JP2693338B2 - Error control processing method in data compression / decompression processing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression / decompression process in a communication system complying with universal code, and even if an error occurs on the decompression side, the universal coding / decoding process does not have to be redone from the beginning. Error control in the data compression / decompression process that enables the entire data to be decompressed even if an error occurs on the decompression side in the data compression / decompression process in the storage system conforming to the universal code. It relates to a processing method.

In recent years, various kinds of data such as character codes, vector information, and images have been handled by computers, and the amount of data handled has been increasing rapidly. When handling such a large amount of data, it is necessary to omit redundant parts in the data and compress the data amount in order to reduce the storage capacity and realize high-speed transmission.

Various methods of data compression have been proposed, but as a method of realizing data compression without knowing the statistical properties of the data to be compressed,
Universal codes have been proposed. As a typical method of this universal code, an arithmetic code that accumulates appearance probabilities and a Giburempel (Zi
v-Lempel) code, and this Dibullenpel code is roughly divided into two algorithms, a slide dictionary type and a dynamic dictionary type.

The LZSS code has been proposed as an improvement of the slide dictionary type algorithm, and the LZW code has been proposed as an improvement of the dynamic dictionary type algorithm. In order to make the data compression / decompression process using such a universal code practical, it is necessary to construct a configuration that can appropriately handle an error.

[0005]

2. Description of the Related Art First, a data encoding process using an LZW code and its data restoration process will be described.
Error control processing of the conventional data compression / decompression processing in a communication system adopting the data compression / decompression processing format by the LZW code, and conventional data compression / decompression processing in the storage system adopting the data compression / decompression processing format by the LZW code. The error control process will be described. In the following explanation, following the name used in information theory,
One word of data is called a character, and a string of data connected together is called a character string.

FIG. 13 shows a processing flow of data encoding processing by the LZW code, and FIG. 14 shows a processing flow of data restoration processing by the LZW code. First, the data encoding process using the LZW code will be described with reference to FIG. In the data encoding process using the LZW code, the input data is decomposed into different character strings, and this character string is managed in a dictionary together with a reference number (dictionary number). By replacing the longest matching character string registered in the dictionary with the reference number string, a long character string is represented by a short reference number to perform encoding.

Here, as for the method of registering a character string in the dictionary, as shown in FIG. 15, for a newly registered character string other than a single character, the reference number registered up to that point and the subsequent one character are used. The composition is expressed by the combination of and registered.

That is, when executing the data encoding processing by the LZW code, as shown in the processing flow of FIG. 13, first, in step 1, there is a possibility that it may appear in the character string to be encoded. All certain single characters are registered in the dictionary, and the maximum number N of reference numbers is set to the number of single character types. Next, in step 2, the first character K of the input data to be encoded is input, and the reference number of the character K is set as the initial character string ω. Then, in step 3, the next character K is read from the input data to be encoded, and in subsequent step 4, the character string ωK that is a combination of the initial character string ω representing the reference number and the read character K is Determine whether it is registered in the dictionary.

When it is determined in step 4 that the character string ωK is registered in the dictionary, the process proceeds to step 5, the reference number of this character string ωK is set as a new initial character string ω, and the subsequent step In step 6, it is determined whether or not the processing has been completed for all the characters of the input data to be encoded. If it is determined that the processing has not been completed, the process returns to step 3 to search for the longest matching character string. When it is determined that the process has ended, the process proceeds to step 8 to output the reference number of the initial character string ω and end the process.

On the other hand, when it is determined in step 4 that the character string ωK is not registered in the dictionary, the process proceeds to step 7 in response to the character string indicated by the initial character string ω being the longest match character string. Then, the reference number of the initial character string ω is output, and the character string ωK is added to the reference number and registered in the dictionary. Then, the reference number of one character K following the initial character string ω is set as a new initial character string ω, and the maximum value of the reference number is incremented by 1 before proceeding to step 6. Then, the search for the next longest matching character string is started.

According to FIG. 16, L according to this processing flow
The ZW code generation will be specifically described. Step 1
In accordance with the processing of 1, the character a is registered in the dictionary together with the reference number 1, the character b is the reference number 2, and the character c is registered with the reference number 3.
Next, according to the process of step 2, the first character a of the input data is read and its reference number 1 is set as the initial character string ω. Then, according to the process of step 3,
The second character b of the input data is read out, and according to the process of step 4, it is determined that the character string 1b (= ab) is not registered in the dictionary, and according to the process of step 7, the first character string The reference number 1 of ω is output, and the character string 1b is registered with the reference number 4 in the dictionary.
Further, the reference number 2 of this character b is set as a new initial character string ω.

Then, the third character a of the input data is read according to the processing of step 3, and it is determined according to the processing of step 4 that the character string 2a (= ba) is not registered in the dictionary. Then, according to the process of step 7, the reference number 2 of the initial character string ω is output, and
The character string 2a is registered in the dictionary together with the reference number 5, and the reference number 1 of this character a is set as a new initial character string ω.

