Transform skip residual coding
Several techniques for video encoding and video decoding are described. One example method includes performing a conversion between a block of a video and a bitstream of the video according to a rule. The rule specifies that whether a syntax flag indicating whether transform skip residual coding is enabled at a video unit level is present in the bitstream is based on values of a first syntax element indicating usage of sign data hiding in the video unit and a second syntax element indicating usage of dependent quantization in the video unit.
1 . A method for processing video data, comprising:
performing a conversion between a video comprising one or more video units and a bitstream of the video according to a rule,
wherein the rule specifies that a syntax flag related to transform skip residual coding is conditionally included in the bitstream at a video unit level based on values of a first syntax element indicating usage of sign data hiding at the video unit level and a second syntax element indicating usage of dependent quantization at the video unit level, and
wherein the second syntax element is conditionally included in the bitstream based on a fourth syntax element in a sequence parameter set indicating whether the dependent quantization is enabled at a sequence level.
2 . The method of claim 1 , wherein a video unit from the one or more video units is a slice, and the video unit level corresponds to a slice level, and
wherein the syntax flag is represented as ts_residual_coding_disabled_flag in a slice header.
3 . The method of claim 1 , wherein whether the syntax flag is included in the bitstream is further based on a third syntax element in a sequence parameter set indicating whether transform skip is allowed at a sequence level, and
wherein the syntax flag is present in case a value of the third syntax element specifies that the transform skip is allowed at the sequence level, a value of the second syntax element specifies that the dependent quantization is not used for a video unit from the one or more video units, and a value of the first syntax element specifies that the sign data hiding is not used for the video unit.
4 . The method of claim 3 , wherein the third syntax element is represented as sps_transform_skip_enabled_flag in the sequence parameter set,
wherein the value of the third syntax element specifying that the transform skip is allowed at the sequence level is equal to 1, the value of the second syntax element specifying that the dependent quantization is not used for a video unit from the one or more video units is equal to 0, and the value of the first syntax element specifying that the sign data hiding is not used for the video unit is equal to 0,
wherein the first syntax element indicating the usage of the sign data hiding in the video unit has a default value of 0 in case the first syntax element is not present, and
wherein the second syntax element indicating the usage of the dependent quantization in the video unit has a default value of 0 in case the second syntax element is not present.
5 . The method of claim 1 , wherein the first syntax element is conditionally included in the bitstream based on the fourth syntax element in the sequence parameter set indicating whether the sign data hiding is enabled at the sequence level and the second syntax element.
6 . The method of claim 1 , wherein, in case transform skip is enabled, the sign data hiding and the dependent quantization are not applicable for a video unit from the one or more video units.
7 . The method of claim 1 , wherein the transform skip residual coding is a transform coefficient coding technique applied for a video block which is coded with transform skip mode,
wherein the sign data hiding is a technique that omits coding of a coefficient sign flag, or
wherein the dependent quantization is a mode in which quantization of a sample depends on state of previous samples.
8 . The method of claim 1 , wherein the video comprises a video picture, and
wherein the rule further specifies that at least one of scaling window offsets applicable to the video picture is no less than X, where X is a negative integer value determined based on a dimension of the video picture,
wherein the scaling window offsets comprises at least one of a scaling window right offset, a scaling window left offset, a scaling window top offset, or a scaling window bottom offset, and
wherein the dimension of the video picture comprises a picture width represented in luma samples or a picture height represented in luma samples.
9 . The method of claim 8 , wherein a value of SubWidthC*(scaling_win_left_offset+scaling_win_right_offset) is less than the picture width represented in luma samples, and a value of SubHeightC*(scaling_win_top_offset+scaling_win_bottom_offset) is less than the picture height represented in luma samples, where scaling_win_left_offset denotes the scaling window left offset, scaling_win_right_offset denotes the scaling window right offset, scaling_win_top_offset denotes the scaling window top offset, scaling_win_bottom_offset denotes the scaling window bottom offset, and SubWidthC and SubHeightC are determined based on a chroma format of the video picture.
