A variable-length encoder using a code table having a symbol/code-word re-association feature, which includes a first storing portion for storing previously generated code table information, a first re-associating portion for generating re-associated code table information and re-association information indicative of the relation between a symbol and a corresponding code word from a previously generated code table information stored in the first storing portion, based on the frequency of occurrence of externally applied symbols during a predetermined time period, a delay for delaying and outputting the same symbols as those input to the first re-associating portion during the predetermined time period, a re-association information storing portion for storing the re-associated code table information and re-association information and sequentially outputting the re-association information, a variable-length encoder for receiving the symbols stored in the delay and generating and sequentially outputting code words according to the re-associated code table information stored in the re-association information storing portion, and a multiplexer which outputs the re-association information from the re-association information storing portion and the code words output from the variable-length encoder, to thereby reduce the code length of code words generated by variable-length encoding even when the frequency of occurrence of symbols used in forming a previously generated code table is different from that of the symbols applied during the predetermined time period.
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0. 61. A variable-length decoding method, comprising:
receiving interleaved adapted association information and code word data; decoding said received code word using a code book, having a different association of code words and symbol data as compared to a previously used code book, in accordance with said adapted association indication information; and outputting said decoded code word data.
0. 43. A variable-length decoding method, comprising:
receiving interleaved adapted association information and code word data; generating a current code book, having a different association of code words and symbol data as compared to a previously generated code book, in accordance with said adapted information; and decoding said received code word data using said current code book and outputting decoded data.
0. 49. A variable-length decoding method, comprising:
receiving interleaved adapted association information and code word data; generating a current code book, having a different association of code words and symbol data as compared to a previously generated code book, in accordance with said adapted association information; and decoding said received code word data using said current code book and outputting decoded data.
30. A variable-length decoding method, comprising:
receiving interleaved re-association information and code word data and separating said re-association information and said code word data; generating a re-associated code book by modifying association of code words and symbol data as defined in a previously generated code book using said re-association information; and decoding said received code word data using said re-associated code book and outputting decoded data.
1. A variable-length code word transmission system, comprising:
encoder means for receiving and encoding input symbols into variable-length code words based on a frequency of occurrence of said symbols, said encoder means including means for re-associating a relationship between code words and each distinct received symbol and generating re-association information for each distinct received symbol; and means for transmitting said re-association information generated by said means for re-associating and said variable-length code words in an alternating manner; and decoder means for decoding the transmitted variable-length code words based on said transmitted re-association information. 26. A variable-length encoding method, comprising:
receiving input data; delaying the received input data for a pre-determined time period; counting occurrences of each distinct input data using the delayed input data; re-associating a relationship between code words and each distinct received input data based on the counted occurrence of each distinct input data, and generating re-association information for each distinct received input data, wherein the code words are read from a previously generated code book; encoding said received input data using the re-associated relationship and outputting selected code words; and transmitting said re-association information and the selected code words in an alternating manner.
0. 37. A variable-length encoding method, comprising:
receiving input symbol data; adapting a relationship between each distinct received input symbol data and variable-length code words and generating adapted association information for each distinct received input symbol data; generating a current code book, having a different association of code words and symbol data as compared to a previously generated code book, in accordance with said adapted association information; variable length coding said input symbol data into variable length code words using said current code book to generate variable length code words; and transmitting said adapted association information and said variable length code words in an alternating manner.
0. 55. A variable-length encoding method, comprising:
receiving input symbol data; adapting a relationship between each distinct received input symbol data and variable-length code words and generating adapted association information for each distinct received input symbol data, wherein the adapted association information for a code word is received only when the code word data is received for the first time during a predetermined time interval and before another code word data is received; encoding said received input symbol data using a current code book, having a different association of code words and symbol data as compared to a previously used code book, in accordance with said adapted association information, to generate variable length code words; and transmitting said adapted association information and said variable length code words in an alternating manner.
