID located at the lower right of the user, and a node ID located at the lower left of the user. The parent-child information updating unit 63
Three IDs (ESC-ID before change, ID-1, ID-
In response to 2), the parent / child information is changed. That is, ID-
ESC-ID is registered in the upper ID of 1, ID-2,
Also, ID-1 is at the lower right of the ESC-ID, and ID- is at the lower left.
The information that 2 is located is registered.

The parent / child information is held in the node ID holding unit 65 of the code tree holding unit 301B together with each ID. on the other hand,
The registered symbol and the new ID (ID-2) are registered in the leaf ID holding unit 64 of the code tree holding unit 301B. By performing the above processing, the new ES
The C-ID (ID-1) is registered, the old ESC-ID is held as a node ID in the node ID holding unit together with the parent-child information, and the new ID (ID-2) and the symbol K are stored as new leaves in the leaf ID holding unit. The process of branching the leaf, in which the escape code is stored in the code tree holding unit 301B in which the escape code of the code tree is registered, and newly registering the symbol K, ends.

The operations described in FIGS. 53 to 56 can be summarized as a flowchart shown in FIG. That is, first, the context P ₀ is initialized by inputting 0 (step Q1), and the context P ₀ is input to the context P as a variable (step Q2). Note that the context P ₀ is a character (symbol) input and encoded up to immediately before,
For example, when the encoding in the present embodiment is a model using an n-th order context, the context P ₀ is input / output immediately before.
The encoded (n-1) characters are stored.

Then, when the symbol K is input, it is searched whether or not the symbol K is registered in the context tree of the context P (step Q3). If the symbol K is not registered in the context tree of the context P, the code of the ESC (escape code) is output (from the NO route of step Q3 to step Q4), and the ESC of the code tree corresponding to the context P is registered. Spray processing is performed on the leaves (step Q
5).

Then, the leaf of the above ESC is branched (step Q6), and the ESC and the symbol K are registered in the two new leaves thus obtained (step Q7), and the context P
The symbol K is also registered in the context tree. Further, after the symbol K is newly registered as described above, the oldest character in the context P is rejected, and the context P with the degree of the context reduced by 1 is newly changed to the context P (step Q).
8).

Then, returning to step Q3, the symbol K
Until the context P is detected as being registered in the context P.
Are sequentially changed and the process is repeated. On the other hand, when the symbol K is registered in the context tree of the context P, the code of the symbol K is output (from the YES route of step Q3 to step Q3).
9) The leaf in which the symbol K of the code tree corresponding to the context P is registered is subjected to spray processing (step Q10).

Further, after encoding the symbol K, the context P ₀
Updating the context P ₀ and additionally registers the symbol K (Step Q11). (E.g. by adding the symbol K in the context P _0, rejects the oldest character in the context P _0). And
It is checked whether encoding of all characters (symbols) is completed (step Q12). If encoding is not completed (NO route of step Q12), the process returns to step Q2, and encoding of all characters is performed. The process is repeated until the process ends.

In the processing in FIG. 58 described above, the spray processing of the ESC leaf is performed after the ESC and the symbol K are registered. However, the processing order may be reversed. In this case, the processing steps are as follows. As shown in FIG. Here, as shown in FIG. 59, in steps R1 to R3 and steps R9 to R12, processing similar to processing steps Q1 to Q3 and steps Q9 to Q12 in FIG. 58 is performed, respectively.

If the symbol K is not registered in the context P at step R3, the code of the ESC is output (step R4), the leaf of the ESC is branched (step R5), and the ESC and the symbol K are added to the new leaf. Is registered (step R6). Then, after the registration is performed as described above, the spray processing is performed on the leaves of the ESC (step R7).

Further, similarly to the processing step Q8 in FIG. 58, the context P is changed (step R12), and the process proceeds to step R3.
Is repeated until symbol K is detected. For example,
When the code tree is in a state where characters (symbols) A to E are already encoded and registered as shown in FIG. 60A, the above-described processing steps R1 to R12 (or the processing in FIG. 58) In steps Q1 to Q12), when the processing is executed with the symbol K as the character F, the leaf of the ESC having the leaf number 6 is branched, and as shown in FIG. ESC and letter F are registered in the leaves, respectively.

For example, if the context used in the above processing is a tertiary context, the symbol K becomes the 0th order (initial state).
Are registered in the primary, secondary, and tertiary contexts, respectively (hereinafter, a method of performing registration in all the orders is referred to as a full registration type). 58 and 59.
Steps Q1 to Q12 and Steps R1 to R
Reference numeral 12 denotes a step of processing for registering the symbol K in the contexts of all orders every time the ESC is encoded, as described above, but the order encoded (registered) immediately before the symbol K is encoded. The processing may be performed so that the symbol K is registered only in one of the contexts. A flowchart of the processing in this case is as shown in FIG.

That is, in the processing shown in FIG. 61, first,
Context P ₀ is initialized to 0 (step T1), context P ₀ is input to context (variable) P, and ₀ is input to context (variable) X (step T2). Further, it is searched whether the symbol K is registered in the context P (step T3).
If the symbol K is not registered in step S4, the same processing as in steps Q4 and Q5 (see FIG. 58) is performed (steps T4 and T5 from the NO route in step T3).

Thereafter, the context P is input to the context X (step T6), and the context P is changed (step T7).
The process is repeated until it is detected that the symbol K is registered in. On the other hand, when the symbol K is registered in the context P in the above-described step T3, if the above-described steps Q9 to Q11 (see FIG. 58) or steps R9 to
The same processing as R11 (see FIG. 59) is performed (steps T8 to T10).

After that, the leaf of the ESC of the context X is branched (step T11), and the ESC and the symbol K are registered in the two new leaves thus branched (step T12). Further, it is checked whether or not encoding of all characters (symbols) has been completed (step T13). If not completed, the processing from step T2 is repeated (NO route of step T13). The encoding process ends (YES route 9 in step T13).

By performing the processing as described above, instead of registering the symbol K in the context P of all orders,
Registration can be performed only in the context of the order immediately before encoding the symbol K (context X) (hereinafter, a method of registering a symbol only in the context of the immediately preceding order is referred to as a sequential registration type). As described above, according to the data compression apparatus according to the embodiment of the present invention, when the symbol K is not registered in the context P, the code length of the branch / registration of the escape code (ESC) is set to ( Code length +1) bits,
By setting the code lengths of newly registered codes and escape codes to a minimum of 2 bits, if the data is such that relatively many escape codes are output, or dictionary registration (registration of symbols in the code tree) is not sufficient. There is an effect that a high coding rate can be obtained in an initial stage or the like.

If the spray processing is performed before the new registration of the symbol as described above, the code length of the code and the escape code is at least 2 bits. If the spray processing is performed after the new registration, the code of the escape code is minimized. Thus, the coding efficiency can be greatly improved. Further, in the case of the above-described sequential registration type, new registration of a symbol in the code tree is always performed one by one, and secondary and tertiary registration is performed when the same symbol appears twice and three times. Only symbols with reproducibility are always registered in the higher order of the code tree, and the coding efficiency of the code tree caused by the presence of symbols that have been registered in the code tree but are not actually used. Also, there is an effect that the encoding efficiency after the dictionary is sufficiently registered is greatly improved.