Then, the fourth character b of the input data is read according to the processing of step 3, and it is determined that the character string 1b is registered in the dictionary according to the processing of step 4, and step 5 is executed. According to the processing of, the reference number 4 of this character string 1b is set as a new initial character string ω. Then, the fifth character c of the input data is read according to the process of step 3, and it is determined that the character string 4c (= abc) is not registered in the dictionary according to the process of step 4, According to the processing of 7, the reference number 4 of the initial character string ω is output and the character string 4
c is registered in the dictionary together with the reference number 6, and the reference number 3 of this character c is set as a new initial character string ω. By repeating the same processing thereafter, the encoding as shown in FIG. 16 is executed.

Next, the data restoration processing using the LZW code will be described with reference to FIG. The data restoration processing using the LZW code has a configuration of performing data restoration by executing the inverse transformation processing of the data encoding described in FIG.

That is, when the data restoration processing by the LZW code is executed, as shown in the processing flow of FIG. 14, first, at step 1, all the characters that may appear in the restored character string are displayed. Register a single character in the dictionary,
The maximum number N of reference numbers is set to the number of single character types.
Next, in step 2, the first code (CODE) of the input data (reference number string) to be restored is read, and OLDc
Set it as ode and search the dictionary for this CO
Find the letter K pointed to by DE and output it. Here, the output character K is set to char for later exception processing.

Then, in step 3, the next code (CODE) is read from the input data to be restored and set as NEWcode. Then, in step 4, it is checked whether the CODE read in step 3 is registered in the dictionary. When it is determined in step 4 that CODE is registered in the dictionary, the process proceeds to step 5, the character string ωK pointed to by this CODE is read from the dictionary, and in step 6 that follows,
The character K of this character string ωK is stored in the stack, the reference number ω of this character string ωK is set as a new CODE, and the process returns to step 5.

When it is determined that CODE reaches the state of indicating one character by recursively executing the processes of steps 5 and 6, the process proceeds to step 7, and the character string stacked in step 6 is deleted. LILO (Last In Fast O
ut) format and pops up and outputs, and OLDcod
A reference number is added to the character string ωK, which is a combination of the previously used reference number ω set in e and the first character of the character string restored this time, and is registered in the dictionary. Then, the first character of the restored character string is set to char for later exception processing, the CODE of NEWcode is set as OLDcode, and the maximum value of the reference number is incremented by one.

When the processing of step 7 is completed, the process proceeds to step 8 to judge whether the processing has been completed for all codes of the input data to be restored, and when it is judged that the processing has not been completed, By returning to step 3, the restoration process of the next code is executed, and when it is judged that the process is finished, the process is finished.

When it is determined in step 4 that the CODE read in step 3 is not registered in the dictionary, the process proceeds to step 9 and the following exception processing is executed. Here, such a state occurs when the immediately preceding reference number is referred to in encoding. From this, in step 9, char is output, OLDcode is set as CODE, a combination of OLDcode and char is set as NEWcode, and the process proceeds to step 5.

According to FIG. 17, L according to this processing flow
The decoding process of the ZW code will be specifically described. According to the process of step 1, the character a is the reference number 1 and the character b is
Is registered in the dictionary together with the reference number 2 and the character c together with the reference number 3. Next, according to the process of step 2, the leading code 1 of the input data is read out and the character a pointed to by the code 1 is read.
Is output. Then, the second code 2 of the input data is read according to the process of step 3, and step 5
Or the character b pointed to by the code 2 is output in accordance with the process of step 7, and the character string 1b which is a combination of the previously processed code 1 and the first character b of the character string restored this time is stored in the dictionary together with the reference number 4. Be registered with.

Then, the third code 4 of the input code string is read according to the processing of step 3, and the character string ab pointed to by the code 4 is output according to the processing of steps 5 to 7. A character string 2a, which is a combination of the code 2 processed last time and the first character a of the character string restored this time, is registered in the dictionary together with the reference number 5. By repeating the same processing thereafter, the encoding as shown in FIG. 17 is executed, but when the sixth code 8 of the input data is read, the code 8 is the dictionary at the time of this restoration. Not registered in. From this, the exception process is executed according to the process of step 9, and the character string 5b obtained by adding the first character b of the previously restored character string ba to the previously processed code 5 is obtained, and by restoring this, the character string 5b is obtained. The character string bab pointed to by is obtained and output, and the character string 5b obtained by adding the first character b of the character string restored this time to the previously processed code 5 is registered in the dictionary together with the reference number 8. .

Next, the error control processing of the conventional data compression / decompression processing in the communication system adopting the data compression / decompression processing format by the LZW code and the conventional error control processing in the storage system adopting the data compression / decompression processing format by the LZW code. The error control process of the data compression / decompression process will be described.