10 . The method of claim 1 , wherein the rule specifies that a type of an adaptation parameter set is indicated prior to an identifier of the adaptation parameter set.
11 . The method of claim 1 , wherein the conversion includes encoding the video into the bitstream.
12 . The method of claim 1 , wherein the conversion includes decoding the video from the bitstream.
13 . An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
perform a conversion between a video comprising one or more video units and a bitstream of the video according to a rule,
wherein the rule specifies that a syntax flag related to transform skip residual coding is conditionally included in the bitstream at a video unit level based on values of a first syntax element indicating usage of sign data hiding at the video unit level and a second syntax element indicating usage of dependent quantization at the video unit level, and
wherein the second syntax element is conditionally included in the bitstream based on a fourth syntax element in a sequence parameter set indicating whether the dependent quantization is enabled at a sequence level.
14 . The apparatus of claim 13 , wherein a video unit from the one or more video units is a slice, and the video unit level corresponds to a slice level, and wherein the syntax flag is represented as ts_residual_coding_disabled_flag in a slice header.
15 . The apparatus of claim 13 , wherein whether the syntax flag is included in the bitstream further based on a third syntax element in a sequence parameter set indicating whether transform skip is allowed at a sequence level,
wherein the syntax flag is present in case a value of the third syntax element specifies that transform skip is allowed at the sequence level, a value of the second syntax element specifies that the dependent quantization is not used for a video unit from the one or more video units, and a value of the first syntax element specifies that the sign data hiding is not used for the video unit,
wherein the third syntax element is represented as sps_transform_skip_enabled_flag in the sequence parameter set,
wherein the value of the third syntax element specifying that transform skip is allowed at the sequence level is equal to 1, the value of the second syntax element specifying that the dependent quantization is not used for the video unit is equal to 0, and the value of the first syntax element specifying that the sign data hiding is not used for the video unit is equal to 0,
wherein the first syntax element indicating the usage of the sign data hiding in the video unit has a default value of 0 in case the first syntax element is not present, and
wherein the second syntax element indicating the usage of the dependent quantization in the video unit has a default value of 0 in case the second syntax element is not present.
16 . The apparatus of claim 13 ,
wherein the first syntax element is conditionally included in the bitstream based on the fourth syntax element in the sequence parameter set indicating whether the sign data hiding is enabled at the sequence level and the second syntax element.
17 . The apparatus of claim 13 , wherein, in case transform skip is enabled, the sign data hiding and the dependent quantization is not applicable for a video unit from the one or more video units,
wherein the transform skip residual coding is a transform coefficient coding technique applied for a video block which is coded with transform skip mode,
wherein the sign data hiding is a technique that omits coding of a coefficient sign flag, or
wherein the dependent quantization is a mode in which quantization of a sample depends on state of previous samples, and
wherein the video comprises a video picture.
18 . A non-transitory computer-readable storage medium storing instructions that cause a processor to:
perform a conversion between a video comprising one or more video units and a bitstream of the video according to a rule,
wherein the rule specifies that a syntax flag related to transform skip residual coding is conditionally included in the bitstream at a video unit level based on values of a first syntax element indicating usage of sign data hiding at the video unit level and a second syntax element indicating usage of dependent quantization at the video unit level, and
wherein the second syntax element is conditionally included in the bitstream based on a fourth syntax element in a sequence parameter set indicating whether the dependent quantization is enabled at a sequence level.
19 . A method for storing a bitstream of a video, comprising:
generating the bitstream of the video comprising one or more video units according to a rule; and
storing the bitstream in a non-transitory computer-readable recording medium,
wherein the rule specifies that a syntax flag related to transform skip residual coding is conditionally included in the bitstream at a video unit level based on values of a first syntax element indicating usage of sign data hiding at the video unit level and a second syntax element indicating usage of dependent quantization at the video unit level, and
wherein the second syntax element is conditionally included in the bitstream based on a fourth syntax element in a sequence parameter set indicating whether the dependent quantization is enabled at a sequence level.