[0310] The sequential registration type also has the advantage of using less memory capacity (dictionary capacity) than the full registration type. (2) Description of Restoration Side FIG. 62 is a diagram showing an example of the internal configuration of the data restoration device 4 (see FIG. 32) for performing the data restoration method according to an embodiment of the present invention. At 40
1B is a code tree holding unit, 402B is a context tree holding unit, 403
B is a context change unit, 404B is a decoding unit, 407B is a code registration unit, 408B is a context registration unit, 409B is a latch, 42
1B is a context holding unit.

Here, the code tree holding unit (code tree holding means)
401B holds a code tree in which an escape code (ESC) (data indicating data not registered) is registered in advance, and a context tree holding unit (context tree holding unit) 402B
It holds a context tree in which a combination of a decoded symbol (data) and a context is registered. The context change unit 403B searches the context tree stored in the context tree storage unit 402B, and changes the context if the reached leaf is an escape code.
When the symbol K encoded on the encoding side is input, the code tree holding unit 40
The code of the symbol K is decoded by scanning from the root (vertex) of the code tree held in 1B to the leaf (data storage point).

[0312] Further, the code changing section 406B recombines the leaf of the decoded symbol K and the escape code with another leaf or a node as a branch point. The code registration unit (code registration means) 407B also has a function as a code tree determination means, and converts a symbol decoded immediately before decoding the symbol K into a symbol K
Is determined in the code tree holding unit 401B in which the code is registered, and when the escape code is decoded, the leaf of the escape code registered in this code tree is branched to newly create a leaf, The decoded symbol K is newly registered in this leaf.

For this reason, the code registration section 407B and the above-described code tree holding section 401 provide a code registration section 322B and a code tree holding section 301B (FIG. 52) on the encoding side, respectively.
(See FIG. 53). Further, the context registration unit 408B includes a code registration unit 407
The symbol K registered in B is registered in the context tree held in the context tree holding unit 402B.
B temporarily holds the symbol K decoded by the decoding unit 404B, and the context holding unit 421B holds the decoded symbol K.

Further, the above-described code tree holding unit 401B can hold a code tree in which an escape code has been registered in advance, and the context tree holding unit 402B can store a combination of the decoded symbol K and the context P in a context. It can hold trees. Further, the context change unit 403
B, when the reached leaf is an escape code, the context can be changed, and the decoding unit 404B scans from the root of the code tree to the leaf according to the code of the encoded symbol K, and The code can be decoded.

The code changing section 406 also serving as a code tree determining means can determine the code tree holding the code of the symbol K from the symbols decoded up to immediately before. Leafs can be recombined with other leaves or nodes. Further, when the escape code is decoded by the code registration unit 407B, the leaf of the escape code can be branched to newly create a leaf, and the decoded symbol K can be newly registered in this leaf.

The context registration unit 408B stores the symbol K registered by the code registration unit 407B in the context tree holding unit 40.
2B, the symbol K decoded by the decoding unit 204B can be temporarily stored by the latch 409B, and the context change holding unit 421 can store the symbol K.
The symbol K decoded in 04B can be held.

The above-mentioned operation will be described in further detail with reference to processing steps U1 to U14 showing the operation on the restoration side shown in FIGS. 63 and 64, similarly to the description on the encoding side. First, as shown in FIG.
21B holds the symbol (context) decoded so far and outputs it to the context change unit 403B (step U1), and the context change unit 403B outputs the initially sent context to the context tree holding unit 402B as it is. (Step U2).

The context tree holding unit 402 outputs the context ID sent from the context changing unit 403B, that is, the root ID, to the decoding unit 404B (step U3). Here, in the decoding unit 404B, if the code (1 bit) for the transmitted route ID is “1”, for example,
If "0", the node (or leaf) located at the lower left
ID is requested from the code tree holding unit 401B (step U
4).

[0319] The code tree holding unit 401B also stores the node ID of the requested node (or leaf) in the decoding unit 40B.
4B is returned (step U5). Then, the decoding unit 40
The 4B and code tree holding unit 401B repeats the above processing until the leaf ID of the leaf at the end of the code tree is obtained.
That is, the decoding unit 404B follows the code tree of the code tree holding unit 401B according to the code coded on the coding side until reaching the leaf where the symbol K to be decoded is registered.

When the target leaf is found, the decoding unit 404B decodes this leaf and sets the sign change unit 40
6B updates the code length by performing spray processing on the decoded leaf in the same manner as the encoding side. Here, if the symbol decoded in this process is ESC, the decoding unit 4
04B sends this symbol (ESC) to the latch (step U6), and the latch once holds this symbol,
This is sent to the context changing unit 403B (step U7). Context change section 403B performs the same context change processing as that on the encoding side, and performs decoding again.

When the symbol decoded by the decoding unit 404B in the above processing is other than ESC, that is, the symbol K, as shown in FIG.
The decoded symbol K is sent to the context registration unit 408B via the latch 409B and the context holding unit 421B (steps U8 to U11), and the context registration unit 408B newly registers the symbol K in the context tree holding unit 402B.

The code registration unit 407B receives the root ID of the context P in which the symbol K has been registered from the context tree holding unit 407B (step U12), and sends this root ID to the code tree holding unit 401B (step U13). ). In the code tree holding unit 401B, the route ID of the sent context P
The code registration unit 407B returns the root ID of the code tree having the same root ID to the code registration unit 407B (step U14), and the code registration unit 407B registers the new code of the symbol K in the code tree having the root ID (step U14). U13).

The above-mentioned code registering section 407B on the restoration side
The process of registering the symbol K in the code tree holding unit 401B is the same as the process of registering the symbol K in the code tree holding unit 301B by the code registering unit 322B on the encoding side.
For this reason, if the registration process on the encoding side is of the all-registration type as shown in FIGS. 58 and 59 in the description of the encoding side, on the decompression side, all registrations in all contexts in which the ESC is decoded are also performed. It becomes a registration type, and in the case of a sequential registration type as shown in FIG.
This is a sequential registration type in which the symbol K is registered in the context of the SC.

Then, similarly to the description on the encoding side, the processing on the restoration side described above can be represented by a flowchart as shown in FIG. That is, a numerical value of the maximum order is input to the context (variable) P ₀ to initialize it (step V1), and this context P ₀ is input to the context P (step V2). That is, when decoding a code, first, processing is performed using the context of the maximum order.

Then, in the code tree corresponding to the context P of the maximum degree, the code registered in the leaf is decoded (step V3). Further, it is checked whether the decoded code is a symbol (step V4). If the decoded code is not a symbol, that is, if it is an ESC, the leaf of the decoded ESC is spray-processed similarly to the encoding side. (From the NO route of step V4 to step V
5) Reject the highest-order symbol (oldest symbol) in the context P, shift the context to one lower order and change it (step V6), and return to step 2. That is, until the symbol other than the ESC (symbol K) is decoded, the context P is changed to the context obtained by subtracting one from the highest order, and the context P in which the symbol K is registered is searched.

On the other hand, if the decoded code is a symbol, it means that the symbol K has been decoded, so that the symbol K is output (from the YES route of step V4 to step V7), and the symbol K leaf is encoded. The code length of the symbol K is shortened (updated) by performing spray processing in the same manner as the conversion side (step V8). Furthermore, additionally registers the symbol K in the context P ₀ (step V9), ESC is rejected. The change of the context P ₀ is performed in the same manner as that on the encoding side.

