KR100244766B1 - Improving modem coder and decoder - Google Patents

Abstract

The present invention performs continuous generation and update of codewords through string matching between input digital data and code table at the transmitting side, compresses and encodes input digital data using the generated and updated codeword, and receives at receiving side. The present invention relates to a system capable of restoring an encoded code data through a string matching to an original signal before encoding. And a basic code of 1 are respectively registered at predetermined addresses of the transmitting side code table, and the basic code registers new codewords having a bit length at least larger than the basic code and obtained by performing string matching between an n-bit input symbol and the code table. Register sequentially to the address after the received address, and The mask bit section of the n-bit digital data to be input is determined, and the registered codeword provided in the transmission code table and the remaining input bit values except the least significant bit of the n-bit input digital data determined by the mask bit section. Perform matching between the two, and extract n-bit codeword index information having a variable length corresponding to the remaining input bit value as a result of the matching and transmit the same to the transport channel; The receiver performs string matching of the remaining bit values except the least significant bit among the n bits of code data received through the transmission channel, and restores the m bits of codewords corresponding to the n bits of input code data. The base code is sequentially registered to the address of the registered reception code table, the detection code information of n bits included in the code bitstream is detected, and n provided for restoring to the original signal based on the detected recognition code information. The mask bit section of the bit input code data is determined, and the matching between the n bit input code data determined according to the mask determination signal and the registered codewords provided in the reception code table is performed. The codeword registered at the corresponding index is output as the reconstruction data of the input code data.

Description

Improved Modem Encoding and Decoding System

The present invention relates to a coding and decoding technique for a modem, and more particularly, to an improved coding and decoding system for a modem suitable for application to the Lempel-Ziv coding (LZC) algorithm defined in CCITT V.42 bis. And a code / decoding method thereof.

As is well known, the transmission of digital signals can deliver higher quality video images than the transmission of analog signals. However, when an image signal including a series of image frames is represented in digital form, it generates relatively more data than an analog signal.

Therefore, since a valid frequency band is limited in a communication modem transmitting digital data, data to be transmitted using a compression method such as variable length coding or fixed length coding is used to transmit a desired amount of data through a limited channel width. Compression coding.

In this case, variable length coding compresses data by assigning a short length code to relatively frequent symbols and a long length code to low frequency symbols. Compressed data is assigned by assigning fixed length symbols to symbols.

Meanwhile, when performing variable length encoding or fixed length encoding, a codeword corresponding to an input symbol is searched for in a code table prepared through string matching, and a corresponding codeword index is transmitted. It can be said that string matching between tables is determined.

At this time, in the conventional method, string matching between the input data and the code table is performed continuously by receiving one symbol, and even after such a string process is performed, the string matching is performed by one symbol after a certain amount of time. It is a cause to reduce.

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art, and performs generation and update of codewords continuously through string matching between input digital data and code table in a transmitting modem, and uses generated and updated codewords. It is an object of the present invention to provide a coding system for a modem capable of compressing and encoding input digital data.

Another object of the present invention is to provide a decoding system capable of reconstructing code data provided according to an encoding system of the present invention to an original signal before encoding while generating codewords through string matching.

In accordance with an aspect of the present invention, there is provided a coding system for a modem which compresses and encodes digital data by using string matching between input digital data in a bitstream form and codewords in a code table. Is a memory for initially storing codeword index allocation bit conversion recognition codes, 0 and 1 basic codes, respectively, at predetermined addresses, and storing conversion data obtained by converting an analog signal into a digital signal for encoding; Sequentially registering new codewords having a bit length greater than the base code and obtained by performing string matching between an n-bit input symbol provided from the memory and a code table at an address after the base code is registered; A string matching block for generating a mask determination signal for determining a bit section of n-bit input digital data provided from said memory for encoding; When the n-bit codewords generated through the string matching are registered, the code table is searched to check whether all codewords having the same n-bit length are registered, and the specific code having the same n-bit length is checked. A codeword registration determination block for generating a specific codeword registration completion signal when it is determined that all of the words are registered; When the specific codeword registration completion signal is received from the codeword registration determination block, a clear decision signal for clearing codewords having n-2 bit lengths is generated to be registered at the n- address of the code table. An update decision block for deleting codewords having a 2-bit length; And matching the remaining input bit values except the least significant bit among the n bit input digital data determined according to the mask determination signal provided from the string matching block with the registered codewords provided in the code table. As a result of the matching, n-bit codeword index information having a variable length corresponding to the remaining input bit values is extracted and transmitted to a transport channel, and codeword index information extraction is performed through matching between the remaining input bit values and the registered codeword. Provides an improved encoding system for a modem consisting of an encoding block that is performed in parallel with the generation registration of a codeword corresponding to the input data.

