WO2006034647A1 - Procede de decodage et de codage a longueur variable - Google Patents

Procede de decodage et de codage a longueur variable Download PDF

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Publication number
WO2006034647A1
WO2006034647A1 PCT/CN2005/001587 CN2005001587W WO2006034647A1 WO 2006034647 A1 WO2006034647 A1 WO 2006034647A1 CN 2005001587 W CN2005001587 W CN 2005001587W WO 2006034647 A1 WO2006034647 A1 WO 2006034647A1
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Prior art keywords
variable length
class
length code
code
bit
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PCT/CN2005/001587
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English (en)
Chinese (zh)
Inventor
Zhong Luo
Jing Wang
Linhua Ma
Yilin Chang
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Huawei Technologies Co., Ltd.
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Publication of WO2006034647A1 publication Critical patent/WO2006034647A1/fr

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M7/00—Conversion of a code where information is represented by a given sequence or number of digits to a code where the same, similar or subset of information is represented by a different sequence or number of digits
    • H03M7/30—Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
    • H03M7/40—Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/136—Incoming video signal characteristics or properties
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
    • H04N19/91—Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Definitions

  • the present invention relates to video codec techniques, and more particularly to a variable length codec method.
  • variable length code In source entropy compression, compressing data using variable length code (VLC) is one of the most commonly used methods.
  • Huffinan variable length coding for a given source and source symbol [Huffman DA, "A method for construction of minimum redundancy codes", Proc. IRE, Vol 40, pp. 1098-1101, Sep. 1952. ] You can get the shortest average code length and effectively compress the source.
  • the Huffman code is very sensitive to the error code. Usually, a bit error will cause the subsequent variable length codes to be decoded correctly, that is, the start and end positions of the variable length code cannot be correctly located, so the variable length code is used when there is noise interference. error diffusion is very serious, when the bit error rate 10--4, the variable length code symbol error rate as high as 10-2 or more.
  • variable length code symbol refers to a binary bit string representing a "source symbol", for example, in Table 1, for a Huffinan code, the variable length code symbol representing the source symbol S1 is "00"; representing a source symbol The variable length code symbol of S2 is "01".
  • the variable length code symbol error refers to any bit error in the variable length code symbol, and the symbol is an error, thereby counting the variable length code symbol error probability, not the statistical bit error probability.
  • Insertion error that is, a variable length code is decoded into two or more variable length code symbols.
  • the symbol of the variable length code is incorrect. It means that only the symbol substitution error occurs in the variable length code, and the variable length
  • the sequence number of the code (that is, the sequence number of any variable length code in the data stream) has not changed, and is hereinafter referred to as the first type of error.
  • variable length code The serial number of the variable length code is incorrect. It is caused by the insertion and deletion of the variable length code. That is, because one or more variable length codes are inserted or deleted, the subsequent variable length code number will be corresponding.
  • the ground is increased or decreased, which is hereinafter referred to as the second type of error.
  • variable length codes When an error occurs, some variable length codes will have both the first type and the second type of error; some variable length codes are decoded correctly, there is no first type of error, but because of the insertion and deletion errors in front of them, the serial number It will increase or decrease accordingly, that is, a second type of error will occur accordingly.
  • variable length code schemes proposed for the error diffusion effect of Huffman variable length codes are only the first type of errors that reduce variable length codes, such as fast sync comma code and reverse solvable long code (Reversible).
  • VLC hereinafter referred to as RVLC
  • RVLC right side chain code
  • Table 5 lists the Huffman code, comma code, and RVLC's 5 source symbol encoding examples.
  • the Huffman code has the shortest average code length, but it is prone to error spread, resulting in the first and second types of errors of the variable length code.
  • a bit error will cause many subsequent source symbols to be decoded incorrectly, and insert and delete errors will occur; the question mark in the figure indicates that the corresponding code table is exceeded and cannot be decoded correctly.
  • RVLC is characterized by being able to decode from both the forward and reverse directions. When a variable length code decoding error is found, it can be decoded from the reverse direction to recover the variable length code as much as possible. Although RVLC can decode in the reverse direction, in the decoding of the two directions, it is difficult to determine the error from the codeword itself. Where is it, as shown in Figure 3, it is difficult to determine which of the forward and reverse decoding errors in the question mark is a true error, so it is difficult to determine which codewords are truly correctly decoded codewords. In practical applications, the rationality of the codewords solved can usually be judged by the actual content of the codec.
  • comma code has the function of fast synchronization. Only one of them is shown in Table 1. There are other types of comma codes, but the functions are similar. Although comma code overcomes the error diffusion effect of Huffman code, it often has insertion and deletion errors, and it is easy to produce the second type of error of variable length code. As shown in Figure 2, one bit in the source S5 is incorrect, so that S5 is decoded into S2 and S3, which is equivalent to an insertion error. At this time, although the right side of S1, S2, and S3 continue to decode normally, Their serial numbers will be incremented by 1, which is the second type of error.
  • variable length codes with synchronization function can effectively reduce the first type of error, that is, the symbol substitution error of the variable length code; however, if an insertion and deletion error occurs, all subsequent changes are made.