Further, for the decoded symbol K, if the registration method of the symbol K on the encoding side is the all-registration type, the leaf of the ESC is branched by the all-registration type, and the new symbol K is newly registered. The symbol K is registered (step V10). Then, it is checked whether the decoding of all the input codes has been completed (step V11). If the decoding has not been completed (NO route of step V11), the process returns to step V2, and the decoding of all the codes has been completed. Repeat the process until

As described above, according to the data restoration apparatus according to one embodiment of the present invention, similarly to the coding side, in the new symbol registration processing, the leaf already existing on the code tree is divided into two. By setting the code length of this leaf to (the code length of the leaf before division + 1) bits, the code length of the newly registered symbol K and the code length of the escape code can be reduced to at least 2 bits. If the data is such that the code is decoded relatively much,
Alternatively, in an initial stage where dictionary registration (registering of symbols in the code tree) is not sufficient, there is an effect that data decoding efficiency is greatly improved.

If the spray processing is performed before the new registration of the symbol as described above, the code length of the decoded symbol and the escape code is at least 2 bits. If the spray processing is performed after the new registration, the escape code is obtained. Can be reduced to one bit at a minimum, so that the decoding efficiency of data is further improved. Further, as described above, there is an advantage that the code can be accurately decoded by performing the same registration processing on the restoration side as on the encoding side. (C-1) Description of First Modification of this Embodiment In a data compression device and a data decompression device according to a first modification of this embodiment, as in the above embodiment,
This is for implementing the data compression method and the data decompression method shown in FIG.

Also, as in the above-described embodiment, the data compression device 3 will be described below on the encoding side, and the data decompression device 4 will be described on the decompression side. (1) Description on Encoding Side The configuration on the encoding side is the same as the configuration described above with reference to FIG.

The code registering unit 322B shown in FIG. 52 of this embodiment stores symbols in the leaf of the longest code length on the code tree held by the code tree holding means 301B as shown in FIG. As shown in FIG.
A D generating unit 61, a latch 62, a parent-child information updating unit 63, and a longest code detecting unit (branch position searching means) 69 are provided. Correspondingly, an internal node (node ID) is stored in the code tree holding unit 301B. ) A holding unit 65, a code tree management unit 67, and an external node / ESC-ID (leaf ID) holding unit 68 are provided.

Here, inside the code registration unit 322B, the new node ID generation unit 61
B receives the update signal and receives two new node IDs (ID-
1, ID-2), and the latch 62
This latches the leaf ID detected by the longest code detection unit 69. The parent-child information updating unit 63 also has three pieces of information (ESC-ID, ID-ID) of the upper node ID of the processing target node, the node ID of the lower node located at the lower right, and the node ID of the lower node located at the lower left. 1, ID-2)
In response to the parent-child information consisting of, the parent-child information is changed and sent to the code tree holding unit 301B.

Longest code detecting section (branch position searching means) 69
Obtains the node ID of the code tree from the code tree holding unit 301B and obtains the ID of the leaf having the longest code length in the code tree.
(ID-0) is detected. Further, inside the code tree holding unit 301B, the internal node (node ID) holding unit 65 holds the node ID of the code tree, and the external node / ESC-ID (leaf ID) holding unit 68
Holds the leaf ID of the code tree.

The code tree management unit 67 includes a context tree holding unit 302
B, the context ID is stored in the internal node (node ID) holding unit 65 and the external node / ESC-I.
This is sent to the D (leaf ID) holding unit 68. Since the code registration unit 322B and the code tree holding unit 301B have the above-described configuration, the code registration unit 322B searches for the leaf having the longest code length on the code tree held in the code tree holding unit 301B, and escapes. After encoding the code, the leaf having the longest code length searched is branched and a symbol K is newly registered.

Further, the above-mentioned processing will be described in detail with reference to processing steps W1 to W13 in the flowchart shown in FIG. First, in order to search for a context containing the symbol K, a context (context P) held in the context tree holding unit 302B is selected (steps W1 to W2),
It is checked whether the symbol K has been registered in the context P (step W3). If the symbol K has been registered, the same processing as steps Q9 to Q12 described above with reference to FIG. 58 is performed (steps W9 to W12).

On the other hand, if the symbol K is not registered in the context P, the encoding unit 306B outputs the ESC code (step W4) and the code changing unit 307B similarly to steps Q4 to Q5 in FIG. Is the code tree holding unit 301
A spray process is performed on the ESC leaf of the code tree stored in B (step W5). Thereafter, the code tree holding unit 30
1B stores the ID of the context P (root ID) in the context tree holding unit 3
02B, the node ID of the context P and the parent-child information are sent to the longest code detection unit 69.

The longest code detecting section 69 detects the ID (ID-0) of the leaf X (p) having the longest code length from the parent-child information (step W6). Then, the detected leaf X
The ID and ID-0 of (p) are sent to the leaf ID holding unit 68, and the ID-0 and the symbol stored in the ID-0 are latched by the latch 70.

The new node ID generating section 71 generates two new node IDs (ID-1, ID-2), and the parent / child information updating section 63 generates three IDs (ID-0, ID-ID).
1, ID-2), the parent-child information is updated, and registered in the node ID holding unit 65 of the code tree holding unit 301B. on the other hand,
The registered symbol K, the new ID (ID-2), and the symbol registered as ID-0 and ID-1 are registered as new leaves in the leaf ID holding unit 68 of the code tree holding unit 301B (step W7). .

By performing the above processing, the leaf having the longest code length becomes a node, and two new leaves are registered under this node. Then, the context P is changed (step W8), and the above processing is repeated until it is detected that the symbol K is registered in the context P. As described above, according to the data compression device according to the first modification of the embodiment of the present invention, in addition to the above-described effects on the encoding side of the above-described embodiment, the longest code (The distance from the root is the longest), and branches off the leaf X (p) to the symbol tree of symbols K and X (p). Make a new registration. This gives the "longest code length"
= "Least-occurring symbol", it is possible to minimize a decrease in coding efficiency due to an extension of the code length by 1 bit, thereby greatly improving the data compression processing speed and the data compression apparatus. Processing load can be greatly reduced.

(2) Description of the Decompression Side The data decompression device 4 according to the first modification of the present embodiment has the same configuration as that described above with reference to FIG. Code registration unit 407 in
B and the code tree holding unit 401B have the same internal configuration as the code registering unit 322B and the code tree holding unit 301B on the encoding side, respectively (see FIG. 66). Accordingly, the code registration unit 407B and the code tree holding unit 401B have the same configuration as the code registration unit 322B and the code tree holding unit 301B on the encoding side.
The process of newly registering the code of the decoded symbol in the code tree holding unit 401B is similar to the process on the encoding side. Therefore, the symbol K encoded on the encoding side
65 may be performed in the same manner as the processing (steps V1 to V11) described above with reference to FIG. 65. In step V10 in FIG. 65, the processing step W on the encoding side is performed.
7, W8 (see FIG. 67) may be performed.

As described above, according to the data restoring apparatus according to the first modification of the embodiment of the present invention, like the encoding side, the data tree having the longest code length in the code tree of the context P (from the root) Is the longest) leaf X (p) is detected,
By branching this leaf X (p) and newly registering the symbols registered in the symbols K and X (p) in the code tree, “the longest code length” = “the symbol with the lowest appearance frequency” Therefore, in addition to the effect on the restoration side of the above-described embodiment, a decrease in data decoding efficiency due to the extension of the code length by 1 bit can be minimized, and the processing speed of data decoding can be significantly increased. As a result, the processing load on the data restoration device can be significantly reduced.

