Collocated picture indication in video bitstreams

1. A method of processing video data, comprising:

performing a conversion between a video comprising a video picture that includes a video slice and a bitstream of the video;

wherein the bitstream conforms to a format rule;

wherein the format rule specifies that a value of first certain information in a slice header for the video slice indicates a collocated picture used for a temporal motion vector prediction is derived from a reference list 0 each time a slice type of the video slice is P and a value of a first syntax element in a picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture; and

wherein the format rule further specifies whether the value of the first certain information in the slice header for the video slice is inherited from the picture header for the video picture is determined at least based on the slice type of the video slice and a value of a second syntax element indicating whether reference picture list information is present in the picture header, and wherein the second syntax element is pps_rpl_info_in_ph_flag.

2. The method of claim 1 , wherein the format rule further specifies that the value of the first certain information in the slice header for the video slice indicates that the collocated picture used for the temporal motion vector prediction is derived from the reference list 0 each time the slice type of the video slice is P, the value of the first syntax element in the picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture and the value of the second syntax element indicates that the reference picture list information is present in the picture header.

3. The method of claim 1 , wherein the format rule further specifies that a value of a third syntax element in the slice header of the video slice, which specifies a reference index of the collocated picture used for the temporal motion vector prediction, is in a range of 0 to a maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is P and the temporal motion vector prediction is enabled.

4. The method of claim 1 , wherein the format rule further specifies that a value of a third syntax element in the slice header of the video slice, which specifies a reference index of the collocated picture used for the temporal motion vector prediction, refers to an entry in the reference list 0 and is in a range of 0 to a maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is B and the value of the first certain information in the slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from the reference list 0.

5. The method of claim 1 , wherein the conversion comprises encoding the video into the bitstream.

6. The method of claim 1 , wherein the conversion comprises decoding the video from the bitstream.

7. 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 a video picture that includes a video slice and a bitstream of the video;

wherein the bitstream conforms to a format rule;

wherein the format rule specifies that a value of first certain information in a slice header for the video slice indicates a collocated picture used for a temporal motion vector prediction is derived from a reference list 0 each time a slice type of the video slice is P and a value of a first syntax element in a picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture; and

wherein the format rule further specifies whether the value of the first certain information in the slice header for the video slice is inherited from the picture header for the video picture is determined at least based on the slice type of the video slice and a value of a second syntax element indicating whether reference picture list information is present in the picture header, and wherein the second syntax element is pps_rpl_info_in_ph_flag.

8. The apparatus of claim 7 , wherein the format rule further specifies that the value of the first certain information in the slice header for the video slice indicates that the collocated picture used for the temporal motion vector prediction is derived from the reference list 0 each time the slice type of the video slice is P, the value of the first syntax element in the picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture and the value of the second syntax element indicates that the reference picture list information is present in the picture header.

9. The apparatus of claim 7 , wherein the format rule further specifies that a value of a third syntax element in the slice header of the video slice, which specifies a reference index of the collocated picture used for the temporal motion vector prediction, is in a range of 0 to a maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is P and the temporal motion vector prediction is enabled.

10. The apparatus of claim 7 , wherein the format rule further specifies that a value of a third syntax element in the slice header of the video slice, which specifies a reference index of the collocated picture used for the temporal motion vector prediction, refers to an entry in the reference list 0 and is in a range of 0 to a maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is B and the value of the first certain information in the slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from the reference list 0.

11. A non-transitory computer-readable storage medium storing instructions that cause a processor to:

perform a conversion between a video comprising a video picture that includes a video slice and a bitstream of the video;

wherein the bitstream conforms to a format rule;

wherein the format rule specifies that a value of first certain information in a slice header for the video slice indicates a collocated picture used for a temporal motion vector prediction is derived from a reference list 0 each time a slice type of the video slice is P and a value of a first syntax element in a picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture; and

wherein the format rule further specifies whether the value of the first certain information in the slice header for the video slice is inherited from the picture header for the video picture is determined at least based on the slice type of the video slice and a value of a second syntax element indicating whether reference picture list information is present in the picture header, and wherein the second syntax element is pps_rpl_info_in_ph_flag.

12. The non-transitory computer-readable storage medium of claim 11 , wherein the format rule further specifies that the value of the first certain information in the slice header for the video slice indicates that the collocated picture used for the temporal motion vector prediction is derived from the reference list 0 each time the slice type of the video slice is P, the value of the first syntax element in the picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture and the value of the second syntax element indicates that the reference picture list information is present in the picture header.

13. The non-transitory computer-readable storage medium of claim 11 , wherein the format rule further specifies that a value of a third syntax element in the slice header of the video slice, which specifies a reference index of the collocated picture used for the temporal motion vector prediction, is in a range of 0 to a maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is P and the temporal motion vector prediction is enabled.

14. The non-transitory computer-readable storage medium of claim 11 , wherein the format rule further specifies that a value of a third syntax element in the slice header of the video slice, which specifies a reference index of the collocated picture used for the temporal motion vector prediction, refers to an entry in the reference list 0 and is in a range of 0 to a maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is B and the value of the first certain information in the slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from the reference list 0.

15. A method for storing a bitstream of a video, comprising:

generating the bitstream of the video comprising a video picture that includes a video slice, and

storing the bitstream in a non-transitory computer-readable recording medium,

wherein the bitstream conforms to a format rule;

wherein the format rule specifies that a value of first certain information in a slice header for the video slice indicates a collocated picture used for a temporal motion vector prediction is derived from a reference list 0 each time a slice type of the video slice is P and a value of a first syntax element in a picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture; and

wherein the format rule further specifies whether the value of the first certain information in the slice header for the video slice is inherited from the picture header for the video picture is determined at least based on the slice type of the video slice and a value of a second syntax element indicating whether reference picture list information is present in the picture header, and wherein the second syntax element is pps_rpl_info_in_ph_flag.

16. The method of claim 15 , wherein the format rule further specifies that the value of the first certain information in the slice header for the video slice indicates that the collocated picture used for the temporal motion vector prediction is derived from the reference list 0 each time the slice type of the video slice is P, the value of the first syntax element in the picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture and the value of the second syntax element indicates that the reference picture list information is present in the picture header.

17. The method of claim 15 , wherein the format rule further specifies that a value of a third syntax element in the slice header of the video slice, which specifies a reference index of the collocated picture used for the temporal motion vector prediction, is in a range of 0 to a maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is P and the temporal motion vector prediction is enabled; or wherein the format rule further specifies that the value of the third syntax element in the slice header of the video slice, which specifies the reference index of the collocated picture used for the temporal motion vector prediction, refers to an entry in the reference list 0 and is in the range of 0 to the maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is B and the value of the first certain information in the slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from the reference list 0.