EP-3977733-B1 - COEFFICIENT CODING FOR TRANSFORM SKIP MODE IN VIDEO CODING

EP3977733B1EP 3977733 B1EP3977733 B1EP 3977733B1EP-3977733-B1

Inventors

KARCZEWICZ, MARTA
WANG, HONGTAO
COBAN, MUHAMMED ZEYD
Chao, Yung-Hsuan

Dates

Publication Date: 20260506
Application Date: 20200529

Claims (13)

A method of coding video data, the method comprising: determining that a current block of the video data is coded in transform-skip mode, coding (400), in an interleaving manner, coefficient information on a coefficient-by-coefficient basis for coefficients in a residual block of the current block in a first pass based on the current block being coded in the transform-skip mode, wherein the coefficient information for a coefficient includes one or more of: a significance flag indicating whether a value of the coefficient is not zero, a parity flag indicating whether the value of the coefficient is odd or even, a sign flag indicating whether the value of the coefficient is positive or negative, and one or more greater than flags indicating whether an absolute value of the coefficient is greater than respective threshold values; and wherein coding, in the interleaving manner, the coefficient information comprises: context-based coding, in the interleaving manner, coefficient information on the coefficient-by-coefficient basis as regular coded bins until a coded bin count limit is reached, wherein the coded bin count limit is an upper limit for the number of regular coded bins that is used in the current block being coded in transform-skip mode; and bypass coding, in the interleaving manner, coefficient information on the coefficient-by-coefficient basis after the coded bin count limit is reached; after the first pass, coding (402) remainder information for coefficients in the residual block of the current block in a second pass based on the current block being coded in the transform-skip mode, wherein coding the remainder information comprises: coding information indicative of a remaining absolute value of a particular coefficient, wherein the coded bin count limit is reached during the coding of the particular coefficient; and coding respective values of coefficients following the particular coefficient.
The method of claim 1, wherein, in the transform skip mode, a transformation of the coefficients in the residual block from one domain to another domain is skipped.
The method of claim 1, wherein coding the remainder information comprises bypass coding the remainder information.
The method of claim 1, wherein coding comprises decoding, and wherein coding, in the interleaving manner, comprises parsing, in the interleaving manner, the coefficient information on the coefficient-by-coefficient basis for coefficients in the residual block of the current block in the first pass, and wherein coding the remainder information comprises parsing the remainder information for coefficients in the residual block of the current block in the second pass.
The method of claim 1, wherein coding comprises encoding, and wherein coding, in the interleaving manner, comprises signaling, in the interleaving manner, the coefficient information on the coefficient-by-coefficient basis for coefficients in the residual block of the current block in the first pass, and wherein coding the remainder information comprises signaling the remainder information for coefficients in the residual block of the current block in the second pass.
A device for coding video data, the device comprising: a memory (106; 120) configured to store video data; and processing circuitry (200; 300) configured to: determine that a current block of the video data is coded in transform-skip mode, code, in an interleaving manner, coefficient information on a coefficient-by-coefficient basis for coefficients in a residual block of the current block in a first pass based on the current block being coded in the transform-skip mode, wherein the coefficient information for a coefficient includes one or more of: a significance flag indicating whether a value of the coefficient is not zero, a parity flag indicating whether the value of the coefficient is odd or even, a sign flag indicating whether the value of the coefficient is positive or negative, and one or more greater than flags indicating whether an absolute value of the coefficient is greater than respective threshold values; and wherein to code, in the interleaving manner, the coefficient information, the processing circuitry is configured to: context-based code, in the interleaving manner, coefficient information on the coefficient-by-coefficient basis as regular coded bins until a coded bin count limit is reached, wherein the coded bin count limit is an upper limit for the number of regular coded bins that is used in the current block being coded in transform-skip mode; and bypass code, in the interleaving manner, coefficient information on the coefficient-by-coefficient basis after the coded bin count limit is reached. after the first pass, code remainder information for coefficients in the residual block of the current block in a second pass based on the current block being coded in the transform-skip mode, wherein to code the remainder information, the processing circuitry is configured to: code information indicative of a remaining absolute value of a particular coefficient, wherein the coded bin count limit is reached during the coding of the particular coefficient; and code respective values of coefficients following the particular coefficient.
The device of claim 6, wherein the processing circuitry, in the transform skip mode, is configured to skip a transformation of the coefficients in the residual block from one domain to another domain.
The device of claim 6, wherein to code the remainder information, the processing circuitry is configured to bypass code the remainder information.
The device of claim 6, wherein the processing circuitry comprises a video decoder, wherein to code, in the interleaving manner, the processing circuitry is configured to parse, in the interleaving manner, the coefficient information on the coefficient-by-coefficient basis for coefficients in the residual block of the current block in the first pass, and wherein to code the remainder information, the processing circuitry is configured to parse the remainder information for coefficients in the residual block of the current block in the second pass.
The device of claim 6, wherein the processing circuitry comprises a video encoder, wherein to code, in the interleaving manner, the processing circuitry is configured to signal, in the interleaving manner, the coefficient information on the coefficient-by-coefficient basis for coefficients in the residual block of the current block in the first pass, and wherein to code the remainder information, the processing circuitry is configured to signal the remainder information for coefficients in the residual block of the current block in the second pass.
The device of claim 6, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.
A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to: determining that a current block of video data is coded in transform-skip mode, code, in an interleaving manner, coefficient information on a coefficient-by-coefficient basis for coefficients in a residual block of the current block in a first pass based on the current block being coded in the transform-skip mode, wherein the coefficient information for a coefficient includes one or more of: a significance flag indicating whether a value of the coefficient is not zero, a parity flag indicating whether the value of the coefficient is odd or even, a sign flag indicating whether the value of the coefficient is positive or negative, and one or more greater than flags indicating whether an absolute value of the coefficient is greater than respective threshold values; and wherein the instructions that cause the one or more processors to code, in the interleaving manner, the coefficient information comprise instructions that cause the one or more processors to: context-based code, in the interleaving manner, coefficient information on the coefficient-by-coefficient basis as regular coded bins until a coded bin count limit is reached wherein the coded bin count limit is an upper limit for the number of regular coded bins that is used in the current block being coded in transform-skip mode; and bypass code, in the interleaving manner, coefficient information on the coefficient-by-coefficient basis after the coded bin count limit is reached; after the first pass, code remainder information for coefficients in the residual block of the current block in a second pass based on the current block being coded in the transform-skip mode; wherein the instructions that cause the one or more processors to code the remainder information comprise instructions that cause the one or more processors to: code information indicative of a remaining absolute value of a particular coefficient, wherein the coded bin count limit is reached during the coding of the particular coefficient; and code respective values of coefficients following the particular coefficient.
The computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to carry out the method of any one of claims 2- 5.