  • the long code will have a serial number error, which is the second type of error, which is a major factor affecting the correctness of video decoding.
  • the present invention provides a new variable length code encoding and decoding method to solve the problem that the second type of error is easy to occur in the existing variable length code encoding and decoding method, thereby eliminating the variable length code.
  • the serial number of the variable length code caused by the insertion and deletion error is incorrect.
  • the technical solution of the present invention is to provide a variable length code encoding and decoding method, which is used for encoding and decoding a source, and the method includes the following steps:
  • the coded stream is subjected to a variable length code alternate code according to the rules at the time of encoding.
  • L is a natural number greater than or equal to 2, and is identified as LI, L2 LL, and the source may be LI, L2 in any of the following alternate manners.
  • variable length code after each L1 type variable length code is L2 type variable length code
  • variable length code after each L2 type variable length code is L3 type variable length code
  • LL class Variable length code the variable length code after each LL class variable length code is an L1 type variable length code
  • variable length code after every two L1 class variable length codes is two L2 class variable length codes, each two The variable length code behind the L2 class variable length Ma is two L3 class variable length codes, and so on, until the LL class variable length code, the variable length code after each two LL class variable length codes is two L1 type variable length code;
  • Each Ml L1 class variable length code is followed by M2 L2 class variable length codes, 3 M3 L3 class variable length codes after every M2 L2 class variable length codes, and so on, until ML LLs
  • the source can be alternately coded according to any of the following alternate modes:
  • variable length code after each class A variable length code can only be a class B variable length code, and the variable length code after each class B variable length code can only be a class A variable length code;
  • Each M class A variable length code is followed by N class B variable length codes, and each N class B variable length code is followed by M [A class A variable length code, where M and N are natural numbers.
  • the class A variable length code "0" is used as the synchronization bit, "1" is used as the cutoff bit, and at least one information bit X is between any two adjacent sync bits. There is at least one information bit X between the cut-off bit and the previous sync bit, and the value of the information bit X can be "0" or " ⁇ ; in the B-type variable length code, "1" is used as The sync bit, with "01" as the cutoff bit, has at least one information bit X before the cutoff bit and before any sync bit, and at least one information bit X between the adjacent two sync bits, in front of the cutoff bit There is at least one information bit X between the synchronization bits, and the value of the information bit X can be "0" or "1".
  • the definition forms of the A and B variable length codes can also be interchanged.
  • the probability of the source symbol is further counted, and the source symbol with the highest probability of occurrence is represented by the shortest code;
  • the source symbol with the second highest rate is represented by the same or the shortest length of the code.
  • the probability of occurrence the source symbol is small, it is represented by the longest code.
  • step (2) of the method described in the third of the present invention when the source is decoded, if the synchronization bit of a variable length code is in error, the maximum error of the variable length code is determined, and the one with the highest probability is used. The hometown of the error correction scheme is used as the decoding output.
  • the posterior probability when decoding the source, if the synchronization bit of a variable length code is in error, the posterior probability can be used to determine the maximum error probability of the variable length code, and the posterior error is used. The result of the most probable one is the decoded output.
  • variable length code errors caused by bit errors there are two possibilities for variable length code errors caused by bit errors, one is information bit error, which does not affect the synchronization of variable length code symbols; the other case is synchronization bit error.
  • the synchronization bit error occurs, if the decoding is directly performed without correcting, it will violate the rule that the A and B variable length codes should be alternately output; at this time, the posterior probability can be used to judge the maximum error probability, and the posterior probability is the largest.
  • the output is decoded to maintain the rule that the A and B variable length codes should be alternately output, so that no insertion or deletion errors occur, and the serial number of each variable length code can remain unchanged, that is, the second type does not occur. error.
  • Figure 1 is a schematic diagram of error propagation of Huffman horses
  • FIG. 2 is a schematic diagram of error diffusion of a comma code
  • Figure 3 is a schematic diagram of error propagation of the RVLC code.
  • the syntax units of the coding such as DCT coefficients, motion vector symbols, etc.
  • the decoded variable length code not only requires the source symbol itself to be decoded correctly, but also requires that the sequence number of the source symbol be decoded correctly so that the video decoder can reconstruct the image correctly.
  • the present invention proposes a new variable length code encoding and decoding method, referred to herein as an alternate variable length code (Alternate VLC, referred to as AVLC), which alternates the source by at least two types of variable length codes.
  • This alternate variable length code can not only quickly synchronize to reduce the first type of error of the variable length code, but also effectively overcome the second type of error of the variable length code.
  • the source and the two types of variable length codes can be alternately coded in the following alternate manner:
  • variable length code after each class A variable length code can only be a class B variable length code.
  • the length code after each class B variable length code can only be a class A variable length code, that is, ABABAB. .., or BABABA...;
  • each N class B variable length code is followed by M class A variable length codes, where M and N are natural numbers, For example ABBABB..., or BAABAABAA..., etc.;
  • alternate decoding is performed in the same manner as the encoding.
  • variable length codes A, B, and C the source code can be alternately coded with the variable length codes of eight, B, and C in any of the following alternate ways:
  • each class A variable length code is a class B variable length code
  • the variable length code after each class B variable length code is a class C variable length code
  • each class C variable length code is a class A variable length code
  • Each M class A variable length code is followed by N class B variable length codes, and each N class B variable length code is followed by P class C variable length codes, after each P class C variable length code With M class A variable length code, which, ! ⁇ and P are natural numbers.
  • variable length code is alternated, and the irregular alternating of multiple types of variable length codes can also be used.
  • variable length codes A, B, and C the alternate modes that can be used are: AABCAABC, ABBCABBC, ABCCABCC, ABBCCCABBCCC, and the like.
  • the invention can be implemented by using two types, three types or any plurality of types of variable length codes, and whether the rules of variable length codes are alternated or irregularly alternated, and the difference lies only in the complex complex of decoding, and the difference in effects, and the principle does not change. .
  • the L-type variable length can be used, and L is a natural number greater than or equal to 1, and is identified as L1.
  • L2, LL, the LI, L2 LL, and L-type variable length codes can be alternately coded according to any of the following alternatives:
  • variable length code after each L1 type variable length code is L2 type variable length code
  • variable length code after each L2 type variable length code is L3 type variable length ⁇ horse, and so on, until LL
  • the variable length code after each LL class variable length code is a LL class variable length code
  • variable length code after each two L1 type variable length codes is two L2 type variable length codes, and the variable length codes after each two L2 type variable length codes are two L3 type variable length codes, Such a push, until the LL class becomes longer Code, the variable length code after every two LL class variable length codes is two L1 class variable length codes;
  • Ml L1 class variable length codes are followed by Ml L1 class variable length codes, where Ml and M2 ML are natural numbers.
  • the first method that is, the rule of using two types of variable length codes A and B is used as an example, and the type A variable length code or the B type variable length code is composed of a synchronization bit and an information bit. Its structure is shown in Table 2 and Table 3:
  • the "X" in the class A and class B variable length codes is an information bit, and even if the codewords have the same length, the information bits take different values ⁇ 1 to become different codewords. For example, for 0x1 in class A, when X is 0, it is 001, for code table number A1; when X is 1, it is 011, corresponding to code table number A2.
  • class A and class B variable length codes The difference between the class A and class B variable length codes is that "0" in the eight types of 3 ⁇ 4 long codes is the synchronization bit, "1" is the cutoff bit; "in the class B variable length code is the synchronization bit, and "01" is The cut-off bit; the serial number 0 of the B-type variable length code does not exist. From its shield, the A-type variable length code and the B-type variable length code are actually comma code, so it can effectively prevent the lengthening itself. The first type of error of the code. Of course, the definition of the A and B variable length codes can also be adjusted to each other.
  • variable length codes can be generated by an algorithm without storing a code table.
  • the algorithm is as follows:
  • N Int[log 2 (Code_number+ 1 )] + 1;
  • Codeward ® [Info] 2 Ni ; Where N is the information bit length, Int[ ] indicates that the mantissa is rounded off, Info indicates the value of the information bit, Codeward is the code word, that is, the obtained binary variable length code symbol, [Info] ⁇ indicates "Info""Information bits expressed in binary form a Class A or Class B variable length code according to the variable length code structure of Table 2 or Table 3.
  • the source symbol with the greatest probability is represented by the shortest code, and the code table is allocated by this principle; if the previous source is encoded with the class A code table, Then a source symbol should be encoded with a Class B code table, then a Class A code table, then a Class B code table, and so on.
  • a and B variable length codes alternate.
  • the encoded code stream is subjected to alternate decoding of eight types and IB variable length codes.
  • the source decoding alternately decodes the output according to the class A and class B variable length codes.
  • class A variable length codes AQ does not participate in coding, and the shortest code length is encoded from the beginning; for class B variable length codes, 8 1 and does not participate in coding, and the shortest code length is encoded from B 3 . This approach sacrifices coding efficiency in exchange for error resistance.
  • variable length code errors caused by bit errors
  • one is information bit error, which does not affect the synchronization of variable length code symbols
  • the other case is synchronization bit error, synchronization bit
  • the maximum posterior probability can be used to determine its maximum error probability and correct its error.
  • Source decoding 0x0x0x0x1 ⁇ xlxlxlxlxOl
  • Decoding error correction method one: 0x0x0x0x1 xOxOxlxlxlxlxlxOl
  • Decoding error correction method 2 0x0x0x0x1x0x0x1 xlxlxlxlxOl
  • the original transmitted codeword ..., 8 ⁇ 1, 881, ...)
  • the source decoding is (..., 8 ⁇ 2, , 881 7)
  • X is judged to be a class A code or a class B code, which violates the requirement of alternate output of A and B code words, so it can be determined that it is part of the previous class A code or the latter class B code. a part of. If X and SB1 codewords are combined and judged as SB2 codewords, then i people are consecutively having 2 sync codeword errors in the transmission process of SB2 codewords.
  • P ⁇ b Pt is about 1000 times larger (since the two decoding algorithms, only 3 bits are changing, so the above probability only considers 3 bits).
  • the SA3 and SB1 outputs should be selected, that is, the originally transmitted codewords (..., SA1, SB1, ...) become (..., SA3, SB1, ). It can be seen that the alternate coding mode of the alternate variable length code and the structure of the codeword can effectively find and correct the error, not only synchronize the variable length code symbols, but also correct the bit errors of the synchronization bits.
  • the soft information of the signal output value can be obtained from the demodulator, a more accurate posterior probability information can be obtained.
  • 'J : P(S"R) ⁇ ⁇ )