Further, as described above, by making the registration processing on the symbol restoration side the same as the registration processing on the coding side, the code of the symbol coded on the coding side can be correctly decoded. There is an effect that can be. (C-2) Description of Second Modification of One Embodiment (1) Description of Encoding Side Also in the present embodiment, the configuration of the encoding side is the same as the configuration described above with reference to FIG.

The code registration unit 322B shown in FIG. 52 according to the present embodiment is used to branch a leaf newly registered on the code tree held by the code tree holding unit 301B and register a symbol. , New node ID generating section 61, latch 62, parent-child information updating section 63, and latest registration I
D holding unit 70 is provided, and a code tree holding unit 301B is provided.
Is provided with an external node (leaf ID) holding unit 64, an internal node (node ID) holding unit 65, an ESC-ID holding unit 66, and a code tree management unit 67.

Here, in the above configuration, the same reference numerals as those already described in FIG. 53 or FIG.
The description is omitted. The latest registration ID holding unit (branch position holding unit) 70 newly provided in the present embodiment includes:
This is to hold the ID of the leaf newly (newly) registered in the code tree held in the code tree holding unit 301B.

Code registration section 322B and code tree holding section 3
Since 01B has the above-described configuration, the code registration unit 322B branches the latest leaf in which the symbol is last registered in the code tree held in the code tree holding unit 301B, and newly registers the new leaf. The symbol K can be newly registered in the created leaf. Hereinafter, the above processing will be described in more detail with reference to processing steps X1 to X13 in FIG.

In the above-described processing, the latest registered leaf ID is stored in the latest registered ID storage unit 70,
New registration is performed by branching the ID. First, in order to search for a context including the symbol K, a context (context P) held in the context tree holding unit 302B is selected (steps X1 to X2), and the symbol K is registered in the context P. Is checked (step X3), and if registered, step W10 described above with reference to FIG.
-W13 (YES in step X3)
Steps X10 to X13 from the route).

On the other hand, when the symbol K is not registered in the context P, the encoding unit 306B outputs the ESC code (step X4), and the code changing unit 307B, similarly to steps W4 to W5 in FIG. Is the code tree holding unit 301
A spray process is performed on the ESC leaf of the code tree stored in B (step X5). Thereafter, the code tree holding unit 30
1B outputs the ID (root ID) of the context P to the latest registration ID holding unit 70 as it is.

In the latest registration ID holding unit 70, the context P
The leaf ID (ID-0) of the latest registered leaf X (p) corresponding to the code tree corresponding to the leaf ID of the code tree holding unit 301B
The symbols are sent to the holding unit 64 and the symbols stored in ID-0 and ID-0 are latched by the latch 62. New ID generator 6
1 generates two new IDs (ID-1, ID-2), and the parent / child information updating unit 63 generates three IDs (ID-0, ID-2).
D-1 and ID-2), the leaf X (p) is branched by updating the parent-child information (step X6), and this information is registered in the node ID holding unit 65 of the code tree holding unit 301B.

On the other hand, the leaf ID of the code tree holding unit 301B
The registration symbol K and the symbol registered in the leaf X (p) are registered as new leaves in the holding unit 64 (steps X7 and X8). A certain ID-2 is registered. Then, the context P is changed (step X9), and the above processing is repeated until it is detected that the symbol K is registered in the context P.

By performing the above processing, whenever a new symbol K is input, the latest registered leaf registered immediately before the input of the symbol K is divided and the symbol K is registered in this leaf. I do. As described above, according to the data compression apparatus according to the second modification of the embodiment of the present invention, new registration of a symbol in the code tree is performed by branching the leaf of the symbol registered immediately before and registering the new symbol in this leaf. By doing, "symbol of leaf registered just before" =
Since it can be approximated to "a symbol having a relatively long code length", the process of detecting the leaf having the longest code length can be omitted as described above in the first modification of this embodiment, and furthermore, data compression This has the effect of greatly improving the processing speed of.

(2) Description of the Decompression Side The configuration of the decompression side is the same as the configuration described above with reference to FIG. 62 similarly to the encoding side, and further, the code registration unit 407B and the code tree holding unit on the decompression side 401B is a code registration unit 322B and a code tree holding unit 3 on the encoding side, respectively.
It has the same internal configuration as 01B (see FIG. 68).

Therefore, since the code registration section 407B and the code tree holding section 401B have the same configuration as the code registration section 322B and the code tree holding section 301B on the encoding side, a first modification of the present embodiment is provided. Similarly to the decoding side in the example, the process of newly registering the code of the symbol decoded by the code registration unit 407B in the code tree holding unit 401B is performed in the same manner as the process on the encoding side.

For this reason, the decoding process of the symbol K coded by the encoding side on the restoration side in this embodiment is also performed by the process shown in FIG.
5 is performed in the same manner as the processing described above (steps V1 to V11). That is, the processing step V11 in FIG.
Also, the same processing as steps X6 to X8 in FIG. 69, which is the registration processing on the encoding side, is performed.

As described above, according to the data restoring apparatus according to the second modification of the embodiment of the present invention, the new registration of a symbol in the code tree is performed in the same way as the encoding side, in which the symbol registered just before is registered. Is registered in this leaf, it is possible to approximate “symbol of the leaf registered immediately before” = “symbol having a relatively long code length”. Therefore, in the first modified example of the present embodiment, As described above, the process of detecting the leaf having the longest code length can be omitted,
Further, there is an effect that the processing speed of data decoding is greatly improved.

By making the process of newly registering a symbol in a code tree the same as the process of registering on the encoding side, decoding of a symbol encoded on the encoding side can be performed accurately. There is also an effect that can be done.

In the above embodiment and each of the modifications, in order to switch the method described on the encoding side depending on the data or system to be encoded, which method is used for the header section prior to the transmission of the encoded data. May be added, and the restoration side may select the registration method used on the encoding side from the ID number.

[0357]

As described above in detail, according to the data compression method of the present invention, in the data compression method of encoding and compressing input data according to a history that has appeared in the past, And a context tree holding process for storing a context tree in which a combination of a context consisting of n consecutive data and a code tree for each context are stored. When the combination of the context tree is not held in the context tree holding process, the context tree new registration process of newly registering data in the context tree of the context tree holding process, and the combination of input data and context is held in the context tree holding process If not, a new code tree registration process of storing data in a new leaf obtained by branching a leaf as a data storage point of the code tree in the code tree holding process, and a set of input data and context A context change process that changes the context when the matching is not held in the context tree holding process, and a code that outputs a code according to the input data from the vertex of the code tree or a branch to a leaf where a specific code in the code tree is registered An output step, and a code length changing step of replacing a leaf in which a specific code in the input data or the code tree is registered with a node defined as a branch point other than the vertex of another leaf or the code tree. In the tree new registration process,
It is characterized by branching a leaf in which a specific code is registered, and registering the specific code and new data in the two new leaves obtained. In some cases, or at an early stage when the registration of the context held in the context tree holding process is not sufficient, a high coding rate can be obtained. If the code length changing step is performed before the above-described code tree new registration step, the code length of the code and the specific code is at least 2 bits. If the code length change step is performed after the new code tree registration step, the code of the specific code is changed. Can be reduced to 1 bit at a minimum, so that the coding efficiency is further improved. Furthermore, in the code tree new registration, new data registration is always 1
This is performed one by one, so that only symbols with reproducibility are always registered in the higher order of the code tree. This occurs because there is data that has been registered in the code tree but is not actually used. It is possible to prevent a decrease in coding efficiency, and thereby, there is an effect that coding efficiency after data registration is sufficiently performed is greatly improved.