According to another aspect of the present invention, a string matching between code data in a code bitstream and codewords in a code table is input. In the modem decoding system for restoring the input code data to the original signal before encoding, the code table stores the input code data received through a transmission channel, in which a basic code of 0 and 1 is registered at a predetermined address, respectively. Memory; M-bit codeword corresponding to the n-bit input code data is restored by performing string matching of the remaining bit values except the least significant bit among the n-bit code data provided from the memory and having a bit length greater than that of the basic code. Register the reconstructed codewords sequentially at an address after the base code is registered, detect the n-bit recognition code information included in the code bitstream, and based on the detected recognition code information. A string matching block for generating a mask determination signal for determining a bit section of n-bit input code data provided from the memory for restoration to an original signal; When the m-bit codewords generated through the string matching are registered, the code table is searched to check whether all codewords having the same n-bit length are registered, and the specific code having the same n-bit length is checked. When it is determined that all of the words are registered, a clear decision signal for clearing codewords having an n-2 bit length is generated to delete the codewords having the n-2 bit length registered at a predetermined address of the code table. Update decision block; And performing matching between the n-bit input code data determined according to the mask determination signal provided from the string matching block and the registered codewords provided in the code table, and matching the input code data. The codeword registered in the index is output as reconstruction data of the input code data, and the data reconstruction through matching between the input code data and the registered codeword is performed in parallel with the generation registration of the codeword corresponding to the input code data. Provided is an improved decoding system for a modem consisting of decoding blocks to perform.

1 is a block diagram of an improved coding system for a modem according to a preferred embodiment of the present invention;

2A illustrates an example of a bitstream input for encoding;

2B illustrates an example of a code table generated according to an input bitstream;

3 is a block diagram of an improved decoding system for a modem according to a preferred embodiment of the present invention;

4 illustrates an example of data restored through string matching in accordance with the present invention.

<Description of the code | symbol about the principal part of drawing>

102,302: Memory 104,304: String Matching Block

106306: Code table 108: Codeword registration decision block

110,308: update decision block 112: encoding block

310: decoding block

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a coding system for a modem according to a preferred embodiment of the present invention.

As shown in the figure, the encoding system of the present invention comprises a memory 102, a string matching block 104, a code table 106, a codeword registration decision block 108, an update decision block 110 and an encoding block. (112).

Referring to FIG. 1, the memory 102 stores input data to be encoded as a frame memory, for example, the digital data stored therein is a string matching block 104 and an encoding block 112 through a line L11. Is passed to each.

Next, the string matching block 104 continuously generates a codeword of a predetermined length to be registered in the code table 106 through string matching between the input data and the code table 106 using the pointer P. The n-bit codewords generated here are registered at predetermined addresses of the code table 106, respectively.

Also, the string matching block 104 generates and encodes a mask control signal MS on a line L12 that determines a mask section of input data to be divided for encoding at the time of encoding the input data in the encoding block 112 described later. To block 112.

As an example, a step up codeword having a value of "0" at address 0 is registered, as shown in FIG. 2B, and the encoding system is initialized. In the state where the codeword value of the address is registered as "0" and "1"), the input data is "0, 1, 0, 0, 1, 1, 0, 0, 1, 1, Assuming 1, ---- ", the string matching block 104 checks whether the symbol" 01 "is registered in the code table 106 because the symbols" 0 "and" 1 "are already registered. As a result of the check, since the value of "01" is not registered, the codeword value of "01" is registered at address 3, and the pointer P moves to the symbol position of "1". At this time, the encoding block 112 described later transmits the index code "01" of the symbol "0". Subsequently, it is checked whether or not the next symbol "10" is registered, and a code value of "10" is registered at address 4, and the pointer P moves to the symbol position of "0". At this time, the encoding block 112 transmits the step-up code code "00" for recognizing the code index allocation bit conversion, and then transmits the index code "010" of the symbol "1".

As described above, the next symbol "00" is registered at address 5, the index code "001" of symbol "0" is transmitted, and the pointer P is moved to check the next symbol. At this time, since the next symbol "01" following the symbol "00" is already registered at address 3, check the "011" which is up to the next one bit and register it at the address 6, and at the same time, the index code of the symbol "01" Send "011" and move the pointer P to check the next symbol. Similarly, the next symbol "10" following "011" is already registered at address 4, so check "100", which is the next one bit, and register it at address 7, and at the same time, the index code of symbol "10" Send 100 ”.