36. A digital data transmission method, comprising:
receiving input data; delaying the received input data for a pre-determined time period; counting occurrences of each distinct input data using the delayed input data; re-associating a relationship between code words and each distinct received input data based on the counted occurrence of each distinct input data, and generating re-association information for each distinct received input data, wherein the code words are read from a previously generated code book; encoding said received input data using the re-associated relationship and outputting selected code words; transmitting said re-association information and the selected code words in an alternating manner; receiving the re-association information and code word data and separating said re-association information and said code word data; generating a re-associated code book by modifying associations of code words and symbol data as defined in a previously generated code book using said re-association information; and decoding said received code word data using said re-associated code book and outputting decoded data.
18. A variable-length decoder for decoding output from a variable-length encoder using symbol/code-word re-association of a code table, the encoder having a previously generated code table stored in a code table, and which outputs data including code words and symbol/code-word re-association information, the decoder comprising:
storing means for storing the same code table as that previously generated and stored in the variable-length encoder; demultiplexing means for receiving data output from the variable-length encoder, and dividing and outputting symbol/code-word re-association information and code words from the received data, wherein the symbol/code word re-association information for one of the code words is received only when the code word is received for the first time during a predetermined time interval and before another code word is received; re-associating means for receiving said re-association information from said demultiplexing means, re-associating a code-word and a corresponding symbol, and storing said re-associated code table information; and variable-length decoding means for decoding the code words based on said code table information stored in said re-associating means to thereby generate a symbol.
23. A variable-length decoder for decoding output from a variable-length encoder using symbol/code-word re-association of a code table, the encoder having a previously generated code table stored in a code table, and which outputs data including code words and symbol/code-word re-association information, the decoder comprising:
storing means for storing the same code table as that previously generated and stored in the variable-length encoder; demultiplexing means for receiving data output from the variable-length encoder, and dividing and outputting symbol/code-word re-association information and code words from the received data, wherein said code words and said symbol/code-word re-association information are received in an alternating manner, and symbol/code-word re-association information for any one of the code words is received before said code words are received; re-associating means for receiving said re-association information from said demultiplexing means, re-associating a code word and a corresponding symbol when said code word is first received, and storing said re-associated code table information; and variable-length decoding means for decoding the code word based on the code table information stored in said re-associating means to thereby generate a symbol.
7. A variable-length encoder using symbol/code-word re-association of a code table comprising:
delay means for delaying externally applied symbols; first storing means for storing a previously generated code table; first re-associating means for generating a re-associated code table and re-association information indicative of the relation between one of said symbols and a corresponding code word from said previously generated code table stored in said first storing means, based on a frequency of occurrence of the externally applied symbols during a predetermined time period, wherein said first re-associating means generates re-association information for each different one of the externally applied symbols; re-association information storing means for storing said re-associated code table and said re-association information, and sequentially outputting said re-association information; variable-length encoding means for receiving the delayed symbols and generating and sequentially outputting code words according to said re-associated code table stored in said re-association information storing means; and means for multiplexing and outputting said re-association information output from said re-association information storing means, and said code words output from said variable-length encoding means in an alternating manner.
2. The variable-length code word transmission system claimed in
fast storing means for storing a previously generated code table; first re-associating means for receiving externally applied symbols during a predetermined time period, generating a re-associated code table and re-association information indicative of a relation between a symbol and a corresponding code word from said previously generated code table stored in said first storing means, based on the frequency of occurrence of the externally applied symbols during a predetermined time period; delay means for delaying and outputting the same symbols as those input to said first re-associating means during the predetermined time period; re-association information storing means for storing said re-associated code table and re-association information for each distinct received symbol and sequentially outputting said re-association information; variable-length coding means for receiving said symbols output from said delay means and generating and sequentially outputting code words according to said re-associated code table stored in said re-association information storing means; and means for multiplexing and outputting said re-association information from said re-association information storing means and said code words output from said variable-length coding means.
3. The variable-length code word transmission system claimed in
storing means for storing the same code table as that previously generated and stored in the encoder means; demultiplexing means for receiving data output from the encoder means, and dividing and outputting symbol/code-word re-association information and code words from the received data; re-associating means for receiving said re-association information from said demultiplexing means, re-associating a code-word and a corresponding symbol, and storing said re-associated code table; and variable-length decoding means for decoding said code words based on said code table stored in said re-associating means to thereby generate a symbol.
