Method and apparatus of constrained overlapped block motion compensation in video coding
Method and apparatus of using an Inter coding tool and OBMC (Overlapped Block Motion Compensation) are disclosed. According to one method, when the neighboring block is bi-prediction coded, the neighboring block is treated as a uni-prediction block by deriving an associated OBMC predictor based on uni-prediction motion information derived from the neighboring block. According to another method, when OBMC is applied depending on one or more constraints, an OBMC syntax is signaled conditionally at the encoder side or the OBMC syntax is parsed conditionally at the decoder side for the current block, where the OBMC syntax indicates whether the OBMC is applied to the current block.
1. A method of video coding using OBMC (Overlapped Block Motion Compensation), the method comprising:
receiving input data associated with a current block, wherein the input data correspond to pixel data to be coded at an encoder side or coded data to be decoded at a decoder side;
determining prediction direction of the current block and a neighboring block, wherein the neighboring block is encoded or decoded prior to the current block;
when the current block, the neighboring block or both are bi-prediction coded:
determining a first predictor for a target boundary area in a current reference block using a uni-prediction mode based on first motion information of the current block, wherein the current reference block is determined according to a first location of the current block and the first motion information of the current block;
determining a second predictor for the target boundary area using the uni-prediction mode based on second motion information of the neighboring block, wherein the target boundary area is adjacent to a block boundary between the current reference block and a neighboring reference block, and wherein the neighboring reference block is determined according to a second location of the neighboring block and the second motion information of the neighboring block;
generating a combined predictor using a weighted sum of the first predictor and the second predictor; and
encoding or decoding the current block using an overlapped-boundary predictor comprising the combined predictor.
2. The method of claim 1 , wherein the second predictor for the target boundary area is derived using the uni-prediction mode by treating the neighboring block as uni-prediction coded during OBMC derivation when the current block is uni-prediction coded and the neighboring block is bi-prediction coded.
3. The method of claim 2 , wherein third motion information associated with the second predictor in the uni-prediction mode is derived from the second motion information of the neighboring block.
4. The method of claim 1 , wherein when the neighboring block is bi-prediction coded, the neighboring block is treated as uni-prediction coded by selecting a target predictor from two predictors associated with the neighboring block, and wherein the target predictor is derived from a target reference picture having a smaller POC (Picture Order Count) difference to a current picture containing the current block.
5. The method of claim 1 , wherein when the neighboring block is bi-prediction coded, the neighboring block is treated as uni-prediction coded by selecting a target predictor from two predictors associated with the neighboring block, and wherein the target predictor is derived from a target reference picture having a larger POC (Picture Order Count) difference to a current picture containing the current block.
6. The method of claim 1 , wherein when the neighboring block is bi-prediction coded, the neighboring block is treated as uni-prediction coded by selecting a target predictor from two predictors associated with the neighboring block, and wherein the target predictor is assigned a larger weight for bi-prediction with different weights.
7. The method of claim 1 , wherein when the neighboring block is bi-prediction coded, the neighboring block is treated as uni-prediction coded by selecting a target predictor from two predictors associated with the neighboring block, and wherein the target predictor is derived from a target reference picture having a smaller reference picture index.
8. The method of claim 1 , wherein when the neighboring block is bi-prediction coded, the neighboring block is treated as uni-prediction coded by selecting a target predictor from two predictors associated with the neighboring block, and wherein the target predictor is derived from a target reference picture having a larger reference picture index.
9. The method of claim 1 , wherein when the neighboring block is bi-prediction coded, the neighboring block is treated as uni-prediction coded by selecting a target predictor from two predictors associated with the neighboring block, and wherein the target predictor is derived using a candidate list containing a target motion vector more similar to a current motion vector of the current block.
10. The method of claim 1 , wherein when the neighboring block is bi-prediction coded, the neighboring block is treated as uni-prediction coded by selecting a target predictor from two predictors associated with the neighboring block, and wherein the target predictor is derived using a candidate list containing a target motion vector less similar to a current motion vector of the current block.
11. The method of claim 1 , wherein the current block corresponds to a coding unit (CU) or a sub-CU.
12. An apparatus of video coding using OBMC (Overlapped Block Motion Compensation), the apparatus of video coding comprising one or more electronic circuits or processors arranged to:
receive input data associated with a current block, wherein the input data correspond to pixel data to be coded at an encoder side or coded data to be decoded at a decoder side;
determine prediction direction of the current block and a neighboring block, wherein the neighboring block is encoded or decoded prior to the current block;
when the current block, the neighboring block or both are bi-prediction coded:
determine a first predictor for a target boundary area in a current reference block using a uni-prediction mode based on first motion information of the current block, wherein the current reference block is determined according to a first location of the current block and the first motion information of the current block;
determine a second predictor for the target boundary area using the uni-prediction mode based on second motion information of the neighboring block, wherein the target boundary area is adjacent to a block boundary between the current reference block and a neighboring reference block, and wherein the neighboring reference block is determined according to a second location of the neighboring block and the second motion information of the neighboring block;
generate a combined predictor using a weighted sum of the first predictor and the second predictor; and
encode or decode the current block using an overlapped-boundary predictor comprising the combined predictor.