In addition, since the next symbol "001" following the symbol "100" is already registered at address 6, check "0111", which is up to the next next bit, is registered in address 8. At this time, the encoding block 112 described later transmits the step-up code code "000" for recognizing the code index allocation bit conversion, and then transmits the index code "0110" of the symbol "011".

Therefore, the string matching block 104 checks whether the corresponding symbol is registered while moving the pointer P through the above-described process, and based on the check result, new codes not registered are added to the code table 106. The code is registered at a predetermined address, and a continuous code registration or registration update to the code table 106 is performed through this process.

Meanwhile, in the codeword registration determination block 108, when the registration of codes is performed in the code table 106 through the above-described process, the codeword 106 is searched to register all the codewords for a specific bit length. Check whether all four 2-bit codewords are registered, and when the registration of the 2-bit codewords is completed, the eight 3-bit codewords are again checked for complete registration. If it is determined whether registration is complete or not, and if it is determined that the registration of the 2-bit codeword is completed, a registration completion signal is generated on the line L15 and provided to the update decision block 110.

Next, the update decision block 110 generates a clear decision signal for updating the codeword registered in the code table 106 and provides it to the code table 106 via the line L16. For example, in FIG. As shown, when a 2-bit codewords are all registered (generated) and string matching for 3-bit codeword generation is performed, a clear decision signal for clearing the pre-registered 1-bit codewords is provided on the line L16. Occurs.

Therefore, in the code table 106, all 2-bit codewords registered at addresses 1 and 2 are cleared, and the addresses thus cleared are again registered at the next codewords (i.e., 4-bit or more codewords). Will be used. This is, after all, to minimize the memory capacity for the code table. Therefore, after a string matching process for a predetermined time, the code table 106 will be filled with codewords having a predetermined bit length (eg, 8 bits, 10 bits, etc.).

On the other hand, the encoding block 112 sets a section of the input data to be encoded according to the mask section setting signal provided from the string matching block 104 through the line L12, and input data included in the set mask section. The codeword index information corresponding to the codewords provided in the code table 106 is transmitted through a line L13, and are transmitted to the transport channel, not shown. For example, if the symbol of the mask section is "01", the index code "01" of the symbol "0" is transmitted. If the symbol of the mask section is "10", the step-up code code "00" for code index allocation bit conversion recognition is transmitted. Then, the index code corresponding to each symbol is transmitted by transmitting the index code "010" of symbol "1".

In this case, the encoding block 112 transmits codeword index information as fixed variable length information, for example, codeword index information of addresses 1, 2, and 3 is allocated as 2 bits, and transmitted. The codeword index information is allocated by 3 bits and transmitted, and the codeword index information of 8 to 15 is allocated by 4 bits and transmitted in such a manner that the codeword index information is transmitted by assigning a fixed variable length, thereby encoding efficiency. Further promote.

To this end, the encoding block 112 of the code table 106 prior to sending the initial three-bit codeword index information that occurs when the amount of bits allocated to the codeword index information is changed, that is, the first time when converting from 2 bits to 3 bits The step-up code (i.e., code recognizable by the decoder) previously registered at address 0 (for example, "00", "000", etc.) is transmitted first. Therefore, the decoding system side will recognize the allocation bit conversion of the index information through the reception of such a control code.

For example, when the input data on the line L11 is as shown in FIG. 2A and the codeword registered accordingly is as shown in FIG. 2B, the transport bitstream of the codeword indices output in the encoding block 112 is " 01 00 010 001 011 100 000 0110---- Here, the underlined 00 and 000 are step-up codes for codeword index allocation bit conversion recognition, and this step-up code is a kind of recognition code that is first sent to the previous bit length value every time the allocation bit is increased by one bit. to be.

Next, as described above, a process of restoring the encoded bitstream encoded according to the encoding system of the present invention and then received through the transport channel to the original signal (that is, the recovered digital data) before encoding will be described in detail.

3 shows a block diagram of an improved modem decoding system according to a preferred embodiment of the present invention. As shown in the figure, the decoding system of the present invention includes a memory 302, a string matching block 304, a code table 306, an update decision block 308, and a decoding block 310.

First, in the string matching block 304, the coded input data (i.e., index information including the identification code) and the code provided from the memory (e.g., the frame memory) 302 of the input side using the pointer P are coded. Through string matching between the tables 306, codes of a predetermined length that are to be registered in the code table 306 are continuously generated, and the n-bit codes generated therein are registered at predetermined addresses of the code table 306, respectively. .