4. The variable-length code word transmission system as claimed in
5. The variable-length code word transmission system as claimed in
6. The variable-length code word transmission system claimed in
8. The variable-length encoder using a symbol/code-word re-association of a code table as claimed in
9. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
a plurality of symbol counters for counting the number of each symbol applied during the predetermined time period and storing the counted values for each of the respective symbols, said first re-associating means generating the re-associated code table and re-association information from a previously generated code table, based on the counted values.
10. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
11. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
12. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
13. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
14. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
15. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
16. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
17. The variable-length encoder using symbol/code-word re-association of a code table as claimed in
19. The variable-length decoder as claimed in
20. The variable-length decoder for decoding the output from a variable-length encoder using symbol/code-word re-association of a code table as claimed in
21. The variable-length decoder for decoding the output from a variable-length encoder using symbol/code-word re-association of a code table as claimed in
22. The variable-length decoder for decoding the output from a variable-length encoder using symbol/code-word re-association of a code table as claimed in
24. The variable-length decoder for decoding output from a variable-length encoder using symbol/code-word re-association of a code table as claimed in
25. The variable-length decoder for decoding output from a variable-length encoder using symbol/code-word re-association of a code table as claimed in
27. A variable-length encoding method as claimed in
28. A variable-length encoding method as claimed in
29. A variable-length encoding method as claimed in
31. A variable-length decoding method as claimed in
32. A variable-length decoding method as claimed in
33. A variable-length decoding method as claimed in
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35. A variable-length decoding method as claimed in
0. 38. The variable-length encoding method as claimed in
0. 39. The variable-length encoding method as claimed in
0. 40. The variable-length encoding method as claimed in
0. 41. The variable-length encoding method as claimed in
0. 42. The variable-length encoding method as claimed in
0. 44. The variable-length decoding method as claimed in
0. 45. The variable-length decoding method as claimed in
0. 46. The variable-length decoding method as claimed in
0. 47. The variable-length decoding method as claimed in
0. 48. The variable-length decoding method as claimed in
0. 50. The variable-length decoding method as claimed in
0. 51. The variable-length decoding method as claimed in
0. 52. The variable-length decoding method as claimed in
0. 53. The variable-length decoding method as claimed in
0. 54. The variable-length decoding method as claimed in
0. 56. The variable-length encoding method as claimed in
0. 57. The variable-length encoding method as claimed in
0. 58. The variable-length encoding method as claimed in
0. 59. The variable-length encoding method as claimed in
0. 60. The variable-length encoding method as claimed in
0. 62. The variable-length decoding method as claimed in
0. 63. The variable-length decoding method as claimed in
0. 64. The variable-length decoding method as claimed in
0. 65. The variable-length decoding method as claimed in
0. 66. The variable-length decoding method as claimed in
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This is a continuation of application Ser. No. 08/381,649 filed Jan. 31, 1995 now abandoned.
1. Field of the Invention
The present invention relates to a variable-length encoding/decoding system for video data. More particularly, it relates to a variable-length encoding/decoding system which re-associates a predetermined relation between a symbol and a code-word based on the frequency of occurrence of symbols to be variable-length coded (VLC), to thereby increase encoding efficiency.
2. Description of the Prior Art Recently, video and audio equipment employing digital signal processing methods have increased, and have been briskly developed. Therefore, many studies have been initiated relating to encoding a video and audio signal into a digital signal. Since an encoded video signal requires a large amount of digital data, various methods have been suggested to compress the encoded digital data prior to storing it on a recording medium. Among the various compression methods are a transform coding method, vector-quantization method, differential pulse coded modulation (DPCM), and variable-length coding method. Such coding methods are used to remove redundant data contained in a digital signal and, thus, reduce the total amount of transmitted or recorded data.
The VLC method is a technique to convert symbols in the form of [run,level], obtained through discrete cosine transform (DCT), quantization and zigzag scan operations, into corresponding code words by using a VLC table.
