Improved context derivation for motion vector difference coding

Abstract

The present disclosure relates to encoding and decoding of motion vector difference for inter predicting video blocks. An example for decoding an inter predicted video block of a video stream is disclosed. The method includes: deriving a motion vector prediction mode for a video block; deriving a context for signaling a set of syntax elements associated with a motion vector difference (MVD) associated with the video block based on the inter prediction mode and / or the motion vector prediction mode from the video stream; and decoding the video block based on the set of syntax elements and the derived context.

Claims

1. A method for decoding a video block in a video stream, which is performed by a decoder, the method is: The steps include receiving the aforementioned video stream, The steps include determining the interprediction mode of the video block from the video stream, The steps include determining the motion vector prediction mode of the video block, A step of deriving a context from the video stream for signaling a set of syntax elements associated with a motion vector difference (MVD) associated with the video block, based on at least one of the inter-prediction mode and the motion vector prediction mode, wherein the set of syntax elements associated with the MVD is: The mv_joint syntax element represents the non-zero components of the aforementioned MVD, The mv_sign syntax element indicates whether the aforementioned MVD is positive, The MVD class of the aforementioned MVD is represented by the mv_class syntax element, The mv_bit syntax element represents the corresponding integer part of the offset between the MVD and the starting size of the MVD class, The mv_fr syntax element represents the first two fractional bits of the aforementioned MVD, The mv_hp syntax element represents the third fractional bit of the aforementioned MVD, and A step including at least one of the following, A step of decoding the video block based on the set of syntax elements and the derived context. Methods that include...

2. The method according to claim 1, wherein the video block includes one of a coded block, a prediction block, or a coding unit.

3. The method according to claim 1, wherein the interpretation mode indicates whether one motion vector difference or multiple motion vector differences are signaled to a single interpretation reference frame list or to both of two interpretation reference frame lists.

4. The step of deriving the context for signaling the set of syntax elements associated with the MVD associated with the video block is: The steps include: deriving the context as a first predefined context in response to the signaling of the MVD to the single interpredictive reference framelist; The step of deriving the context as a second predefined context in response to the MVD being signaled to both of the two interpredictive reference framelists, The first predefined context and the second predefined context are different, The method according to claim 3.

5. The method according to claim 1, wherein the inter-prediction mode includes one of a single reference inter-prediction mode or a composite reference inter-prediction mode.

6. The method according to claim 5, wherein the step of deriving the context includes the step of deriving the context for signaling the set of syntax elements associated with the MVD associated with the video block, based at least on the interprediction mode.

7. The step of deriving the context for signaling the set of syntax elements associated with the MVD associated with the video block is: In response to the inter-prediction mode being the single reference inter-prediction mode, the step of deriving the context as a first predefined context, The step of deriving the context as a second predefined context in response to the interpretation mode being the composite reference interpretation mode, The first predefined context and the second predefined context are different, The method according to claim 6.

8. In the case of the single reference interpretation mode, the motion vector prediction mode includes one of the following: direct merge motion vector prediction mode (NEARMV), merge mode motion vector difference prediction mode (NEWMV), and global motion vector prediction mode (GLOBALMV), associated with a single interpretation reference frame of the video block. In the case of the composite reference interpretation mode having two reference interpretation prediction frames, the motion vector prediction mode is: The direct merge motion vector prediction mode for the first reference interpretation frame of the two reference interpretation prediction frames and the merge mode motion vector difference prediction mode (NEAR_NEWMV) for the second reference interpretation prediction frame of the two reference interpretation prediction frames, The direct merge motion vector prediction mode for the second reference interpretation frame of the two reference interpretation prediction frames and the merge mode motion vector difference prediction mode (NEW_NEARMV) for the first reference interpretation prediction frame of the two reference interpretation prediction frames, The merge mode motion vector difference prediction mode (NEW_NEWMV) for both the first and second reference inter prediction frames of the two reference inter prediction frames, The global motion vector prediction mode (GLOBAL_GLOBALMV) for both the first and second reference interpretation frames of the two reference interpretation prediction frames and Including one of the following, The method according to claim 5.

9. The step of deriving the context for signaling the set of syntax elements associated with the MVD associated with the video block is: The steps include: deriving the context as a first predefined context in response to the motion vector prediction mode being NEWMV or NEW_NEWMV; The step of deriving the context as a second predefined context in response to the fact that the motion vector prediction mode is neither NEWMV nor NEW_NEWMV, The first predefined context and the second predefined context are different, The method according to claim 8.

10. The method according to claim 9, wherein the first predefined context and the second predefined context are configured to signal one of the mv_joint syntax for indicating the non-zero components of the MVD.

11. The method according to claim 8, wherein the interpretation mode includes the composite reference interpretation mode, and the step of deriving the context includes the step of deriving the context for signaling the set of syntax elements associated with the MVD associated with the video block, based at least on whether the motion vector prediction mode is one of NEW_NEARMV or NEAR_NEWMV.

12. The step of deriving the context for signaling the set of syntax elements associated with the MVD associated with the video block is: The steps include: deriving the context as a first predefined context in response to the motion vector prediction mode being NEW_NEARMV or NEAR_NEWMV; The step of deriving the context as a second predefined context in response to the fact that the motion vector prediction mode is neither NEW_NEARMV nor NEAR_NEWMV, The first predefined context and the second predefined context are different, The method according to claim 11.

13. The method according to claim 12, wherein the first predefined context and the second predefined context are configured to signal the mv_joint syntax for indicating non-zero MVD components.

14. The method according to claim 12, wherein the first predefined context and the second predefined context are configured to signal the mv_class syntax indicating the MVD class of the MVD.

15. A device configured to carry out the method described in any one of claims 1 to 14.

16. A computer program for performing the method described in any one of claims 1 to 14.

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