Updating for counter-based intra prediction mode
A video processing method includes performing a conversion between a video including a video unit and a coded representation of the video, where, after the video unit is encoded or decoded with an intra prediction mode, one or more frequence tables and/or one or more sorted intra prediction mode (IPM) tables are selectively updated according to a rule, where the one or more frequence tables include information about frequence of the intra prediction mode used for processing the video unit in the conversion, where the frequence indicates an occurrence of the intra prediction mode used for the conversion, and where the one or more sorted IPM tables indicate the intra prediction mode used in the processing.
1. A method of processing video data, comprising:
determining, for a conversion between a current video block of a video and a bitstream of the video, that a first prediction mode is applied to derive prediction samples of the current video block,
maintaining, a frequency table recording frequencies associated with one or more intra prediction modes, and
performing the conversion based on the first prediction mode,
wherein the frequencies indicate occurrences associated with the one or more intra prediction modes applied for one or more video blocks processed before the current video block,
wherein in a case that the first prediction mode is an intra prediction mode of the one or more intra prediction modes, the frequency table is updated based on a first intra prediction mode, and
wherein in response to the first prediction mode being not one intra prediction mode among the one or more intra prediction modes, the frequency table is disallowed from being updated.
2. The method of claim 1 , wherein in a case that the first prediction mode is a matrix-based intra prediction (MIP) mode, an intra block copy (IBC) mode, or a palette mode, the frequency table is disallowed from being updated.
3. The method of claim 1 , wherein in the case that the first prediction mode is the intra prediction mode of the one or more intra prediction modes, a frequency associated with the first prediction mode in the frequency table is updated by adding an integer K.
4. The method of claim 3 , wherein K is set to 1.
5. The method of claim 3 , wherein frequencies of remaining intra prediction modes of the one or more intra prediction modes are kept unchanged.
6. The method of claim 1 , wherein the one or more intra prediction modes exclude a wide-angular intra prediction mode.
7. The method of claim 1 , wherein the one or more intra prediction modes include at least one of a direct current (DC) mode, a horizontal mode, a vertical mode, or a bilinear intra prediction mode.
8. The method of claim 1 , wherein an intra prediction mode (IPM) table is further maintained for the conversion based on the frequency table, and the IPM table is initialized when an initialization process is invoked for the frequency table,
wherein the IPM table comprises N entries, N is an integer which is not smaller than two, and the N entries represents N modes with highest frequency in the frequency table, and
wherein the IPM table is updated when the frequency table is updated.
9. The method of claim 8 , wherein N is equal to 2.
10. The method of claim 8 , wherein a sorting process is applied to the IPM table according to the frequencies in the updated frequency table in response to that the first intra prediction mode satisfying
F n+l ( M l )>= F n+l ( M i )>= F n+l ( M 0 ),
where M l denotes the first intra prediction mode, M 0 and M l denotes two modes in the IPM table before being updated,
where F n+l (M) denotes the frequency associated with the mode M in the updated frequency table.
11. The method of claim 1 , wherein the current video block comprises a luma coding block.
12. The method of claim 1 , wherein indications of whether a frequency-based intra mode in which the frequency table is applied is enabled are included in a sequence parameter set and a picture header.
13. The method of claim 1 , wherein the conversion includes encoding the current video block into the bitstream.
14. The method of claim 1 , wherein the conversion includes decoding the current video block from the bitstream.
15. 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:
determine, for a conversion between a current video block of a video and a bitstream of the video, that a first prediction mode is applied to derive prediction samples of the current video block,
maintain, a frequency table recording frequencies associated with one or more intra prediction modes, and
perform the conversion based on the first prediction mode,
wherein the frequencies indicate occurrences associated with the one or more intra prediction modes applied for one or more video blocks processed before the current video block,
wherein in a case that the first prediction mode is an intra prediction mode of the one or more intra prediction modes, the frequency table is updated based on a first intra prediction mode, and
wherein in response to the first prediction mode being not one intra prediction mode among the one or more intra prediction modes, the frequency table is disallowed from being updated.
16. The apparatus of claim 15 , wherein in a case that the first prediction mode is a matrix-based intra prediction (MIP) mode, an intra block copy (IBC) mode, or a palette mode, the frequency table is disallowed from being updated.
17. The apparatus of claim 15 , wherein in the case that the first prediction mode is the intra prediction mode of the one or more intra prediction modes, a frequency associated with the first prediction mode in the frequency table is updated by adding an integer K.
18. The apparatus of claim 15 , wherein the one or more intra prediction modes include at least one of a direct current (DC) mode, a horizontal mode, a vertical mode, or a bilinear intra prediction mode.
19. A non-transitory computer-readable storage medium storing instructions that cause a processor to:
determine, for a conversion between a current video block of a video and a bitstream of the video, that a first prediction mode is applied to derive prediction samples of the current video block,
maintain, a frequency table recording frequencies associated with one or more intra prediction modes, and
perform the conversion based on the first prediction mode,
wherein the frequencies indicate occurrences associated with the one or more intra prediction modes applied for one or more video blocks processed before the current video block,
wherein in a case that the first prediction mode is an intra prediction mode of the one or more intra prediction modes, a frequency table is updated based on the first prediction mode, and
wherein in response to the first prediction mode being not one intra prediction mode among the one or more intra prediction modes, the frequency table is disallowed from being updated.
20. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises:
determining, for a current video block of a video, that a first prediction mode is applied to derive prediction samples of the current video block,
maintaining, a frequency table recording frequencies associated with one or more intra prediction modes, and
generating the bitstream based on the first prediction mode,
wherein the frequencies indicate occurrences associated with the one or more intra prediction modes applied for one or more video blocks processed before the current video block,
wherein in a case that the first prediction mode is an intra prediction mode of the one or more intra prediction modes, a frequency table is updated based on the first prediction mode, and
wherein in response to the first prediction mode being not one intra prediction mode among the one or more intra prediction modes, the frequency table is disallowed from being updated.