However, if there is difference between the frequency of occurrence of symbols used in constructing VLC table 2 and the corresponding VLD table 4, and that of symbols currently used in VLC coding, optimum variable-length coding can not be achieved. In other words, if the characteristics of an image to be currently variable-length coded are different from those of an image used when a code table is designed, a previously generated VLC table 2 and VLD table 4 cannot be changed to accommodate the differing characteristics. Thus, such an encoder/decoder and method do not fully accomplish the object of compressing the entire amount of data to be stored or transmitted.
Therefore, it is an object of the present invention to provide a variable-length encoder in which, even though the symbol/code-word association of a previously generated code table is used, the frequency of occurrence of the currently input symbols is measured in order to re-associate the symbols to the appropriate code words. Such a re-association provides that the amount of data to be consumed is minimized even when symbols are input that have a different frequency of occurrence from that of symbols considered when the code table is generated.
Another object of the present invention is to provide a variable-length decoder for restoring the original symbols represented by the code words obtained by variable-length coding, in which a symbol corresponding to an input code word is searched for in a previously generated decode table according to symbol/code-word re-association control information, to thereby decode the corresponding symbol.
To accomplish the first object of the present invention, there is provided a variable-length encoder using symbol/code-word re-association of a code table comprising a first storing means for storing previously generated code table, a first re-associating means for generating re-associated code table and re-association information indicative of the relation between a symbol and a corresponding code word from the previously generated code table stored in the first storing means, based on the frequency of occurrence of externally applied symbols during a predetermined time period, a delay for delaying and outputting the same symbols as those input to the first re-associating means during the predetermined time period, a re-association information storing means for storing the re-associated code table and re-association information and sequentially outputting the re-association information, variable-length coding means for receiving the delayed symbols and generating the sequentially outputting code words according to the re-associated code table stored in the re-association information storing means, and means for multiplexing and outputting the re-association information from the re-association information storing means and outputting the code words output from the variable-length coding means.
To accomplish the second object of the present invention, there is provided a variable length decoder using symbol/code-word re-association of a code table comprising a second storing means for storing the same code table as that previously generated and stored in the first storing means, demultiplexing means for receiving data output from the means for multiplexing, dividing and outputting re-association information and code words, a second re-association means for receiving the re-association information from the demultiplexing means, re-associating a corresponding symbol/code-word relation, and storing re-associated code table, and variable-length decoding means for decoding an input code word based on the code table information stored in the second re-associating means to thereby generate a symbol.
The above objects and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which:
Referring to
First re-associating circuit 13 receives the same symbol as that input to delay circuit 10, in order to re-associate the relation of symbol/code-word in a code table. In particular, first re-associating circuit 13 performs a code table re-association operation by using the symbols which are input during the predetermined time period. The predetermined time period is that time period required to gather an appropriate number of symbols for re-associating the symbols and code words in the code table. In typical applications the predetermined time period is set to correspond to one video frame or one slice. First re-associating circuit 13 reads out a code table from a first storing portion 14 and stores the read-out information in a built-in memory (not shown). First re-associating circuit 13 performs the code table re-association operation by using the code table stored in the memory and the symbols input during the predetermined time period. The code table re-association operation is explained in detail below with reference to FIG. 5.
The left-hand column shown in
Prior to re-association of a code table, the symbol counters of
The present invention can be modified in the following manner, which, however, is not applied to the embodiment described above, rather than transmitting only one symbol/code-word re-association information I(n) with respect to multiple instances of a same symbol previously generated, corresponding symbol/code-word re-association information is multiplexed and transmitted whenever a code word corresponding to a symbol that is the same as a previously generated symbol is transmitted.
Referring to
Accordingly, in the present invention, even when the frequency of occurrence of symbols during a predetermined time period is different from that of symbols earlier used in constructing a code tale, the code length of the code words generated by variable-length coding can be reduced. This decreases the amount of data transmitted or stored over that stored or transmitted when the previously generated pre-defined code table is used. Further, the present invention can efficiently transmit information for symbol/code-word re-association to a decoder, thus, increasing the compression efficiency of data transmitted to decoders.
While the present invention has been shown and described with reference to particular embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the following claims.
Park, Ju-ha, Jeong, Jechang, Jeon, Byeung-woo
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