Methods and apparatus for reducing the coding latency of decoder-side motion refinement
Embodiments of video coding systems and methods are described for reducing coding latency introduced by decoder-side motion vector refinement (DMVR). In one example, two non-refined motion vectors are identified for coding of a first block of samples (e.g. a first coding unit) using bi-prediction. One or both of the non-refined motion vectors are used to predict motion information for a second block of samples (e.g. a second coding unit). The two non-refined motion vectors are refined using DMVR, and the refined motion vectors are used to generate a prediction signal of the first block of samples. Such embodiments allow the second block of samples to be coded substantially in parallel with the first block without waiting for completion of DMVR on the first block. In additional embodiments, optical-flow-based techniques are described for motion vector refinement.
1. A video decoding method comprising:
identifying at least one non-refined motion vector associated with a first block in a picture;
refining the at least one non-refined motion vector to generate at least one refined motion vector associated with the first block;
for a second block in the picture neighboring the first block, determining whether the second block is in a different segment of the picture from the first block;
predicting motion information of the second block, wherein, in response to a determination that the second block is in the same segment of the picture as the first block, the at least one refined motion vector is used as a predictor of the motion information of the second block; and
predicting the second block based on the predicted motion information.
2. The method of claim 1 , further comprising predicting the first block based on the at least one refined motion vector.
3. The method of claim 1 , wherein the refining is performed using decoder-side motion vector refinement (DMVR).
4. The method of claim 1 , further comprising:
for a third block in the picture neighboring the first block, determining whether the third block is in a different segment of the picture from the first block;
predicting motion information of the third block, wherein, in response to a determination that the third block is in a different segment of the picture from the first block, the non-refined motion vector and the refined motion vector are not used as predictors of the motion information of the third block.
5. A video decoding apparatus comprising one or more processors configured to perform at least:
identifying at least one non-refined motion vector associated with a first block in a picture;
refining the at least one non-refined motion vector to generate at least one refined motion vector associated with the first block;
for a second block in the picture neighboring the first block, determining whether the second block is in a different segment of the picture from the first block;
predicting motion information of the second block, wherein, in response to a determination that the second block is in the same segment of the picture as the first block, the at least one refined motion vector is used as a predictor of the motion information of the second block; and
predicting the second block based on the predicted motion information.
6. The apparatus of claim 5 , further configured to predict the first block based on the at least one refined motion vector.
7. The apparatus of claim 5 , wherein the second block is predicted using bi-prediction.
8. The apparatus of claim 5 , further configured to perform:
for a third block in the picture neighboring the first block, determining whether the third block is in a different segment of the picture from the first block;
predicting motion information of the third block, wherein, in response to a determination that the third block is in a different segment of the picture from the first block, the non-refined motion vector and the refined motion vector are not used as predictors of the motion information of the third block.
9. A video encoding method comprising:
identifying at least one non-refined motion vector associated with a first block in a picture;
refining the at least one non-refined motion vector to generate at least one refined motion vector associated with the first block;
for a second block in the picture neighboring the first block, determining whether the second block is in a different segment of the picture from the first block;
predicting motion information of the second block, wherein, in response to a determination that the second block is in the same segment of the picture as the first block, the at least one refined motion vector is used as a predictor of the motion information of the second block; and
predicting the second block based on the predicted motion information.
10. The method of claim 9 , further comprising predicting the first block based on the at least one refined motion vector.
11. The method of claim 9 , further comprising signaling in a bitstream information indicating an arrangement of segments in the picture.
12. The method of claim 9 , further comprising:
for a third block in the picture neighboring the first block, determining whether the third block is in a different segment of the picture from the first block;
predicting motion information of the third block, wherein, in response to a determination that the third block is in a different segment of the picture from the first block, the non-refined motion vector and the refined motion vector are not used as predictors of the motion information of the third block.
13. A video encoding apparatus comprising one or more processors configured to perform at least:
identifying at least one non-refined motion vector associated with a first block in a picture;
refining the at least one non-refined motion vector to generate at least one refined motion vector associated with the first block;
for a second block in the picture neighboring the first block, determining whether the second block is in a different segment of the picture from the first block;
predicting motion information of the second block, wherein, in response to a determination that the second block is in the same segment of the picture as the first block, the at least one refined motion vector is used as a predictor of the motion information of the second block; and
predicting the second block based on the predicted motion information.
14. The apparatus of claim 13 , further configured to predict the first block based on the at least one refined motion vector.
15. The apparatus of claim 13 , further comprising signaling in a bitstream an index associated with the second block, the index indicating that the motion information of the second block is predicted based on the first block.
16. The apparatus of claim 13 , further configured to perform:
for a third block in the picture neighboring the first block, determining whether the third block is in a different segment of the picture from the first block;
predicting motion information of the third block, wherein, in response to a determination that the third block is in a different segment of the picture from the first block, the non-refined motion vector and the refined motion vector are not used as predictors of the motion information of the third block.