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Theoretical Computer Science (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)

Abstract

La présente invention concerne un nouveau procédé de codage et de décodage à longueur variable lequel procédé permettant de résoudre les erreurs de numéro de séquences VLC qui apparaissaient souvent dans les procédés de l'art antérieur. Dans cette invention, au moins deux types de séquences VLC sont utilisés alternativement pour le codage à longueur variable lors du codage de la source des signaux, et les trains de bits sont décodés par différentes séquences VLC alternativement d'après les règles de codage lors du décodage de la source des signaux. Lorsque le bit synchronisé de l'une des séquences VLC est faux, si le décodage est directement exécuté sans correction d'erreurs, la règle des séquences VLC alternatives est détruite. A ce moment là, une probabilité à posteriori peut être utilisée pour évaluer la probabilité d'erreur maximum, et la probabilité à posteriori maximum peut être obtenue en tant que résultat du décodage, ce qui permet de conserver les séquences VLC alternatives. Selon le procédé décrit dans cette invention, il n'y a pas d'erreurs d'insertion ou de suppression, et chaque numéro d'ordre reste inchangé.
PCT/CN2005/001587 2004-09-29 2005-09-28 Procede de decodage et de codage a longueur variable WO2006034647A1 (fr)

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CN101719814B (zh) 2009-12-08 2013-03-27 华为终端有限公司 确定带内信令译码模式的方法及装置
CN102231832B (zh) * 2011-06-24 2013-04-24 北京瀚景锦河科技有限公司 变长码编解码方法和系统
CN109670353B (zh) * 2017-10-13 2021-10-22 重庆微标科技股份有限公司 一种电子设备及射频标签的解码纠错方法

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JP2002374174A (ja) * 2001-06-12 2002-12-26 Lsi Systems:Kk 可変長コード復号装置、可変長コード復号方法およびその方法をコンピュータに実行させるプログラム
JP2003230095A (ja) * 2001-11-28 2003-08-15 Victor Co Of Japan Ltd 可変長データ符号化方法及び可変長データ符号化装置
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US5801841A (en) * 1994-10-18 1998-09-01 Fuji Xerox Co., Ltd. Image signal coding apparatus with switching between variable-length coding and fixed-length coding
US5686916A (en) * 1995-12-28 1997-11-11 Philips Electronics North America Corp. Multi-code-book variable length decoder
JP2002374174A (ja) * 2001-06-12 2002-12-26 Lsi Systems:Kk 可変長コード復号装置、可変長コード復号方法およびその方法をコンピュータに実行させるプログラム
US6696992B1 (en) * 2001-10-02 2004-02-24 Allan Chu Efficient data encoding and decoding processes
JP2003230095A (ja) * 2001-11-28 2003-08-15 Victor Co Of Japan Ltd 可変長データ符号化方法及び可変長データ符号化装置

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