Bl-prediction for video coding
Systems, methods, and instrumentalities may be provided for determining whether to bypass bi-directional optical flow (BDOF) if BDOF is used in combination with bi-prediction with coding unit (CU) weights (e.g., generalized bi-prediction (GBi)). A coding system may combine coding modes, coding techniques, and/or coding tools. The coding system may include a wireless transmit/receive unit (WTRU). For example, the coding system may combine BDOF and bi-prediction with GU weights (BCW). BDOF may include refining a motion vector associated with a current CU based at least in part on gradients associated with a location in the current CU. The coding system may determine that BDOF is enabled, and/or that bi-prediction with CU weights is enabled for the current CU. The coding system's determination that bi-prediction with CU weights is enabled and/or that BDOF is enabled may be based on one or more indications.
1. An apparatus for video processing, comprising:
a processor configured to:
determine that bi-directional optical flow (BDOF) is enabled;
determine that bi-prediction with coding unit (CU) weights is enabled for a current coding block;
identify a weight indication of bi-prediction with CU weights for the current coding block, wherein the weight indication indicates whether a first weight to be applied to a first prediction sample value for the current coding block in bi-prediction with CU weights is equal to a second weight to be applied to a second prediction sample value for the current coding block in bi-prediction with CU weights;
determine whether to bypass BDOF for the current coding block based at least in part on the weight indication of bi-prediction with CU weights for the current coding block, wherein, based on a condition that the first weight to be applied to the first prediction sample value for the current coding block in bi-prediction with CU weights is not equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, BDOF is determined to be bypassed for the current coding block; and
reconstruct the current coding block based on the determination of whether to bypass BDOF for the current coding block.
2. The apparatus of claim 1 , wherein the processor is further configured to, based on a condition that the first weight to be applied to the first prediction sample value for the current coding block in bi-prediction with CU weights is equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, determine whether to perform BDOF for the current coding block based on at least another condition.
3. The apparatus of claim 1 , wherein the weight indication of bi-prediction with CU weights for the current coding block comprises an index value corresponding to a predetermined weight.
4. The apparatus of claim 1 , wherein the weight indication indicates that the first weight to be applied to the first prediction sample value in bi-prediction with CU weights is not equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, and the processor is further configured to:
determine the first prediction CU weight to be applied to the first prediction sample value in bi-prediction with CU weights based on the weight indication;
obtain the second weight based on the first weight and a constraint; and
perform bi-prediction with CU weights on the current coding block based on the first weight and the second weight.
5. The apparatus of claim 1 , wherein the weight indication indicates that the first weight to be applied to the first prediction sample value in bi-prediction with CU weights is equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, and the processor is further configured to determine to perform BDOF for the current coding block, wherein BDOF comprises refining a motion vector associated with the current coding block based at least in part on gradients associated with a location in the current coding block.
6. The apparatus of claim 1 , wherein the processor is further configured to perform bi-prediction with CU weights without BDOF based on the determination to bypass BDOF, to reconstruct the current coding block.
7. A method for video processing, comprising:
determining that bi-directional optical flow (BDOF) is enabled;
determining that bi-prediction with coding unit (CU) weights is enabled for a current coding block;
identifying a weight indication of bi-prediction with CU weights for the current coding block, wherein the weight indication indicates whether a first weight to be applied to a first prediction sample value for the current coding block in bi-prediction with CU weights is equal to a second weight to be applied to a second prediction sample value for the current coding block in bi-prediction with CU weights;
determining whether to bypass BDOF for the current coding block based at least in part on the weight indication of bi-prediction with CU weights for the current coding block, wherein, based on a condition that the first weight to be applied to the first prediction sample value for the current coding block in bi-prediction with CU weights is not equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, BDOF is determined to be bypassed for the current coding block; and
reconstructing the current coding block based on the determination of whether to bypass BDOF for the current coding block.
8. The method of claim 7 , further comprising, based on a condition that the first weight to be applied to the first prediction sample value for the current coding block in bi-prediction with CU weights is equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, determining whether to perform BDOF for the current coding block based on at least another condition.
9. The method of claim 7 , wherein the weight indication of bi-prediction with CU weights for the current coding block comprises an index value corresponding to a predetermined weight.