FIG. 18 shows data compression by the LZW code.
An error control processing flow of a conventional data compression / decompression processing in a communication system that adopts the decompression processing form, and FIG. 19 shows a circuit configuration for realizing this control processing flow.

That is, in the conventional communication system, the compression side clears the dictionary data to the one for single character registration in step 1, and then in step 2, universally encodes the input data to be encoded. As a result, compressed data is generated, and in subsequent step 3, dictionary data is accumulated in synchronization with this universal encoding. Then, in step 4, the generated compressed data is transmitted to the decompression side. At this time, in step 5, the error detection code is added, and if there is a retransmission request due to a communication error from the decompression side, the compressed data is retransmitted in response to the request.

Then, in the subsequent step 6, it is judged whether or not there is a resend request due to a restoration error from the restoration side. When it is judged that there is no resend request, the process proceeds to step 7,
It is determined whether or not it is the final data to be encoded. If it is the final data, the process is ended, and if it is not the final data, the process returns to step 2 to continue the compressed data generation / transmission process. When it is determined in step 6 that there is a retransmission request, the process proceeds to step 8, the input data is re-input, and the process returns to step 1 to repeat the generation / transmission process of the compressed data from the beginning. .

On the other hand, the decompression side clears the dictionary data to the one registered in single character at step 9, and then at step 10, according to the error detection code added to the compressed data transmitted from the compression side. It detects whether an error has occurred in communication and issues a resend request when an error has occurred. Since this resend processing has a configuration in which both the compression side and the decompression side have a buffer memory and retransmits data between the buffer memories, universal encoding processing and decompression on the compression side are performed. It does not affect the universal decoding process on the side and does not result in the retransmission request described in step 6. Subsequently, in step 11, the compressed data transmitted from the compression side is received, and in step 12, the restored compressed data is generated by universally decoding the received compressed data,
In the following step 13, dictionary data is accumulated in synchronization with this universal decoding.

Then, in the following step 14, it is judged whether or not a restoration error has occurred during the universal decoding process, and when it is determined that the restoration error does not occur, the process proceeds to step 15 and the final data to be restored. If it is the final data, the process is ended. If it is not the final data, the process returns to step 11,
Continue the compressed data reception process and the decompressed data generation process. When it is determined in step 14 that a decompression error has occurred, the process proceeds to step 16, where a resend request due to a decompression error is issued to the compression side, and in the following step 17, input data is re-input and step 9 By returning to step 1, the process of receiving compressed data and the process of generating decompressed data are restarted from the beginning.

Thus, in the data compression / decompression process of the conventional communication system using the universal code, when a decompression error occurs on the decompression side, the compression side redoes the coding process from the beginning to generate compressed data. It adopted a configuration in which it is retransmitted to the restoration side.

FIG. 20 shows data compression by the LZW code.
An error control processing flow of conventional data compression / decompression processing in a storage system that adopts the decompression processing form, and FIG. 21 shows a circuit configuration for realizing this control processing flow.

That is, in the conventional storage system, the compression side clears the dictionary data to the one for single character registration in step 1, and then in step 2, universally encodes the input data to be encoded. As a result, compressed data is generated, and in subsequent step 3, dictionary data is accumulated in synchronization with this universal encoding. Subsequently, in step 4, an error correction code is added to the generated compressed data and stored in a storage device, and in the following step 5, it is determined whether it is the final data to be encoded, and the final data is determined. If it is, the process is terminated, and if it is not the final data, the process returns to step 2 to continue the generation / storing process of the compressed data.

On the other hand, the restoring side clears the dictionary data to the one registered as a single character in step 6, and then in step 7, according to the error correction code added to the stored data read from the storage device, When it is determined whether or not an error has occurred in the stored data, and when it is determined that an error has occurred, the process proceeds to step 8, the error of the stored data is corrected according to the error correction code, and then in step 9 that follows. The restored storage data is generated by universally decoding the corrected storage data, and in the subsequent step 10, the dictionary data is accumulated in synchronization with this universal decoding. On the other hand, if it is determined in step 7 that no error has occurred, the process immediately proceeds to step 9 to universally decode the stored data to generate restored data.

Then, in the following step 11, it is determined whether or not a restoration error has occurred during the universal decoding process. When it is determined that the restoration error does not occur, the process proceeds to step 12 and the final data to be restored. If it is the final data, the process is ended, and if it is not the final data, the process returns to step 7 to continue the read / correction process of the stored data and the generation process of the restored data. When it is determined in step 11 that a restoration error has occurred, the stored data in the storage device that is compressed unlike the communication system cannot be operated, so the processing is stopped as it is.

In this way, in the data compression / decompression process of the conventional storage system using the universal code, when a decompression error occurs on the decompression side, the process is stopped as it is.

