Methods of video picture coding with sub-block merge simplification and related apparatuses

1. A method for temporal motion vector prediction of a current picture in a series of pictures of a video sequence, the method comprising:

determining, for a current block of the current picture, whether any one of: left, top, top-right and left-bottom spatial neighboring blocks of the current block in the current picture uses a collocated picture that is collocated relative to the current picture as a reference picture;

wherein, when the determination is that one of the left, top, top-right and left-bottom spatial neighboring block uses the collocated picture as a reference picture, using a motion vector of the one of the spatial neighboring blocks as a temporal vector of the current block to identify a corresponding block in the collocated picture to be used for generating a motion vector for the current block; and

wherein, when the determination is that none of the left, top, top-right and left-bottom spatial neighboring blocks of the current block in the current picture uses a collocated picture as a reference picture, determining that the motion vectors from the spatial neighboring blocks of the current block are invalid for prediction of the temporal vector;

wherein the determining whether any one of: left, top, top-right and left-bottom spatial neighboring blocks of the current block in the current picture uses a collocated picture as a reference picture is performed for a single spatial neighboring block of the current block in the current picture; and

wherein the single spatial neighboring block is a left neighboring block of the current block in the current picture.

2. The method of claim 1 , wherein the method is performed by a video decoder.

3. The method of claim 1 , wherein the method is performed by a video encoder.

4. A device for temporal motion vector prediction of a current picture in a series of pictures of a video sequence, the device comprising:

a processor; and

a memory coupled to the processor, wherein the memory stores instructions tat when executed by the processor causes the processor to perform operations according to claim 1 .

5. A device for temporal motion vector prediction of a current picture in a series of pictures of a video sequence, configured to:

determine, for a current block of the current picture, whether any one of: left, top, top-right and left-bottom spatial neighboring blocks of the current block in the current picture uses a collocated picture that is collocated relative to the current picture as a reference picture;

wherein, when the determination is that one of the left, top, top-right and left-bottom spatial neighboring block uses the collocated picture as a reference picture, use a motion vector of the one of the spatial neighboring blocks as a temporal vector of the current block to identify a corresponding block in the collocated picture to be used for generating a motion vector for the current block; and

wherein, when the determination is that none of the left, top, top-right and left-bottom spatial neighboring blocks of the current block in the current picture uses a collocated picture as a reference picture, determine that the motion vectors from the spatial neighboring blocks of the current block are invalid for prediction of the temporal vectors;

wherein the device is further configured to perform the determination for only a single spatial neighboring block of the current block in the current picture; and

wherein the single spatial neighboring block is a left neighboring block of the current block in the current picture.

6. The device according to claim 5 wherein the device is a video decoder.

7. The device according to claim 5 wherein the device is a video encoder.

8. A network node comprising the device according to claim 5 .