10. The method of claim 7 , wherein the weight indication indicates that the first weight to be applied to the first prediction sample value in bi-prediction with CU weights is not equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, the method further comprising:
determining the first weight to be applied to the first prediction sample value in bi-prediction with CU weights based on the weight indication;
obtaining the second weight based on the first weight and a constraint; and
performing bi-prediction with CU weights on the current coding block based on the first weight and the second weight.
11. The method of claim 7 , wherein the weight indication indicates that the first weight to be applied to the first prediction sample value in bi-prediction with CU weights is equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, and the method further comprises determining to perform BDOF for the current coding block, wherein BDOF comprises refining a motion vector associated with the current coding block based at least in part on gradients associated with a location in the current coding block.
12. An apparatus for video processing, comprising:
a processor configured to:
determine that bi-directional optical flow (BDOF) is enabled;
determine that bi-prediction with coding unit (CU) weights is enabled for a current coding block;
generate a weight indication of bi-prediction with CU weights for the current coding block, wherein the weight indication indicates whether a first weight to be applied to a first prediction sample value for the current coding block in bi-prediction with CU weights is equal to a second weight to be applied to a second prediction sample value for the current coding block in bi-prediction with CU weights;
determine whether to bypass BDOF for the current coding block based at least in part on the weight indication of bi-prediction with CU weights for the current coding block, wherein, based on a condition that the first weight to be applied to the first prediction sample value for the current coding block in bi-prediction with CU weights is not equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, BDOF is determined to be bypassed for the current coding block;
generate residual based on the determination of whether to bypass BDOF; and
send the residual and the weight indication of bi-prediction with CU weights.
13. The apparatus of claim 12 , wherein the processor is further configured to, based on a condition that the first weight to be applied to the first prediction sample value for the current coding block in bi-prediction with CU weights is equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, determine whether to perform BDOF for the current coding block based on at least another condition.
14. The apparatus of claim 12 , wherein the weight indication of bi-prediction with CU weights for the current coding block comprises an index value corresponding to a predetermined weight.
15. The apparatus of claim 12 , wherein the weight indication indicates that the first weight to be applied to the first prediction sample value in bi-prediction with CU weights is not equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, and the processor is further configured to:
determine the first weight to be applied to the first prediction sample value in bi-prediction with CU weights based on the weight indication;
obtain the second weight based on the first weight and a constraint; and
perform bi-prediction with CU weights on the current coding block based on the first weight and the second weight.
16. A method for video processing, comprising:
determining that bi-directional optical flow (BDOF) is enabled;
determining that bi-prediction with coding unit (CU) weights is enabled for a current coding block;
generating a weight indication of bi-prediction with CU weights for the current coding block, wherein the weight indication indicates whether a first weight to be applied to a first prediction sample value for the current coding block in bi-prediction with CU weights is equal to a second weight to be applied to a second prediction sample value for the current coding block in bi-prediction with CU weights;
determining whether to bypass BDOF for the current coding block based at least in part on the weight indication of bi-prediction with CU weights for the current coding block, wherein, based on a condition that the first weight to be applied to the first prediction sample value for the current coding block in bi-prediction with CU weights is not equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, BDOF is determined to be bypassed for the current coding block;
generating residual based on the determination of whether to bypass BDOF; and
sending the residual and the weight indication of bi-prediction with CU weights.
17. The method of claim 16 , further comprising, based on a condition that the first weight to be applied to the first prediction sample value for the current coding block in bi-prediction with CU weights is equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, determining whether to perform BDOF for the current coding block based on at least another condition.
18. The method of claim 16 , wherein the weight indication indicates that the first weight to be applied to the first prediction sample value in bi-prediction with CU weights is equal to the second weight to be applied to the second prediction sample value for the current coding block in bi-prediction with CU weights, and the method further comprises determining to perform BDOF for the current coding block, wherein BDOF comprises refining a motion vector associated with the current coding block based at least in part on gradients associated with a location in the current coding block.
19. The apparatus of claim 1 , wherein the first prediction sample value is associated with a first reference picture, and the second prediction sample value is associated with a second reference picture, wherein the first reference picture and first reference picture are different.
20. A computer-readable medium including instructions, which, when executed by one or more processors, cause the one or more processors to perform the method of claim 7 .