[0034]

However, in the error control process of the data compression / decompression process in such a communication system, when a decompression error occurs, the compression side
Since the configuration is such that the encoding process is performed again from the beginning to generate the compressed data and the compressed data is retransmitted to the decompression side, as shown in FIG.
There is a problem that the data compression rate is significantly deteriorated when a restoration error occurs.

In the error control process of the conventional data compression / decompression process in such a storage system, there is a problem that when a decompression error occurs, the subsequent data cannot be decompressed.

The present invention has been made in view of the above circumstances, and in the data compression / decompression process according to the universal code, a new data compression / decompression for appropriately dealing with a case where an error occurs on the decompression side. The purpose is to provide an error control processing method in processing.

[0037]

FIG. 1 shows the principle configuration of the present invention. In the figure, 1 is a compression side apparatus including the present invention, which generates compressed data of data to be processed according to universal encoding processing, 2 is a decompression side apparatus including the present invention, which is a universal decoding A device for decompressing the compressed data generated by the compression side device 1 according to the processing, a communication path 3 for transferring the compressed data generated by the compression side device 1 to the decompression side device 2, and a storage device 4 The compressed data generated by the compression side device 1 is stored.

The compression side device 1 comprises an encoding means 10, an accumulating means 11, a period detecting means 12, an initializing means 13 and
The adding means 14 and the error handling means 15 are provided. The encoding means 10 accumulates the learning data in the accumulating means 11 and executes the universal encoding process of the data to be processed based on the learning data managed by the accumulating means 11.
The period detection unit 12 periodically performs the encoding process executed by the encoding unit 10 according to the number of pieces of processing target data input to the encoding unit 10 and the number of codes of compressed data output by the encoding unit 10. Detect the passage of a certain period. The initializing means 13 sets the learning data managed by the accumulating means 11 in a prescribed learning progressing state (a learning progressing state may not be reached at all) at regular intervals detected by the period detecting means 12.
Initialize to The adding means 14 is the period detecting means 1
The identification code is added to the compressed data output from the encoding means 14 at every constant period detected by the second method. Error handling means 15
Adds an error detection code capable of detecting an error in communication or an error correction code capable of correcting an error in storage to the compressed data output from the encoding means 14.

The restoration side device 2 includes a decryption means 20, an accumulation means 21, a period detection means 22, an initialization means 23, and
The error detection means 24, the error processing means 25, and the error handling means 26 are provided.

The decoding means 20 accumulates the learning data in the accumulating means 21, and executes the universal decoding process of the code to be processed based on the learning data managed by the accumulating means 21. When the period detecting unit 12 of the compression side device 1 detects the passage of a certain period according to the number of data to be processed, the period detecting unit 22 follows the same number of restored data output from the decoding unit 20, and When the period detection unit 12 detects the passage of a certain period according to the number of codes of the output compressed data, the period of the decoding process executed by the decoding unit 20 according to the same number of codes to be processed input to the decoding unit 20. A certain period of time is detected. The initializing means 23 initializes the learning data managed by the accumulating means 21 to the same learning progress state set by the initializing means 13 of the compression side device 1 at every constant period detected by the period detecting means 22. .

The error detecting means 24 is the period detecting means 22.
The error occurrence is detected by checking whether or not the identification code is added to the processing target code at every constant period detected by the period detection means 22.
Decoding means 20 using a fixed period detected by
Detects a restoration error that occurs in the decryption process executed by. When the error detection unit 24 detects an error occurrence, the error processing unit 25 sets the restored data of a certain fixed period as the restored data of the error occurrence period. The error handling means 26 detects an error in communication according to the error detection code added by the error handling means 15 of the compression side device 1, and corrects the error in storage according to the error correction code added by the error handling means 15. Or

[0042]

According to the present invention, in the compression side device 1, the period detection means 12 detects the passage of a periodic fixed period of the universal encoding process executed by the encoding means 10, and upon receiving this detection result, initialization is performed. The means 13 initializes the learning data managed by the accumulating means 11 at every detected fixed period. On the other hand, in the decompression-side device 1, the period detection means 22 synchronizes with the detection process of the period detection means 12 of the compression-side device 1 and the periodic fixed period of the universal decoding process executed by the decoding means 20 elapses. In response to the detection result, the initialization unit 23 receives the detection result every fixed period.
The learning data managed by the storage unit 21 is initialized.

In this way, the learning data of the storage means 11 of the compression side device 1 is increased from the initial registration value as shown in FIG. 2A, and when the period detection means 12 detects a certain period. Therefore, the data compression rate of the universal coding process executed by the coding means 10 is correspondingly changed to the mode shown in FIG. 2B. Will be shown. On the other hand, the learning data of the storage means 21 of the restoration side device 2 is also shown in FIG.
As shown in (a), the mode in which the value increases from the initial registration value and returns to the original initial registration value when the period detection means 22 detects a certain period is repeated.