Description

TECHNICAL FIELD This disclosure relates to video encoding and video decoding. BACKGROUND Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones, so-called "smart phones," video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, Advanced Video Coding (AVC), ITU-T H.265/High Efficiency Video Coding (HEVC), and extensions of such standards. The video devices may transmit, receive, encode, decode, and/or store digital video information more efficiently by implementing such video coding techniques. Video coding techniques include spatial (intra-picture) prediction and/or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs) and/or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction with respect to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. JVET-M0464-v1 discloses with regard to "Reduction of context coded bins": The first scanning pass, i.e., the transmission of the sig_coeff_flag, abs_level_gtl_flag, and par_level_flag syntax elements, is unchanged. However, the limit on the maximum number of context coded bins per sample (CCBs) is removed and handled differently. The reduction of CCBs can be guaranteed by specifying a mode with CCB > k as invalid with k being a positive integer number. Note that k=2 for the regular level coding mode of the current VVC development. Such a limitation corresponds to a reduction of the quantization space. JVET-N0455-v3 discloses that syntax elements sig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, par_level _flag, that are coded interleaved residual sample by residual sample in the first pass followed by abs_level_gtX_flag bitplanes are converted to bitplane coding in sig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, abs_level_gtX_flag (X: 3,5,..) followed by par_level_flag bitplane order. Context modelling of syntax elements as well as abs_remainder coding is same as in CE8-4.4a. JVET-N1027-v1 proposed to use a transform block (TB) level constraint for maximum number of context-coded bins instead of coefficient subblock-level constraint. Two tests are evaluated. JCTVC-H0510 discloses a High Throughput Binarization (HTB) coding structure is the same as those of CABAC in last position coding and significance map coding. For the level coding, two binarization modes such as HTB mode (HTB== 1) and conventional coding mode (HTB=0) are selectively employed based on the number of significant coefficients. JCTVC-H0554 propose to encode grlFlag and gr2Flag only for a few starting non-zero coefficients in inverse scan order. Two schemes offer different trade-offs of throughput and compression efficiency. Scheme I a. Encode gr1Flag until two coefficients with absolute level greater than 1 are encountered in a subset. b. Encode gr2Flag only for the first coefficient with absolute level greater than 1 in a subset. Scheme II a. Encode gr 1 Flag only for the first N non-zero coefficients in a subset. b. Encode gr2Flag only for the first coefficient with absolute level greater than 1 in a subset. SUMMARY The invention is defined by the appended independent claims. Advantageous embodiments are subject to the dependent claims. In the following, each of the described methods, apparatuses, systems, examples and aspects, which does not fully correspond to the invention as defined in the appended claims, is thus not according to the invention and is, as well as the whole following description, present for illustration purposes only or to highlight specific aspects or features of the appended claims. In general, this disclosure describes techniques for coefficient coding such as in examples of transform skip mode. In transform skip mode, rather than performing transformation of residual data from one domain to another (e.g., sample domain to transformed domain), the transformation is skipped. The