Method and apparatus for signaling subpicture partitioning information

A video processing apparatus in an encoder, comprising:

• at least one memory for storing instructions;
• and
• at least one processor configured to execute the instructions to cause the apparatus to perform:
• determining, according to a subpicture information present flag signaled in a bitstream, whether the bitstream comprises subpicture information;
• and
• in response to the bitstream comprising the subpicture information, signaling in the bitstream at least one of:
• a number of subpictures in a picture,
• a width, a height, a position, an identifier (ID) mapping of a target subpicture,
• a subpic_treated_as_pic_flag, and
• a loop_filter_across_subpic_enabled_flag,
• wherein the signaling of at least one of the width, the height, and the position of the target subpicture is based on the number of the subpictures in the picture, and
• wherein, when signaling in the bitstream, the at least one processor is configured to execute the instructions to cause the apparatus to perform:
• signaling the subpic_treated_as_pic_flag, the loop_filter_across_subpic_enabled_flag, and at least one of the width, the height, and the position of the target subpicture, wherein:
• the signaling of the at least one of the width, the height, and the position of the target subpicture is skipped when there is only one subpicture in the picture,
• the subpic_treated_as_pic_flag indicates whether a subpicture of each coded picture in a coded layer video sequence (CLVS) is treated as a picture in a decoding process excluding in-loop filtering operations, and
• the loop_filter_across_subpic_enabled_flag indicates whether in-loop filtering operations across subpicture boundaries are enabled.

A non-transitory computer readable storage medium storing a bitstream of a video for processing according to a method comprising:

• determining, according to a subpicture information present flag signaled in the bitstream, whether the bitstream comprises subpicture information;
• and
• in response to the bitstream comprising the subpicture information, signaling in the bitstream at least one of:
• a number of subpictures in a picture,
• a width, a height, a position, an identifier (ID) mapping of a target subpicture,
• a subpic_treated_as_pic_flag, and
• a loop_filter_across_subpic_enabled_flag,
• wherein the signaling of at least one of the width, the height, and the position of the target subpicture is based on the number of the subpictures in the picture, and
• wherein, when signaling in the bitstream, the set of instructions that are executable by one or more processing devices to cause the video processing apparatus to perform:
• signaling the subpic_treated_as_pic_flag, the loop_filter_across_subpic_enabled_flag, and at least one of the width, the height, and the position of the target subpicture, wherein:
• the signaling of the at least one of the width, the height, and the position of the target subpicture is skipped when there is only one subpicture in the picture,
• the subpic_treated_as_pic_flag indicates whether a subpicture of each coded picture in a coded layer video sequence (CLVS) is treated as a picture in a decoding process excluding in-loop filtering operations, and
• the loop_filter_across_subpic_enabled_flag indicates whether in-loop filtering operations across subpicture boundaries are enabled.

A non-transitory computer readable storage medium storing a bitstream, the bitstream comprising:

• a subpicture information present flag indicating that the bitstream comprises subpicture information comprising at least one of:
• a number of subpictures in a picture,
• a width, a height, a position, an identifier (ID) mapping of a target subpicture,
• a subpic_treated_as_pic_flag, and
• a loop_filter_across_subpic_enabled_flag,
• wherein whether the subpicture information comprises at least one of the width, the height, and the position of the target subpicture is determined based on the number of the subpictures in the picture,
• wherein the subpicture information comprises the subpic_treated_as_pic_flag, the loop_filter_across_subpic_enabled_flag, and at least one of the width, the height, and the position of the target subpicture when there are at least two subpictures in the picture,
• wherein the subpicture information does not comprise the at least one of the width, the height, and the position of the target subpicture when there is only one subpicture in the picture,
• wherein the subpic_treated_as_pic_flag indicates whether a subpicture of each coded picture in a coded layer video sequence (CLVS) is treated as a picture in a decoding process excluding in-loop filtering operations, and
• wherein the loop_filter_across_subpic_enabled_flag indicates whether in-loop filtering operations across subpicture boundaries are enabled.