In this processing, as shown in FIG. 5, the error processing means 25 of the restoration side device 2 restores the restored data output by the decoding means 20 and restores the restored data for a certain period before one time. If the error detecting means 24 does not detect the occurrence of an error by adopting a configuration of holding data and data at the same time,
The restored data output by the decoding means 20 is output in the same output order. That is, the error processing means 25
As shown in FIG. 3B, the restored data output by the decoding means 20 is processed so as to be output in the same output order. On the other hand, when the error detecting means 24 detects the occurrence of an error, the decoding means 20 interrupts the decoding processing as shown in FIG.
Replaces the restored data in the error occurrence period with the restored data in the adjacent fixed period and outputs the data. That is,
As shown in FIG. 4B, the error processing unit 25 replaces the restored data of the error occurrence period with the restored data of a certain period before, for example, and outputs it.

As described above, according to the present invention, the storage means 11,
The configuration is such that the learning data managed by 21 is initialized at regular intervals, and the universal encoding process and the corresponding universal decoding process are executed.
When an error (an error detected by an identification code or a restoration error) occurs on the restoration side, the restoration data in the error occurrence period is replaced with the restoration data in the adjacent fixed period. Even if an error occurs on the restoration side, the restoration data in the error occurrence period becomes approximate, but the restoration process can be continued as it is. Further, in the present invention, since the decompression side apparatus 2 adopts a configuration in which all error processing is executed, the data compression / decompression processing of the storage system is not limited to the error control processing of the data compression / decompression processing of the communication system.・
It can be directly applied to the error control processing of the restoration processing.

When the present invention is applied to the error control process of the data compression / decompression process of the communication system, the compressed data can be transferred at high speed while realizing the high data compression rate. When the present invention is applied to the error control process of the data compression / decompression process of the storage system, even if a decompression error occurs, all the data can be decompressed.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. FIG. 6 shows an embodiment of an error control processing flow of the data compression / decompression processing of the present invention in the communication system. Next, according to this processing flow, the error control processing of the data compression / decompression processing of the present invention in the communication system will be described in detail.

In the communication system of the present invention, the compression side device 1 described in FIG.
When it is initialized to the specified specified learning progress state, next, in step 2, the input data to be encoded is universally encoded to generate compressed data, and in step 3, the universal encoding is performed. The dictionary data is accumulated in synchronization with.

Subsequently, in step 4, it is judged whether or not the progress of the universal encoding process has reached a periodic fixed period, and when it is judged that the fixed period has been reached, the process proceeds to step 5, After adding an identification code indicating that fact, the generated compressed data is shown in FIG.
It is transmitted to the restoration-side apparatus 2 described in. On the other hand, when it is determined in step 4 that the fixed period has not been reached, the process directly proceeds to step 6 without executing the process of step 5, and the generated compressed data is transmitted to the decompression side device 2. At this time, in step 7, the error detection code is added, and if there is a retransmission request from the decompression side device 2 due to a communication error, the compressed data is retransmitted in response to the request.

Then, in the following step 8, it is judged whether or not it is the final data to be encoded, and if it is the final data, the process is terminated, and if it is not the final data, the process proceeds to step 9 to perform the universal encoding process. If it is determined that the progress has not reached the periodic fixed period, and if it has not reached the fixed period, the process returns to step 2 to continue the generation / transmission process of the compressed data. . On the other hand, when it is determined that the fixed period has been reached, the process returns to step 1 to initialize the dictionary data and then continue the compressed data generation / transmission process.

On the other hand, the restoration side device 2 is
When the dictionary data is initialized to the same learning progress state as the compression side device 1, next, in step 11, the compression side device 1
According to the error detection code added to the compressed data transmitted from, it is detected whether a communication error has occurred, and if an error has occurred, a resend request is issued. It should be noted that this resend process has a configuration in which both the compression side device 1 and the decompression side device 2 have a buffer memory, and data is retransmitted between the buffer memories. It does not affect the universal encoding process or the universal decoding process of the restoration-side apparatus 2.

Subsequently, in step 12, the compressed data transmitted from the compression side device 1 is received, and then in step 1
In 3, it is determined whether or not the progress of the universal decoding process has reached a certain period of the cycle, and when it is determined that the certain period has been reached, the process proceeds to step 14 to add the compression side device 1. It is determined whether the identification code exists. When it is determined in step 14 that the identification code exists, the process proceeds to step 15, the identification code is removed, and then the process returns to step 10 to initialize the dictionary data and then restore data of the next fixed period. Enter the generation process.

On the other hand, when it is determined in step 13 that the fixed period has not been reached, the process proceeds to step 16, where the compressed data received in step 12 is universally decoded to generate decompressed data, and the subsequent step 1
At 7, the dictionary data is accumulated in synchronization with this universal decoding. Then, in a succeeding step 18, it is determined whether or not a restoration error (for example, a restoration error such as a reference number that does not appear in the dictionary data) occurred during universal decoding, and it is determined that the restoration error does not occur. In some cases, the process proceeds to step 19, and it is determined whether or not it is the final data to be decompressed. If it is the final data, the process is ended, and if it is not the final data, the process returns to step 12 to perform the compressed data reception process. Continue the restoration data generation process.

