Slice level signaling in video bitstreams that include subpictures

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:

• partition, for a conversion between a current video block of a picture of a video and a bitstream of the video, the picture into one or more slices and into one or more sub-pictures according to a requirement of bitstream conformance;
• and
• perform the conversion at least based on the partitioning,
• wherein the requirement of bitstream conformance specifies that a union of the one or more slices covers a whole picture, and a tile of the picture overlaps with at most one sub-picture of the picture;
• and
• wherein a first syntax element is included in the bitstream to indicate whether the one or more slices have a rectangular shape.

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

• partition, for a conversion between a current video block of a picture of a video and a bitstream of the video, the picture into one or more slices and into one or more sub-pictures according to a requirement of bitstream conformance;
• and
• perform the conversion at least based on the partitioning,
• wherein the requirement of bitstream conformance specifies that a union of the one or more slices covers a whole picture, and a tile of the picture overlaps with at most one sub-picture of the picture;
• and
• wherein a first syntax element is included in the bitstream to indicate whether the one or more slices have a rectangular shape.

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:

• partitioning, for a current video block of a picture of a video, the picture into one or more slices and into one or more sub-pictures according to a requirement of bitstream conformance;
• and
• generating the bitstream at least based on the partitioning, and
• wherein the requirement of bitstream conformance specifies that a union of the one or more slices covers a whole picture, and a tile of the picture overlaps with at most one sub-picture of the picture;
• and
• wherein a first syntax element is included in the bitstream to indicate whether the one or more slices have a rectangular shape.