According to the data compression method of the present invention described in claim 2, the specific code in the data compression method of the present invention described in claim 1 is an escape code defined in advance as data indicating unregistered data. By doing
The same effects as those of the data compression method of the present invention described in claim 1 can be obtained. Further, according to the data compression method of the present invention, in the code tree new registration process, among the leaves under the same context, the leaf having the longest distance from the root defined as the vertex of the code tree is branched and obtained. 2
The data stored in the branched leaf and the new data are registered in one new leaf (Claim 3), and the last registered leaf among the leaves under the same context is branched and obtained. Since the data stored in the branched leaf and the new data can be registered in the two new leaves (claim 4), the data compression method of the present invention according to claim 2 described above. In addition to the effects of the above, the code length of the least frequently used data that is rarely used can be lengthened, thereby minimizing the decrease in coding efficiency due to the extension of the code length by 1 bit. This has the effect of greatly improving the processing speed of. Further, the new data stored in the last registered leaf can be approximated as data having a relatively long code length, so that the processing speed of data compression is further improved.

According to the data restoring method of the present invention, in a data restoring method for decoding a code obtained by encoding input data in accordance with the history of past input data, the decoded data, A context tree holding process that holds a context tree in which a combination of the above is registered, a code tree holding process that holds an independent code tree for each context, and a code tree determination that determines a code tree of a code from data decoded immediately before The decoding process of decoding the code by scanning from the root meaning the apex of the code tree to the leaf as the data storage point according to the code, and if the reached leaf is a specific code in the code tree, the context The context change process to be changed, the code length changing process of assembling the leaf of the decoded data and the specific code with another leaf or a node as a branch point, and the decoding of the specific code. A new registration process of newly registering the data decoded in the code tree and a context tree registration process of registering the data registered in the new registration process in the context tree of the context tree holding process. The new data is registered by branching the same leaf as the leaf selected as the branch on the side, and the code length of the leaf divided into two is set in the new registration process of data in the same way as the encoding side. (The code length of the leaf before division + 1) bits, and the code length of the newly registered data and the code length of the specific code can be made a minimum of 2 bits, whereby the escape code can be decoded in a relatively large number. Data decoding efficiency, or in the initial stage where dictionary registration (symbol registration in the code tree) is not sufficient, the data decoding efficiency is greatly improved. There is an effect to be.

If the code length changing step is performed before the new data registration step, the code length of the decoded data code and escape code is at least 2 bits. If the code length changing step is performed after the new registration step, The code of the escape code can be reduced to 1 bit at a minimum, which has the effect of greatly improving the data decoding efficiency. Further, the new registration process can be performed on the restoration side in the same manner as on the encoding side, which has the advantage that the data encoded on the encoding side can be accurately decoded.

According to the data restoring method of the present invention described in claim 6, the specific code is an escape code defined in advance as data indicating unregistered data. The same effect as the effect in the data restoration method can be obtained. Further, according to the data compression apparatus of the present invention, in the data compression apparatus that encodes input data according to a history that has appeared in the past, an escape code defined in advance as data indicating that data has not been registered is used. Code tree holding means for holding a registered code tree, context tree holding means for holding a context tree in which a combination of input data and a context are registered, and encoding of an escape code and newly registering data in the context tree Code registration means for encoding the escape code and then branching the leaf as a data storage point of the escape code in the code tree and newly registering the data; and a combination of the input data and the context in the context tree. When not held, the context change means for changing the context and the input data or escape code from the top of the code tree are registered. Encoding means for outputting a code according to branch to the leaf that,
The encoded data and the escape code are characterized in that they are provided with a code updating means for replacing a leaf in which the escape code is registered with another leaf or node. , Or at an early stage when the registration of the context held in the context tree holding means is not sufficient, and the like, and there is an effect that a high coding rate can be obtained. In addition, if the code updating is performed by the code updating unit before the code is registered by the code registering unit, the code length of the code and the specific code is at least 2 bits. Is performed, the code of the escape code can be reduced to 1 bit at a minimum, which has the effect of greatly improving the coding efficiency. Further, since new registration of codes by the code registration means is always performed one by one, only data having reproducibility is always registered in the higher order of the code tree. It is possible to prevent a decrease in the coding efficiency caused by the existence of data that is not actually used, and this has the effect of greatly improving the coding efficiency after the data is sufficiently registered. Such an effect has the effect of dramatically improving the performance of the data compression device.

According to the data compression apparatus of the present invention, in the data compression apparatus which encodes input data in accordance with a history that has appeared in the past, the data is defined in advance as data indicating that data has not been registered. Code tree holding means for holding a code tree in which an escape code is registered; context tree holding means for holding a context tree in which a combination of input data and a context is registered; and encoding the escape code and storing the data in the context tree. Newly registered context registration means, branch position search means for searching for the leaf having the longest code length on the code tree, and leaf as a data storage point searched by the branch position search means after encoding the escape code Code registration means for registering new data by branching the context, and changing the context when the combination of input data and context is not held in the context tree Pulse changing means and encoding means for outputting a code in accordance with a branch from the top of the code tree to the leaf in which the input data or the escape code is registered; a leaf in which the encoded data and the escape code are registered and another leaf Alternatively, the present invention is characterized in that it comprises a code updating means for replacing a node, so that in addition to the effect of the data compression apparatus of the present invention described in claim 7, the least frequently used appearance frequency is low. The code length of the data can be lengthened, whereby the reduction of the coding efficiency due to the extension of the code length by 1 bit can be minimized and the processing speed of data compression can be greatly improved. In addition, there is an effect that the performance of the data compression device is dramatically improved.

Further, according to the data compression apparatus of the present invention, in a data compression apparatus which encodes input data in accordance with a history that has appeared in the past, data is defined in advance as data indicating that data has not been registered. Code tree holding means for holding a code tree in which an escape code is registered, context tree holding means for holding a context tree in which a combination of input data and a context are registered, and encoding the escape code,
Context registration means for newly registering data in the context tree, branch position holding means for holding the position of a leaf as a data storage point newly registered in the code tree, and branch position holding means after encoding the escape code Code registering means for branching the leaf at the position held in and newly registering data, and context changing means for changing the context when the combination of the input data and the context is not held in the context tree,
An encoding means for outputting a code according to a branch from a vertex of the code tree to a leaf in which the input data or the escape code is registered; and a leaf in which the encoded data and the escape code are registered and another leaf or a branch point. In addition to the effect of the data compression apparatus according to the present invention, the new data stored in the leaf registered last is relatively small in code. Since the data can be approximated as long data, the processing speed of data compression is greatly improved, and the processing load of the data compression apparatus is greatly reduced.