On the other hand, when it is determined in step 14 that the identification code does not exist, it means that some kind of error has occurred. Therefore, the process proceeds to step 20, and the data which has been restored one time before is used as the restored data in the error occurrence period. After setting the decompressed data for the period, the process returns to step 10 to initialize the dictionary data, and then the decompression process of the compressed data is continued. Then, when it is determined in step 18 that a restoration error has occurred, the process also proceeds to step 20, and the restoration data of the previous fixed period is set as the restoration data of the error occurrence period, and then the step 10 Back to
Initialize the dictionary data and continue the compression data decompression process.

As described above, in the error control processing of the data compression / decompression processing according to the present invention, universal coding / decoding is performed.
When the universal encoding / decoding process is executed by adopting the configuration that the dictionary data accumulated by the decoding process is initialized at regular intervals, and if an error occurs on the restoration side, the error Since the restoration data in the occurrence period is replaced with the restoration data in the adjacent fixed period, even if an error occurs in the restoration device 2, the restoration data in the error occurrence period is approximate. However, the restoration process can be continued as it is. From now on, when the present invention is applied to a communication system,
Even if an error occurs in the restoration side device 2, the universal encoding / decoding process does not have to be redone from the beginning.

When the error control processing of the data compression / decompression processing according to the present invention is applied to the storage system, the compression side device 1
6 adopts a configuration in which the error correction code is added instead of the error detection code in step 7 of the processing flow of FIG. 6, and the processing flow of FIG. 6 is executed. In step 11 of the processing flow of the above, the process using the error correction code (the process of detecting an error in communication and the process of issuing a retransmission request based on it) is replaced with the process of using an error correction code (the occurrence of an error in memory). Detection process and correction process of stored data based on the detection process) and the process flow of FIG. 6 is executed.

As described above, the processing of the processing flow of FIG. 6 according to the present invention can be applied to the storage system as it is. From this, when the present invention is applied to the storage system, even if an error occurs in the restoration side device 2, the restoration data in the error occurrence period becomes approximate, but the restoration process can be continued as it is. Even if an error occurs in the restoration side device 2, all data can be restored.

7 to 9 show an embodiment of the processing flow when the processing flow of FIG. 6 is implemented according to the LZW code. Next, the processing flow of FIGS. 7 to 9 will be described in detail.

As shown in the processing flow of FIG. 7, the compression-side apparatus 1 firstly, at step 1, 256 of all single characters that may appear in the character string to be encoded.
Characters are registered in a dictionary together with reference numbers (“1” to “256”), “257” is set as an identification code, and T is set as the number of input characters used for detection for a certain period. next,
In step 2, the dictionary data is initialized. That is, N character strings ωK prepared in advance are added to the dictionary by adding reference numbers of “258” or less, “N + 1” is set to the leading address N of the dictionary, and “0” is set to the count value C of the input characters. "Set.

Then, in step 3, the first character K of the input data to be encoded is input, the reference number of the character K is set as the initial character string ω, and the count value C of the number of input characters is set. Is incremented by 1. Then, in step 4, the next character K is read from the input data to be encoded, and the count value C of the number of input characters is incremented by 1, and in the following step 5, the count value C of the number of input characters exceeds T. If it is determined that it has exceeded the threshold, the process proceeds to step 6, the reference number of the initial character string ω is output, and the identification code “25” is output.
After outputting "7", the process returns to step 2.

On the other hand, when it is determined in step 5 that C does not exceed T, the process proceeds to step 7 and a character string of a combination of the initial character string ω representing the reference number and the character K read in step 4 It is determined whether ωK is registered in the dictionary. When it is determined in step 7 that the character string ωK is registered in the dictionary, the process proceeds to step 8 and the reference number of the character string ωK is set to the new initial character string ω.
Then, in the following step 9, it is judged whether or not the processing has been completed for all the characters of the input data to be encoded. If it is judged that the processing has not been completed, return to step 4. When it is determined that the longest matching character string has been searched for, and the processing has ended, the process proceeds to step 11, the reference number of the initial character string ω is output, and the processing ends.

When it is determined in step 7 that the character string ωK is not registered in the dictionary, the initial character string ω
Corresponding to the longest matching character string,
Proceeding to step 10, the reference number of the initial character string ω is output, this character string ωK is added to the reference number and registered in the dictionary, and the reference number of the one character K following the initial character string ω up to that point. Is set as a new initial character string ω, the maximum value of the reference number is incremented by 1, and then the process proceeds to step 9 to start searching for the next longest matching character string. On the other hand, as shown in the process flow of FIG. 8, the restoration-side apparatus 2 firstly refers to all the 256 single characters that may appear in the restored character string in step 1 with reference numbers (“ 1 "to" 256 ") are registered in the dictionary," 257 "is set as an identification code, and T is set as the number of input characters used for detection in a certain period. Next, in step 2, the dictionary data is initialized. That is, N character strings ωK prepared in advance are added to the dictionary by adding reference numbers of “258” or less, and “N +” is added to the start address N of the dictionary.
1 "is set, and the count value C of the number of input characters is set to" 0 ".

