Method and apparatus of signaling subpicture information in video coding
Methods and apparatus for video coding are disclosed. According to one method, a bitstream is generated or received, where the bitstream includes a first syntax and a second syntax. The first syntax is related to a target number of bits used to represent a set of third syntaxes and each third syntax specifies one subpicture ID for one subpicture in a set of subpictures. The second syntax is related to a total number of subpictures in the set of subpicture, where a first number that can be represented by the target number of bits is equal to or greater than the total number of subpictures. According to another method, the subpicture ID syntaxes have different values for different subpictures.
1. A method for coding a video sequence, wherein a subpicture coding mode is included, the method comprising:
generating, at an encoder side, or receiving, at a decoder side, a bitstream corresponding to encoded data of the video sequence, wherein the bitstream comprises a first syntax and a second syntax, the first syntax corresponds to a target number of bits used to represent a set of third syntaxes and each third syntax specifies one subpicture ID for one subpicture in a set of subpictures, and the second syntax corresponds to a total number of subpictures in the set of subpicture, and wherein a computation made to a first value of the first syntax is equal to or greater than a second value of the second syntax; and
encoding, at the encoder side, or decoding, at the decoder side, the video sequence based on information comprising the set of subpictures,
wherein the first value of the first syntax is the target number of bits minus 1,
wherein the computation made to the first value of the first syntax corresponds to (1<<((the target number of bits minus 1)+1), and wherein “<<” represents an arithmetic left shift operation.
2. The method of claim 1 , wherein the first syntax and the second syntax are signaled, at the encoder side, or parsed, at the decoder side, in sequence parameter set (SPS).
3. The method of claim 1 , wherein the first syntax and the second syntax are signaled, at the encoder side, or parsed, at the decoder side, in sequence parameter set (SPS), picture parameter set (PPS), slice header (SH), picture header (PH) or a combination thereof.
4. The method of claim 1 , wherein the first syntax is in sequence parameter set (SPS) and designated as sps_subpic_id_len_minus1 for representing the target number of bits minus 1.
5. The method of claim 1 , wherein the second syntax is in sequence parameter set (SPS) and designated as sps_num_subpic_minus1 for representing the total number of subpictures in the set of subpicture minus 1.
6. The method of claim 1 , wherein the first syntax corresponds to the target number of bits minus an offset and plus a first value, and wherein the first value corresponds to Ceil(Log 2 (the total number of subpictures)), and wherein “Ceil” is a ceiling function and “Log 2” is a log-base-2 function.
7. The method of claim 1 , wherein the bitstream satisfies a bitstream conformance requirement that the first number is equal to or greater than the total number of subpictures.
8. An apparatus for coding a video sequence, wherein a subpicture coding mode is included, the apparatus comprising one or more electronic circuits or processors arranged to:
generate, at an encoder side, or receive, at a decoder side, a bitstream corresponding to encoded data of the video sequence, wherein the bitstream comprises a first syntax and a second syntax, the first syntax corresponds to a target number of bits used to represent a set of third syntaxes and each third syntax specifies one subpicture ID for one subpicture in a set of subpictures, and the second syntax corresponds to a total number of subpictures in the set of subpicture, and wherein a computation made to a first value of the first syntax is equal to or greater than a second value of the second syntax; and
encode, at the encoder side, or decode, at the decoder side, the video sequence based on information comprising the set of subpictures,
wherein the first value of the first syntax is the target number of bits minus 1,
wherein the computation made to the first value of the first syntax corresponds to (1<<((the target number of bits minus 1)+1), and wherein “<<” represents an arithmetic left shift operation.