Method and apparatus for video coding
An apparatus for video decoding includes receiving circuitry and processing circuitry. In some examples, processing circuitry determines a parameter based on prediction information decoded from a coded video bitstream. The parameter is in a range that depends on a flag indicative of an enabler disable status of subblock based temporal motion vector prediction. Then, the processing circuitry calculates the maximum number of candidates in the subblock based merge candidate lists based on the parameter, and reconstructs, m response to a current block in a subblock based prediction mode, samples of the current block based on a candidate selection from a constructed subblock based merge candidate list of the current block. The constructed subblock based merge candidate list of the current block is constrained by the maximum number.
1. A method for video decoding in a decoder, comprising:
determining, by a processor, a parameter based on prediction information decoded from a coded video bitstream;
calculating, by the processor, a maximum number of candidates in subblock based merge candidate lists based on the parameter, the parameter being in a range from 0 to 5-sps_sbtmvp_enabled_flag, wherein the sps_sbtmvp_enabled_flag equal to 1 specifies that subblock based temporal motion vector predictors are used in decoding of pictures with slices having slice type not equal to I (intra coded) in a coded video, and wherein the sps_sbtmvp_enabled_flag equal to 0 specifies that the subblock based temporal motion vector predictors are not used in the coded video; and
reconstructing, in response to a current block in a subblock based prediction mode, samples of the current block based on a candidate selection from a constructed subblock based merge candidate list of the current block, the constructed subblock based merge candidate list of the current block being constrained by the maximum number of candidates in the subblock based merge candidate lists.
2. The method of claim 1 , further comprising:
calculating the maximum number of candidates in the subblock based merge candidate lists by subtracting the parameter from a default number.
3. The method of claim 2 , wherein the default number is 5.
4. The method of claim 1 , further comprising:
receiving the parameter that is signaled in the coded video bitstream.
5. The method of claim 1 , further comprising:
inferring the parameter based on a default number and the sps_sbtmvp_enabled_flag in response to the parameter not being signaled in the coded video bitstream.
6. The method of claim 1 , wherein the sps_sbtmvp_enabled_flag is at a sequence parameter set (SPS) level.
7. The method of claim 1 , wherein the parameter is in the range that is determined based on the sps_sbtmvp_enabled_flag at a sequence parameter set (SPS) level and a flag indicative of an enable/disable status of temporal motion vector prediction at a picture header (PH) level.
8. The method of claim 7 , further comprising:
inferring the parameter based on a default number, the sps_sbtmvp_enabled_flag at the SPS level, and the flag indicative of the enable/disable status of temporal motion vector prediction at the PH level in response to the parameter not being signaled in the coded video bitstream.
9. An apparatus for video decoding, comprising:
processing circuitry configured to:
determine a parameter based on prediction information decoded from a coded video bitstream;
calculate a maximum number of candidates in subblock based merge candidate lists based on the parameter, the parameter being in a range from 0 to 5-sps_sbtmvp_enabled_flag, wherein the sps_sbtmvp_enabled_flag equal to 1 specifies that subblock based temporal motion vector predictors are used in decoding of pictures with slices having slice type not equal to I (intra coded) in a coded video, and wherein the sps_sbtmvp_enabled_flag equal to 0 specifies that the subblock based temporal motion vector predictors are not used in the coded video; and
reconstruct, in response to a current block in a subblock based prediction mode, samples of the current block based on a candidate selection from a constructed subblock based merge candidate list of the current block, the constructed subblock based merge candidate list of the current block being constrained by the maximum number of candidates in the subblock based merge candidate lists.
10. The apparatus of claim 9 , wherein the processing circuitry is further configured to:
calculate the maximum number of candidates in the subblock based merge candidate lists by subtracting the parameter from a default number.
11. The apparatus of claim 10 , wherein the default number is 5.
12. The apparatus of claim 9 , wherein the processing circuitry is configured to
receive the parameter that is signaled in the coded video bitstream.
13. The apparatus of claim 9 , wherein the processing circuitry is configured to:
infer the parameter based on a default number and the sps_sbtmvp_enabled_flag in response to the parameter not being signaled in the coded video bitstream.
14. The apparatus of claim 9 , wherein the sps_sbtmvp_enabled_flag is at a sequence parameter set (SPS) level.
15. The apparatus of claim 9 , wherein the parameter is in the range that is determined based on the sps_sbtmvp_enabled_flag at a sequence parameter set (SPS) level and a flag indicative of an enable/disable status of temporal motion vector prediction at a picture header (PH) level.
16. The apparatus of claim 15 , wherein the processing circuitry is configured to:
infer the parameter based on a default number, the sps_sbfmvp_enabled_flag at the SPS level, and the second flag indicative of the enable/disable status of temporal motion vector prediction at the PH level in response to the parameter not being signaled in the coded video bitstream.
17. A non-transitory computer-readable medium storing instructions which when executed by a computer for video decoding cause the computer to perform:
determining a parameter based on prediction information decoded from a coded video bitstream;
calculating a maximum number of candidates in subblock based merge candidate lists based on the parameter, the parameter being in a range from 0 to 5-sps_sbfmvp_enabled_flag, wherein the sps_sbtmvp_enabled_flag equal to 1 specifies that subblock based temporal motion vector predictors are used in decoding of pictures with slices having slice type not equal to I (intra coded) in a coded video, and wherein the sps_sbtmvp_enabled_flag equal to 0 specifies that the subblock based temporal motion vector predictors are not used in the coded video; and
reconstructing, in response to a current block in a subblock based prediction mode, samples of the current block based on a candidate selection from a constructed subblock based merge candidate list of the current block, the constructed subblock based merge candidate list of the current block being constrained by the maximum number of candidates in the subblock based merge candidate lists.
18. The non-transitory computer-readable medium of claim 17 , wherein parameter is signaled in the coded video bitstream.
19. The non-transitory computer-readable medium of claim 17 , wherein the parameter is in the range that is determined based on the sps_sbtmvp_enabled_flag at a sequence parameter set (SPS) level and a flag indicative of an enable/disable status of temporal motion vector prediction at a picture header (PH) level.