In addition, the string matching block 304 lines a mask control signal MS for determining a mask section of input data to be divided for reconstruction at the time of decoding (ie, reconstructing) the input data in the decoding block 310 to be described later. Each time a step-up code (recognition code) which is generated and provided to the decoding block 310, i.e., index allocation bit conversion, is detected, a control signal for mask section setting is generated on the line L32.

At this time, the code table 306 in the decoding system has the same initialization state as the code table 106 in the encoding system described above, that is, as shown in FIG. 2B, the step-up has a value of "0" at address 0. (step up) Codewords are registered and codeword values of address 1 and address 2 are registered as "0" and "1", respectively.

Accordingly, in the string matching block 304, assuming that code data as shown in FIG. 4 is received through a transmission channel not shown, as an example, "0" which is a string of two bits of input code "01" Since it is already registered, the following input code is accepted. At this time, the decoding block 310 to be described later restores the data "0" corresponding to the address of the input code "01", where the pointer P is located at "0". Subsequent input code "00" is a step-up code for code index allocation bit conversion recognition, discards it, receives the next 3 bits input code, and generates a mask section setting signal on line L32. Therefore, the decoding block 310 also discards the step-up code for recognizing the code index allocation bit conversion in response to the mask period setting signal on the line L32 and subsequently receives an input code of 1 bit incremented by 3 bits.

Similarly, since "01", which is the string of the next input code "010", is not registered on the code table 306, it is registered at address 3, and data "1" corresponding to the address of the input code "010" is restored. The position of pointer P moves to “1” (0 1: where _ is the position of pointer P). Further, "0", which is a string of the following input code "001" address, is restored and string matching is performed to register "10" at address 4, and then move the pointer P to "0" (0 1 0).

Next, restore the string "01" of the input code "011" address, perform string matching, register "00" at address 5, and then move the pointer P to "0" (0 1 0 0 1) do. Also, restore the string "10" of the input code "100" address, perform string matching, register "011" at address 6, and move the pointer P to "1" (0 1 0 0 1 1 0 )do.

Again, since the next input code "000" is a step-up code for code index allocation bit conversion recognition, it is discarded and the next four bits of input code are accepted and the mask section setting signal is generated on the line L32. Therefore, the decoding block 310 also discards the step-up code for recognizing the code index allocation bit conversion in response to the mask period setting signal on the line L32 and subsequently receives an input code of 1 bit incremented by 4 bits.

Therefore, restore the string "011" of the next input code "0110" address, perform string matching, register "100" at address 7, and then move the pointer P to "0" (0 1 0 0 1 1 0 0 1 1).

That is, the same codes as those registered in the code table 106 of the above-described encoding system are registered or registered in the code table 306 through the above-described process, and the registered code information is restored when the input code data is restored. Is provided to decoding block 310 via line L35.

Meanwhile, in the update decision block 308, when the registration of codes for decoding is performed through the above-described process, the code table 106 is searched to check whether all codewords for a specific bit length are registered. In other words, it is checked whether all four 2-bit codewords are registered, and when the registration of the 2-bit codeword is completed, the complete registration of the specific bit length is checked by checking whether or not the eight 3-bit codewords are fully registered again. As a result of the check, as an example, when a 2-bit codeword is registered (generated) and string matching for 3-bit codeword generation is performed, a clear decision signal for clearing the pre-registered 1-bit codeword is line L34. Codewords registered at addresses 1 and 2 of the code table 306 will be cleared.

Therefore, when the above-described string matching process passes a predetermined time, the code table 306 has a predetermined bit length (for example, 8 bits and 10 bits) having the same value as that of the transmitting code table 106 shown in FIG. Codewords) will be filled.

On the other hand, the decoding block 310 sets the section of the input code (index information including the identification code) to be restored according to the mask section setting signal provided from the string matching block 304 through the line L32, By converting the input code (index information) to the corresponding codeword, that is, digital data, through matching between the input code included in the set mask period and the codewords provided in the code table 306 through the line L35, The original signal will be restored.

That is, assuming that code data of "01 00 010 001 011 100 000 0110----" is input as described above, the decoding block 310 discards the values "00" and "000", which are step-up codes. Then, the recovered digital data of "0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1, ----" corresponding to the remaining sign information will be output.

As described above, according to the present invention, the transmission modem performs continuous generation and update of codewords through string matching between input digital data and code table, and input / output digital data is generated using the updated / generated codeword. By encoding and coding the codeword index information having a variable length, the coding efficiency of digital data can be further improved.