[0364] According to the data restoration apparatus of the present invention, in a data restoration apparatus for decoding a code obtained by encoding input data in accordance with a history of past input data, data unregistration is indicated in advance. Code tree holding means for holding a code tree in which escape codes defined as data are registered; context holding means for holding a context tree in which a combination of decoded data and context is registered; Code tree determining means for determining the code tree, decoding means for scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code, and decoding the code, and the arrived leaf was an escape code. In the case, the context change means for changing the context and the leaf of the decoded data and escape code are used as another leaf or a node as a branch point Code updating means for rearrangement, code decoding means for branching the escape code leaf when the escape code is decoded and newly registering the decoded data, and data registered by the code registration means to be registered in the context tree of the context holding means If the data is such that the escape code is decoded in a relatively large amount, or if the registration of the context held in the context tree holding means is not sufficient, etc. Has the effect of obtaining a high decoding rate. Further, if code updating is performed by the code updating means before code registration by the code registering means, the code length of the code and the specific code can be reduced to a minimum of two.
If the code is updated by the code updating means after the registration of the code by the bit and code registering means, the code of the escape code can be reduced to one bit at a minimum, which has the effect of further improving the decoding efficiency significantly. . Further, new registration of codes to be decoded by the code registration means is always performed one by one, so that only data having reproducibility is always registered in the higher order of the code tree. However, it is possible to prevent a decrease in decoding efficiency caused by the presence of data that is not actually used, and this has the effect of greatly improving the decoding efficiency after data has been sufficiently registered. Such an effect has an effect of dramatically improving the performance of the data restoration device.

Further, according to the data restoration apparatus of the present invention, in a data restoration apparatus for decoding a code obtained by encoding input data in accordance with a history of past input data, data unregistered in advance is indicated. Code tree holding means for holding a code tree in which escape codes defined as data are registered; context holding means for holding a context tree in which a combination of decoded data and context is registered; A code tree determining means for determining a code tree, a decoding means for scanning from a root meaning a vertex of the code tree according to the code to a leaf as a data storage point to decode the code, and the leaf that has arrived is an escape code. In this case, the context change means for changing the context and the leaf of the decrypted data and escape code may be used as another leaf or as a branch point. Code updating means, a branch position searching means for searching for a position of a leaf having the longest code length in a code tree, and a leaf searched by the branch position searching means after encoding an escape code to obtain data. 11. The data restoration method according to claim 10, comprising a code registration means for newly registering and a context tree registration means for registering data registered by the code registration means in a context tree of the context holding means. In addition to the effect of the device, the code length of the least frequently used data that is rarely used can be lengthened, thereby minimizing the decrease in coding efficiency due to the code length being extended by one bit and restoring the data. Has the effect that the processing speed of the data restoration device can be greatly improved, and also has the effect that the performance of the data restoration device can be dramatically improved.

According to the data restoring apparatus of the present invention, in a data restoring apparatus for decoding a code obtained by encoding input data in accordance with a history of past input data, data unregistered in advance is indicated. Code tree holding means for holding a code tree in which escape codes defined as data are registered; context holding means for holding a context tree in which a combination of decoded data and context is registered; A code tree determining means for determining a code tree, a decoding means for scanning from a root meaning a vertex of the code tree according to the code to a leaf as a data storage point to decode the code, and the leaf that has arrived is an escape code. In the case, the context change means for changing the context and the leaf of the decoded data and escape code are used as another leaf or a node as a branch point Code updating means for rearranging, branch position holding means for holding the position of a leaf newly registered in the code tree, and after encoding the escape code, branching the leaf at the position held in the branch position holding means. 35. The apparatus according to claim 34, further comprising code registering means for newly registering data by means of the registering means, and context tree registering means for registering the data registered by the code registering means in a context tree of the context holding means. In addition to the effects of the data restoration apparatus of the present invention, new registration of data can be performed on the leaf in which the last registered data is stored, and the data stored in the last registered leaf is relatively signed. Since the data can be approximated as long data, the code length is 1
This has the effect of minimizing the decrease in decoding efficiency due to bit lengthening and greatly improving the data restoration processing speed, and also has the effect of dramatically improving the performance of the data restoration device.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a technique related to the present invention.

FIG. 2 is a block diagram for explaining a technique related to the present invention.

FIG. 3 is a block diagram for explaining a technique related to the present invention.

FIG. 4 is a block diagram for explaining a technique related to the present invention.

FIG. 5 is a block diagram for explaining a technique related to the present invention.

FIG. 6 is a block diagram for explaining a technique related to the present invention.

FIG. 7 is a block diagram for explaining a technique related to the present invention.

FIG. 8 is a block diagram for explaining a technique related to the present invention.

FIG. 9 is a principle block diagram of the present invention.

FIG. 10 is a principle block diagram of the present invention.

FIG. 11 is a principle block diagram of the present invention.

FIG. 12 is a principle block diagram of the present invention.

FIG. 13 is a principle block diagram of the present invention.

FIG. 14 is a principle block diagram of the present invention.

FIG. 15 is a block diagram showing a configuration of a data compression device and a data decompression device as technology 1 related to the present invention.

FIG. 16A is a diagram illustrating an example of a storage format of a context tree. (B) is a diagram showing the parent-child relationship of the dictionary.

FIG. 17 is a diagram for describing an initial state of a code tree.

FIG. 18 is a diagram illustrating an example of an array for storing a code tree.

FIGS. 19A and 19B are diagrams for explaining a basic operation of code update of a spray code and an example of code update of a spray code, respectively.

FIG. 20 is a flowchart for explaining an encoding procedure according to Related Technique 1;

FIGS. 21A and 21B are diagrams for explaining a procedure for updating a context tree and a code tree according to Related Art 1;

FIGS. 22A and 22B are diagrams for explaining a procedure for updating a context tree and a code tree according to Related Art 1;

FIGS. 23A and 23B are diagrams for explaining a procedure for updating a context tree and a code tree according to Related Art 1;

FIGS. 24A and 24B are diagrams for explaining a procedure for updating a context tree and a code tree according to Related Art 1;

FIGS. 25A and 25B are diagrams for explaining a procedure for updating a context tree and a code tree according to Related Art 1;

FIGS. 26A and 26B are diagrams for explaining a procedure for updating a context tree and a code tree according to Related Art 1;

FIGS. 27A and 27B are diagrams for explaining a procedure of updating a context tree and a code tree according to Related Art 1;

FIGS. 28A and 28B are diagrams for explaining a procedure for updating a context tree and a code tree according to Related Art 1;

FIG. 29 is a diagram for describing an example of a character string according to Related Art 1 after encoding.

FIGS. 30A and 30B are diagrams showing an algorithm of a procedure for creating a context tree.

FIG. 31 is a flowchart for explaining a decoding procedure according to Related Technique 1;

FIG. 32 is a block diagram illustrating a configuration of a data compression device and a data decompression device according to a technique 2 related to the present invention.

FIG. 33 is a block diagram showing a configuration of a data compression device according to Related Art 2;

FIG. 34 is a block diagram illustrating a configuration of an encoding unit according to Related Technology 2.

FIG. 35 is a flowchart for describing an encoding procedure according to Related Technique 2;

FIG. 36 is a flowchart for explaining a code output procedure according to Related Art 2;

FIG. 37 is a flowchart illustrating a procedure for rearranging a code tree according to Related Art 2;

FIG. 38 is a block diagram for explaining a configuration of a data restoration device according to Related Art 2;

FIG. 39 is a block diagram for describing a configuration of a decoding unit according to Related Technology 2.