Then, in step 3, the first code (CODE) of the input data (reference number string) to be restored is set and set as OLDcode, and the dictionary is searched to find the character pointed to by this CODE. Find K and output it.
Here, the output character K is char for later exception handling.
To set. Then, in step 4, the next code (CODE) is read from the input data to be restored and NEWc
Set as ode. Then, in step 5, it is checked whether or not the CODE read in step 4 is registered in the dictionary. If it is judged in this step 5 that CODE is registered in the dictionary, proceed to step 6
The character string ωK pointed to by DE is read from the dictionary, then in step 7, the character K of this character string ωK is stored in the stack, the reference number ω of this character string ωK is set as a new CODE, and the number of input characters is counted. The value C is incremented by 1, and the process returns to step 6.

When it is determined that CODE reaches the state of indicating one character by recursively executing the processing of steps 6 and 7, the process proceeds to step 8 and the character string stacked in step 7 is deleted. LILO (Last In Fast O
ut) format is popped up and output, and subsequently, in step 9 of the processing flow shown in FIG. 9, it is determined whether or not the count value C of the number of input characters has reached the set number T of input characters. If it is judged in step 9 that it has been reached, the process proceeds to step 10, where the next code (CODE) is read from the input data to be restored and set to SPcode, and in the following step 11, this SPcode is the identification code. Whether or not it matches “257” is determined. If they match, the process directly returns to step 2 of the processing flow of FIG. 8, and if they do not match,
Proceed to step 12, notify the error detection, read the code of the input data until the next identification code, replace the restored data of the error occurrence period with the restored data of the next fixed period, and output it, then return to step 2. To go.

On the other hand, when it is determined in step 9 that the count value C of the number of input characters does not reach the set number of input characters T, the process proceeds to step 13, and the previously used reference number ω set in the OLD code and the current reference number ω are set. The reference character is added to the character string ωK consisting of a combination with the first character of the restored character string, registered in the dictionary, and the first character of the restored character string is set to char for later exception processing, NEW code CODE
Is set as the OLD code, and the maximum value of the reference number is incremented by 1. And the following step 14
Then, it is judged whether or not the processing has been completed for all the codes of the input data to be restored, and when it is judged that the processing has not been completed, by returning to step 4 of the processing flow of FIG. The code restoration process is executed, and when it is determined that the process is finished, the process is finished.

When it is determined in step 5 that the CODE read in step 4 is not registered in the dictionary, the process proceeds to step 15 and the following exception processing is executed. That is, char is output, OLDcode is set as CODE, and the combination of OLDcode and char is NEW.
The code is set, and the process proceeds to step 6.

In the embodiment of the processing flow shown in FIGS. 7 to 9 described above, the compression side apparatus 1 determines the initialization processing timing of the dictionary data according to the number of data (the number of characters) of the input data to be processed. Together with the restoration side device 2
Discloses a configuration for determining the initialization processing timing of dictionary data in accordance with the number of restored data (the number of characters) of the restored data. However, the compression side device 1 initializes the dictionary data according to the code number of the compressed data to be output. It is also possible to adopt a configuration in which the restoration side device 2 determines the initialization processing timing of the dictionary data in accordance with the code number of the input processing target code while determining the timing. 10 to 12 show an example of the processing flow in the case of following this configuration.

As described above, according to the present invention, the universal encoding / decoding process is executed by adopting a configuration in which the dictionary data accumulated by the universal encoding / decoding process is initialized at regular intervals. At the same time, when an error occurs on the restoration side, the restoration data in the error occurrence period is replaced with the restoration data in the adjacent fixed period.

Although the illustrated embodiment has been described, the present invention is not limited to this. For example, in the embodiment,
Although the present invention has been disclosed according to the LZW code, the present invention is not limited to this and can be applied as it is to a code using another universal code such as an arithmetic code. Further, in the embodiment, as the restoration data of the error occurrence period,
Although the present invention has been disclosed by using the restored data for a certain period before that, the present invention is not limited to this, and the restored data for a certain period after that may be used.
Then, in the embodiment, the present invention has been disclosed by initializing the dictionary data to include a character other than a single character. However, the present invention is not limited to this, and the data including only a single character is initialized. May be.

