Low frequency non-separable transform signaling in video coding
Several techniques for video encoding and video decoding are described. A method includes performing a conversion between a video block of a video and a bitstream of the video, wherein the video block uses a low frequency non-separable transform for the conversion, wherein the bitstream conforms to a format rule that specifies that a syntax element is included at a syntax level for the bitstream, wherein the syntax element is indicative of whether use of a scaling matrix which is derived from a reference scaling list is enabled for the video block, and wherein the syntax level is a sequence level, a picture level, or a slice level.
1 . A method of video processing, comprising:
performing a conversion between a video block of a video and a bitstream of the video,
wherein the video block uses a low frequency non-separable transform for the conversion,
wherein the bitstream conforms to a format rule that specifies that a first syntax element is included at a sequence level for the bitstream,
wherein the first syntax element indicates whether use of explicit scaling matrices, for blocks coded with the low frequency non-separable transform, is enabled, and
wherein when present, the first syntax element is included in a sequence parameter set (SPS), and the first syntax element being included in the SPS is determined based on the low frequency non-separable transform being enabled,
wherein the method further comprises:
determining to apply a default scaling matrix to the video block, based on a value of the first syntax element indicating that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled and the low frequency non-separable transform being enabled for the video block.
2 . The method of claim 1 , wherein when a value of a second syntax element included in the SPS is equal to 1, the first syntax element is included in the SPS, and
wherein the value of the second syntax element equal to 1 indicates that the low frequency non-separable transform is enabled, and the second syntax element is sps_lfnst_enabled_flag.
3 . The method of claim 1 , wherein the value of the first syntax element indicating that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled is equal to 1.
4 . The method of claim 3 , wherein scaling factors of the default scaling matrix are equal to 16.
5 . The method of claim 1 , wherein the format rule further specifies that a third syntax element is included in the bitstream at a video region level to control a scaling process applied to transform coefficients or non-transform coefficients, and
wherein a video region is smaller than a video picture of the video.
6 . The method of claim 5 , wherein the format rule specifies that the video region is a slice, and the third syntax element is included in a slice header.
7 . The method of claim 1 , wherein the performing the conversion comprises encoding the video into the bitstream.
8 . The method of claim 1 , wherein the performing the conversion comprises decoding the video from the bitstream.
9 . 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 block of a video and a bitstream of the video,
wherein the video block uses a low frequency non-separable transform for the conversion,
wherein the bitstream conforms to a format rule that specifies that a first syntax element is included at a sequence level for the bitstream,
wherein the first syntax element indicates whether use of explicit scaling matrices, for blocks coded with the low frequency non-separable transform, is enabled, and
wherein when present, the first syntax element is included in a sequence parameter set (SPS), and the first syntax element being included in the SPS is determined based on the low frequency non-separable transform being enabled,
wherein the processor is further caused to:
determine to apply a default scaling matrix to the video block, based on a value of the first syntax element indicating that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled and the low frequency non-separable transform being enabled for the video block.
10 . The apparatus of claim 9 , wherein when a value of a second syntax element included in the SPS is equal to 1, the first syntax element is included in the SPS, and
wherein the value of the second syntax element equal to 1 indicates that the low frequency non-separable transform is enabled, and the second syntax element is sps_lfnst_enabled_flag.
11 . A non-transitory computer-readable storage medium storing instructions that cause a processor to:
perform a conversion between a video block of a video and a bitstream of the video,
wherein the video block uses a low frequency non-separable transform for the conversion,
wherein the bitstream conforms to a format rule that specifies that a first syntax element is included at a sequence level for the bitstream,
wherein the first syntax element indicates whether use of explicit scaling matrices, for blocks coded with the low frequency non-separable transform, is enabled, and
wherein when present, the first syntax element is included in a sequence parameter set (SPS), and the first syntax element being included in the SPS is determined based on the low frequency non-separable transform being enabled,
wherein the processor is further caused to:
determine to apply a default scaling matrix to the video block, based on a value of the first syntax element indicating that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled and the low frequency non-separable transform being enabled for the video block.
12 . The non-transitory computer-readable storage medium of claim 11 , wherein the instructions further cause the processor to:
wherein the value of the first syntax element indicating that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled is equal to 1.
13 . A method for storing a bitstream of a video, comprising:
generating the bitstream of the video from a video block of the video, and
storing the bitstream in a non-transitory computer-readable recording medium,
wherein the video block uses a low frequency non-separable transform for the generation,
wherein the bitstream conforms to a format rule that specifies that a first syntax element is included at a sequence level for the bitstream,
wherein the first syntax element indicates whether use of explicit scaling matrices, for blocks coded with the low frequency non-separable transform, is enabled, and
wherein when present, the first syntax element is included in a sequence parameter set (SPS), and the first syntax element being included in the SPS is determined based on the low frequency non-separable transform being enabled,
wherein the method further comprises:
determining to apply a default scaling matrix to the video block, based on a value of the first syntax element indicating that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled and the low frequency non-separable transform being enabled for the video block.
14 . The method of claim 13 , wherein the method further comprises:
wherein the value of the first syntax element indicating that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled is equal to 1, which indicates that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled and the low frequency non-separable transform is enabled for the video block, the default scaling matrix is applied to the video block.
15 . The apparatus of claim 9 , wherein the value of the first syntax element indicating that use of the explicit scaling matrices for blocks coded with the low frequency non-separable transform is disabled is equal to 1.
16 . The apparatus of claim 15 , wherein scaling factors of the default scaling matrix are equal to 16.
17 . The apparatus of claim 9 , wherein the format rule further specifies that a third syntax element is included in the bitstream at a video region level to control a scaling process applied to transform coefficients or non-transform coefficients, and
wherein a video region is smaller than a video picture of the video.
18 . The apparatus of claim 17 , wherein the format rule specifies that the video region is a slice, and the third syntax element is included in a slice header.
19 . The non-transitory computer-readable storage medium of claim 11 , wherein when a value of a second syntax element included in the SPS is equal to 1, the first syntax element is included in the SPS, and
wherein the value of the second syntax element equal to 1 indicates that the low frequency non-separable transform is enabled, and the second syntax element is sps_lfnst_enabled_flag.
20 . The non-transitory computer-readable storage medium of claim 11 , wherein the format rule further specifies that a third syntax element is included in the bitstream at a video region level to control a scaling process applied to transform coefficients or non-transform coefficients, and
wherein a video region is smaller than a video picture of the video.