FIG. 40 is a flowchart for describing a decoding procedure according to Related Technique 2;

FIG. 41 is a flowchart for describing a decoding procedure according to Related Technique 2;

FIG. 42 is a block diagram for describing a configuration of a data compression device according to a first modification of Related Art 2.

FIG. 43 is a flowchart for describing an encoding procedure according to a first modification of Related Art 2.

FIG. 44 is a block diagram for explaining a configuration of a data restoration device according to a first modification of Related Art 2.

FIG. 45 is a flowchart for describing a decoding procedure according to a first modification of Related Art 2;

FIG. 46 is a block diagram illustrating a configuration of a data compression device according to a second modification of Related Art 2.

FIG. 47 is a flowchart for describing an encoding procedure according to a second modification of Related Art 2;

FIG. 48 is a block diagram illustrating a configuration of a data restoration device according to a second modification of Related Art 2.

FIG. 49 is a flowchart for describing a decoding procedure according to a second modification of Related Art 2;

FIG. 50 is a flowchart for describing an encoding procedure according to a third modification of Related Art 2;

FIG. 51 is a flowchart for describing a decoding procedure according to a third modification of Related Art 2;

FIG. 52 is a block diagram illustrating a configuration of a data compression device according to an embodiment of the present invention.

FIG. 53 is a block diagram illustrating a configuration of a code registration unit and a code tree holding unit according to the embodiment;

FIG. 54 is a diagram for explaining the operation of the data compression device according to the embodiment;

FIG. 55 is a view for explaining the operation of the data compression device according to the embodiment;

FIG. 56 is a view for explaining the operation of the data compression device according to the embodiment;

FIGS. 57A and 57B are diagrams illustrating examples of a code tree and a context tree, respectively.

FIG. 58 is a flowchart for describing an encoding procedure according to the embodiment;

FIG. 59 is a flowchart for explaining an encoding procedure according to the embodiment;

FIGS. 60A and 60B are diagrams showing a newly registered state of a code according to the present embodiment.

FIG. 61 is a flowchart for explaining another procedure of the encoding according to the embodiment;

FIG. 62 is a block diagram for explaining the configuration of a data restoration device according to the present embodiment.

FIG. 63 is a view for explaining the operation of the data restoration device according to the present embodiment;

FIG. 64 is a view for explaining the operation of the data restoration device according to the present embodiment;

FIG. 65 is a flowchart for explaining a decoding procedure according to the embodiment;

FIG. 66 is a block diagram illustrating a configuration of a code registration unit and a code tree holding unit according to a first modification of the present embodiment.

FIG. 67 is a flowchart for describing an encoding procedure according to a first modification of the present embodiment.

FIG. 68 is a block diagram illustrating a configuration example of a code registration unit and a code tree holding unit according to a second modification of the present embodiment.

FIG. 69 is a flowchart for describing an encoding procedure according to a second modified example of the present embodiment.

FIGS. 70A and 70B are diagrams for explaining the principle of multi-level arithmetic coding.

FIGS. 71 (a) and (b) are flowcharts showing a conventional multi-value arithmetic coding procedure for compressing in character units.

FIG. 72 is a diagram illustrating an example of an algorithm of multi-level arithmetic coding.

FIGS. 73A and 73B are diagrams for explaining the principle of spray coding.

FIG. 74 is a diagram for describing the principle of probability statistical coding.

75 (a) and (b) are diagrams showing an example of registration of a context tree.

[Explanation of symbols]

1,3 Data compression device 2,4 Data decompression device 11,22 Context collection process 12,21 Spray coding process 41 Upper node determination unit 42 Node number management unit (memory) 43 Position determination unit 44,48 Latch 45 Stack 46 Lower Node discriminating unit 47 Leaf / node discriminating unit 61 New node ID generating unit 62 Latch 63 Parent / child information updating unit 64 External node (leaf ID) holding unit 65 Internal node (node ID) holding unit 66 ESC-ID holding unit 67 Code tree management Unit 68 external node / ESC-ID (leaf ID) holding unit 69 longest code detecting unit (branch position searching unit) 70 latest registration ID holding unit (branch position holding unit) 100, 200 prefix data holding unit 100A-1 to 100A -N, 200A-1 to 200A
-N Prefix data holding unit 101, 201 History holding unit 101A, 201A Context history holding unit 102, 202, 107, 207, 301, 401 Code tree holding unit 102A, 202A, 107A, 207A, 301B,
401B Code tree holding units 103, 203, 403 Code tree determining means 103A, 203A Code tree determining unit 104 Code output means 104A, 104A ', 306B Coding units 105, 205 Code length changing means 105A, 205A Code tree updating unit 106, 206 Prefix data update unit 106A, 206A Context update unit 108 Context determination unit 108A Context determination unit 109 Escape code output unit 110, 208, 305, 405 Context change unit 110A, 210A, 305B, 403B Context change unit 111 Code output unit 112 , 209 history registration means 113, 114, 115, 212, 304, 309, 3
11, 407, 410, 412 Code registration unit 112A, 212A, 322B, 407B Code registration unit 116, 117, 213 Control unit 204, 404 Decoding unit 204A, 204A ', 404B Decoding unit 303 Context registration unit 303B, 408B Context registration unit 302, 402 Context tree holding unit 302B, 402B Context tree holding unit 306 Encoding unit 307, 406 Code updating unit 406B Code changing unit 308, 409 Branch position holding unit 310, 411 Branch position searching unit 321B, 421B Context holding unit 408, 413, 414 Context tree registration means 409B Latch 511 Context collection 512 Dynamic variable length coding

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Yoshida 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term within Fujitsu Limited (reference) 5J064 AA03 BA00 BA09 BA10 BA11 BB05 BB06 BC02 BC27 BC28 BC29 BD04

Claims (12)