Further, according to the present invention, the receiving side code used to restore the code data on the receiving side based on the data obtained as a result of performing the code encoding while registering and updating the codeword based on the input data, that is, the received code data. By generating the codewords registered in the table in the same way as the code table on the transmitting side, the code information encoded with the variable length can be effectively restored to the original signal before encoding.

Claims (8)

A coding system for a modem that compresses and encodes digital data by using string matching between input digital data in a bitstream form and codewords in a code table. In the code table, a codeword index allocation bit conversion recognition code and a base code of 0 and 1 are respectively registered at predetermined addresses, A memory for storing converted data obtained by converting an analog signal into a digital signal for encoding; Sequentially registering new codewords having a bit length greater than the base code and obtained by performing string matching between an n-bit input symbol provided from the memory and a code table at an address after the base code is registered; A string matching block for generating a mask determination signal for determining a bit section of n-bit input digital data provided from said memory for encoding; When the n-bit codewords generated through the string matching are registered, the code table is searched to check whether all codewords having the same n-bit length are registered, and the specific code having the same n-bit length is checked. A codeword registration determination block for generating a specific codeword registration completion signal when it is determined that all of the words are registered; When the specific codeword registration completion signal is received from the codeword registration determination block, a clear decision signal for clearing codewords having n-2 bit lengths is generated to be registered at the n- address of the code table. An update decision block for deleting codewords having a 2-bit length; And Performing matching between the remaining input bit values except the least significant bit among the n bits of input digital data determined according to the mask determination signal provided from the string matching block and the registered codewords provided in the code table, and matching As a result, the n-bit codeword index information having a variable length corresponding to the remaining input bit values is extracted and transmitted to the transport channel, and the codeword index information extraction through matching between the remaining input bit values and the registered codeword is performed. An improved modem coding system, comprising an encoding block that is performed in parallel with the generation registration of a codeword corresponding to the input data. 2. The improved encoding system of claim 1, wherein the addresses at which the registered codewords are deleted are reassigned to addresses of other codewords that are subsequently generated. The method according to claim 1 or 2, wherein the encoding block generates a corresponding step-up code using the recognition code whenever the bit value allocated to the codeword index information is increased by one bit. And transmitting the generated step-up code prior to transmitting the number of increased codeword index information. 4. The improved coding system for a modem according to claim 3, wherein the generated step-up code has the same number of bits as the codeword index information generated immediately before. Codeword Index Assignment Modem for reconstructing the input code data to the original signal before encoding using string matching between code data input in the form of code bit stream including recognition code for bit conversion recognition and codewords in code table In the decoding system, In the code table, 0 and 1 basic codes are registered at predetermined addresses, respectively. A memory for storing the input code data received via a transport channel; M-bit codeword corresponding to the n-bit input code data is restored by performing string matching of the remaining bit values except the least significant bit among the n-bit code data provided from the memory and having a bit length greater than that of the basic code. Register the reconstructed codewords sequentially at an address after the base code is registered, detect the n-bit recognition code information included in the code bitstream, and based on the detected recognition code information. A string matching block for generating a mask determination signal for determining a bit section of n-bit input code data provided from the memory for restoration to an original signal; When the m-bit codewords generated through the string matching are registered, the code table is searched to check whether all codewords having the same n-bit length are registered, and the specific code having the same n-bit length is checked. When it is determined that all of the words are registered, a clear decision signal for clearing codewords having an n-2 bit length is generated to delete the codewords having the n-2 bit length registered at a predetermined address of the code table. Update decision block; And Performing matching between the n-bit input code data determined according to the mask determination signal provided from the string matching block and the registered codewords provided in the code table, and a matching index corresponds to the input code data. Outputs the codeword registered in the data as reconstruction data of the input code data, and data reconstruction through matching between the input code data and the registered codeword is performed in parallel with the generation registration of the codeword corresponding to the input code data. Improved decoding system for a modem consisting of a decoding block. 5. The improved decoding system of claim 4, wherein the addresses at which the registered codewords are deleted are reassigned to addresses of other codewords that are subsequently generated. 6. The decoding block according to claim 4 or 5, wherein the decoding block removes n-bit recognition codes included in code data provided from the memory whenever the mask determination signal is provided from the string matching block, and restores data. Improved decoding system for a modem, characterized in that for increasing the bit interval by one bit. 7. The improved decoding system of claim 6, wherein the identification code has the same number of bits as the code data just recovered.

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