[0070]

As described above, according to the present invention,
In the data compression / decompression process according to the universal code, even if an error occurs on the decompression side, the decompression data in the error occurrence period becomes approximate, but the decompression process can be continued as it is. Moreover, this effect can be obtained only by the decompression side without making any request to the compression side. From this, the present invention is not only a communication system,
It can be applied to the storage system as it is, and when applied to the communication system, even if an error occurs on the restoration side, the universal encoding / decoding process does not have to be redone from the beginning. Moreover, if it is applied to a storage system, even if an error occurs on the restoration side, all data can be restored.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is an explanatory diagram of processing of the present invention.

FIG. 3 is an explanatory diagram of a process of the present invention.

FIG. 4 is an explanatory diagram of processing of the present invention.

FIG. 5 is a configuration example of an error processing unit.

FIG. 6 is an example of the present invention in a communication system.

FIG. 7 is an embodiment of the present invention using LZW codes.

FIG. 8 is an embodiment of the present invention using LZW codes.

FIG. 9 is an embodiment of the present invention using LZW codes.

FIG. 10 is an embodiment of the present invention using LZW codes.

FIG. 11 is an embodiment of the present invention using an LZW code.

FIG. 12 is an embodiment of the present invention using LZW codes.

FIG. 13 is an explanatory diagram of a data encoding process using an LZW code.

FIG. 14 is an explanatory diagram of data restoration processing using LZW code.

FIG. 15 is an explanatory diagram of a dictionary registration configuration in LZW code.

FIG. 16 is an explanatory diagram of a data encoding process using an LZW code.

FIG. 17 is an explanatory diagram of data restoration processing using LZW code.

FIG. 18 is an explanatory diagram of a conventional technique in a communication system.

FIG. 19 is an explanatory diagram of a conventional technique in a communication system.

FIG. 20 is an explanatory diagram of a conventional technique in a storage system.

FIG. 21 is an explanatory diagram of a conventional technique in a storage system.

FIG. 22 is an explanatory diagram of a problem of the conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 compression side device 2 decompression side device 3 communication path 4 storage device 10 encoding means 11 storage means 12 period detection means 13 initialization means 14 addition means 15 error handling means 20 decoding means 21 storage means 22 period detection means 23 initialization Means 24 Error detecting means 25 Error processing means 26 Error handling means

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hirotaka Chiba 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited

Claims (5)

(57) [Claims] 1. An error control processing method in data compression / decompression processing, wherein the compression side stores learning data in a storage means (11),
Encoding means (10) for executing universal encoding processing of data to be processed based on learning data managed by the accumulating means (11), and periodical encoding processing executed by the encoding means (10) Period detecting means (12) for detecting the passage of a fixed period, and the accumulating means for each fixed period detected by the period detecting means (12).
Initializing means for initializing the learning data managed by (11) (13)
And an addition means (14) for adding an identification code to the compressed data output from the encoding means (10) at regular intervals detected by the period detection means (12). Decoding means (20) for accumulating learning data in the accumulating means (21) and executing universal decoding processing of the code to be processed based on the learning data managed by the accumulating means (21), and the decoding means Period detection means (2) for detecting the elapse of the certain period of the periodic decoding process executed by the means (20)
2), the initialization means (23) for initializing the learning data managed by the storage means (21), and the period detection means (22) at regular intervals detected by the period detection means (22). An error detection means (24) for detecting an error occurrence by checking whether or not the identification code is added to the processing target code at every fixed period to be detected, and the error detection means (24) detects the error occurrence Error processing means (25) for setting the restoration data of a certain fixed period as the restoration data of the error occurrence period
An error control processing method in data compression / decompression processing characterized by comprising: 2. The error control processing method in the data compression / decompression processing according to claim 1, wherein the error detection means (24) uses the fixed period detected by the period detection means (22) as a detection unit, and the decoding means (24). An error control processing method in data compression / decompression processing, which is characterized in that it also performs processing to detect an error that occurs in the decoding processing executed in 20). 3. The error control processing method in the data compression / decompression processing according to claim 1 or 2, wherein the compression side period detecting means (12) is data of processing target data input to the encoding means (10). Detecting the passage of a certain period of encoding processing according to the number, and detecting the period on the restoration side
(22) is an error control processing method in data compression / decompression processing, characterized in that processing is performed so as to detect elapse of a certain period of decoding processing according to the number of pieces of decompressed data output from the decoding means (20). 4. The error control processing method in the data compression / decompression processing according to claim 1 or 2, wherein the compression-side period detection means (12) is in accordance with the code number of the compressed data output from the encoding means (10). While detecting the passage of a certain period of the encoding process, the period detection means (22) on the restoration side,
An error control processing method in data compression / decompression processing, characterized in that processing is performed so as to detect elapse of a certain period of decoding processing according to the number of codes to be processed input to the decoding means (20). 5. The error control processing method in the data compression / decompression process according to claim 1 or 2, wherein the compression side and decompression side initialization means (13, 23) are storage means (1).
An error control processing method in data compression / decompression processing, characterized in that the learning data managed by 1,21) is processed to be initialized to a specified learning progress state.