[Claims] 1. A data compression method for encoding and compressing input data in accordance with a history that has appeared in the past, wherein a context tree in which a combination of input data and a context consisting of n consecutive data is registered. A context tree holding process for holding; a code tree holding process for holding a code tree independent for each context; and a case where the combination of the input data and the context is not held in the context tree holding process. A context tree new registration step of newly registering the data in the context tree of the holding step; and a code tree of the code tree holding step when the combination of the input data and the context is not held in the context tree holding step. A code tree new registration step of storing the above data in a new leaf obtained by branching a leaf as a data storage point of the above; A context changing step of changing a context when not held in a holding step; and a code for outputting a code according to a branch from a vertex of the code tree to a leaf in which the input data or a specific code in the code tree is registered. An output step and a code length changing step of replacing a leaf in which a specific code in the input data or the code tree is registered with a node defined as a branch point other than the vertex of another leaf or the code tree. In the code tree new registration step, a leaf in which the specific code is registered is branched, and the specific code and new data are registered in the obtained two new leaves. 2. A data compression method for encoding and compressing input data according to a history that has appeared in the past, comprising: a code tree holding step of holding a code tree in which an escape code defined in advance as data indicating unregistration is registered And a context tree holding process for holding a context tree in which a combination of input data and a context consisting of n consecutive data items is registered. The combination of the input data and the context is a context tree holding process. When not held, when a context tree new registration process of newly registering the data in the context tree of the context tree holding process, and when the combination of the input data and the context is not held in the context tree holding process A code tree new registration step of storing the data in a new leaf obtained by branching a leaf as a code tree data storage point in the code tree holding step; A context change process for changing the context when the combination of the input data and the context is not held in the context tree holding process; and a process from the top of the code tree to the leaf where the input data or the escape code is registered. A code output process of outputting a code according to a branch, and a code length changing process of replacing a leaf in which the input data or the escape code is registered with a node defined as a branch point other than a vertex of another leaf or the code tree. In the code tree new registration step, the leaf in which the escape code is registered is branched, and the escape code and the new data are registered in the obtained two new leaves. Data compression method. 3. In the code tree new registration process, among the leaves under the same context, the leaf having the longest distance from the root defined as the vertex of the code tree is branched and obtained.
3. The data compression method according to claim 2, wherein the data stored in the branched leaf and the new data are registered in one new leaf. 4. In the code tree new registration step, among the leaves under the same context, the last registered leaf is branched, and the two new leaves obtained include the data stored in the branched leaf. 3. The data compression method according to claim 2, wherein new data and new data are registered. 5. A data restoration method for decoding a code obtained by encoding input data according to a history of past input data, comprising: a context tree holding step of holding a context tree in which a combination of the decoded data and a context is registered; A code tree holding step of holding an independent code tree according to a context; a code tree determining step of determining a code tree of the code from data decoded immediately before; and a vertex of the code tree according to the code A decoding process in which a code is decoded by scanning from the root to a leaf as a data storage point, and when the reached leaf is a specific code in a code tree,
A context change step of changing a context; a code length change step of rearranging the decoded data and the leaf of the specific code with another leaf or a node as a branch point; and decoding the data decoded into a code tree when the specific code is decoded. A new registration step of newly registering, and a context tree registration step of registering data registered in the new registration step in a context tree of the context tree holding step, wherein the encoding side selects a branch in the new registration step. A data restoring method, characterized in that the same leaf as the extracted leaf is branched and new data is registered. 6. A data restoration method for decoding a code obtained by encoding input data according to a history of past input data, wherein a code tree in which an escape code defined in advance as data indicating that data has not been registered is stored. A code tree holding step, a context tree holding step of holding a context tree in which a combination of decoded data and a context is registered, a code tree determining step of determining a code tree of the code from data decoded immediately before, A decoding process of scanning the root of the code tree according to the code from the root meaning the vertex to the leaf as the data storage point to decode the code, and when the reached leaf is the escape code,
A context change step of changing a context, a code length change step of rearranging the decoded data and the escape code leaf with another leaf or a node as a branch point, and a data tree decoded when the escape code is decoded. A new registration step of newly registering, and a context tree registration step of registering data registered in the new registration step in a context tree of the context tree holding step, wherein the encoding side selects a branch in the new registration step. A data restoring method, characterized in that the same leaf as the extracted leaf is branched and new data is registered. 7. A data compression apparatus for encoding input data in accordance with a history of past occurrences, comprising: a code tree holding means for holding a code tree in which an escape code defined in advance as data indicating unregistered data is registered. A context tree holding means for holding a context tree in which a combination of input data and a context is registered; a context registration means for newly registering the data in the context tree after encoding the escape code; Code registration means for branching a leaf as a data storage point of the escape code and then registering the new data, and a combination of the input data and the context is stored in a context tree. When there is no context change means for changing the context, the above input data or escape code is registered from the top of the code tree. Encoding means for outputting a code according to a branch to a certain leaf, and code updating means for replacing the leaf in which the encoded data and the escape code are registered with another leaf or node. Characteristic data compression device. 8. A data compression apparatus for encoding input data in accordance with a history of past appearances, comprising: a code tree holding means for holding a code tree in which an escape code defined in advance as data indicating data not registered is registered. A context tree holding unit that holds a context tree in which a combination of input data and a context is registered; a context registration unit that newly registers the data in the context tree after encoding the escape code; Branch position searching means for searching for a leaf having the longest code length of the above, and after encoding the escape code, the branch as a data storage point searched by the branch position searching means is branched to newly store the data. Code registering means for registering; context changing means for changing the context when the combination of the input data and the context is not held in the context tree; Encoding means for outputting a code in accordance with a branch from the top of the code tree to the input data or the leaf in which the escape code is registered; a leaf in which the encoded data and the escape code are registered and another leaf or node And a code updating means for replacing the data. 9. A data compression apparatus for encoding input data according to a history of past appearances, comprising: a code tree holding means for holding a code tree in which an escape code defined in advance as data indicating data not registered is registered. A context tree holding means for holding a context tree in which a combination of input data and a context is registered; a context registration means for newly registering the data in the context tree after encoding the escape code; Branch position holding means for holding the position of a leaf as a newly registered data storage point; and after encoding the escape code, branching the leaf at the position held by the branch position holding means to Code registering means for newly registering data, and changing the context when the combination of the input data and the context is not stored in the context tree A context changing unit; an encoding unit that outputs a code according to a branch from a vertex of the code tree to the input data or the leaf in which the escape code is registered; and a leaf in which the encoded data and the escape code are registered. A data compression device comprising code updating means for replacing a node as another leaf or a node as a branch point. 10. A data restoration device for decoding a code obtained by encoding input data according to a history of past input data, wherein a code tree in which an escape code defined in advance as data indicating data not registered is stored. Code tree holding means; context tree holding means for holding a context tree in which a combination of decoded data and context is registered; code tree determining means for determining a code tree of the code from data decoded immediately before; Decoding means for scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code to decode the code, and when the reached leaf is the escape code,
Context changing means for changing the context; code updating means for changing the decoded data and the escape code leaf to another leaf or a node as a branch point; branching the escape code leaf when decoding the escape code Code registration means for newly registering the decoded data, and context tree registration means for registering the data registered by the code registration means in the context tree of the context tree holding means. , Data restoration device. 11. A data restoration apparatus for decoding a code obtained by encoding input data in accordance with a history of past input data, wherein a code tree in which an escape code defined in advance as data indicating data not registered is stored. Code tree holding means; context tree holding means for holding a context tree in which a combination of decoded data and context is registered; code tree determining means for determining a code tree of the code from data decoded immediately before; Decoding means for scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code to decode the code, and when the reached leaf is the escape code,
Context changing means for changing the context; code updating means for changing the decoded data and the escape code leaf to another leaf or a node as a branch point; searching for the position of the leaf having the longest code length in the code tree Branch position searching means, a code registering means for encoding the escape code, branching the leaf searched by the branch position searching means and newly registering the data, A data restoration apparatus characterized by comprising context tree registration means for registering in a context tree of a context tree holding means. 12. A data restoration apparatus for decoding a code obtained by encoding input data in accordance with a history of past input data, wherein a code tree in which an escape code defined in advance as data indicating that data has not been registered is stored. Code tree holding means; context tree holding means for holding a context tree in which a combination of decoded data and context is registered; code tree determining means for determining a code tree of the code from data decoded immediately before; Decoding means for scanning from the root meaning the vertex of the code tree to the leaf as the data storage point according to the code to decode the code, and when the reached leaf is the escape code,
Context changing means for changing the context; code updating means for assembling the decoded data and the escape code leaf with another leaf or a node as a branch point; holding the position of a leaf newly registered in the code tree Branch position holding means, code encoding means for encoding the escape code, branching a leaf at a position held in the branch position holding means, and registering the data newly, and the code registration means A data restoration device comprising a context tree registration unit for registering registered data in a context tree of a context tree holding unit.