Restrictions on decoder side motion vector derivation based on coding information

Abstract

Devices, systems and methods for digital video coding, which includes restrictions on decoder-side motion vector derivation based on coding information, are described. An exemplary method for video processing includes making a decision, for a conversion between a current block of a video and a bitstream representation of the video, regarding a selective enablement of a decoder side motion vector derivation (DMVD) tool for the current block, the DMVD tool deriving a refinement of motion information signaled in the bitstream representation, and the conversion using a merge mode and motion vector differences that are indicated by a motion direction and a motion magnitude, and performing, based on the decision, a conversion between the current block and the bitstream representation.

What is claimed is: 
     
         1 . A method for video processing, comprising:
 making a decision, for a conversion between a current block of a video and a bitstream representation of the video, regarding whether a decoder side motion vector derivation (DMVD) tool for the current block is enabled based on whether a coding mode is enabled for the conversion; wherein the DMVD tool derives a refinement of motion information, and the coding mode comprises at least one of a merge mode with a motion vector difference that is indicated by a motion direction and a motion magnitude, or a motion vector prediction mode in which a motion vector is acquired based on a motion vector predictor; and   performing, based on the decision, a conversion between the current block and the bitstream representation.   
     
     
         2 . The method of  claim 1 , wherein the conversion generates the current block from the bitstream representation. 
     
     
         3 . The method of  claim 1 , wherein the conversion generates the bitstream representation from the current block. 
     
     
         4 . The method of  claim 1 , wherein the DMVD tool comprises at least one of a bi-directional optical flow algorithm, a decoder-side motion vector refinement algorithm or a frame-rate up conversion algorithm. 
     
     
         5 . The method of  claim 1 , wherein the DMVD tool is disabled if the current block is coded using the merge mode with the motion vector difference. 
     
     
         6 . The method of  claim 1 , wherein the merge mode with the motion vector difference further comprises a starting point of motion information indicated by a merge index, and wherein a final motion information of the current block is based on the motion vector difference and the starting point. 
     
     
         7 . The method of  claim 1 , wherein the merge mode with the motion vector difference indicates that the motion vector difference comprises a non-zero motion vector difference (MVD) component. 
     
     
         8 . The method of  claim 1 , wherein the DMVD tool is disabled if the current block is coded using the motion vector prediction mode. 
     
     
         9 . The method of  claim 1 , wherein the motion vector prediction mode is an Advance motion vector predictor (AMVP) mode. 
     
     
         10 . The method of  claim 1 , wherein whether the DMVD tool for the current block is enabled is further based on whether a generalized bi-prediction (GBI) mode is enabled, wherein the GBI mode indicates that different weights in a Coding Unit level are applied to the two prediction blocks generated from a reference picture list 0 and a reference picture list 1 to derive a final prediction block of the current block. 
     
     
         11 . The method of  claim 1 , wherein the DMVD tool is disabled if the current block is coded using the GBI mode. 
     
     
         12 . The method of  claim 1 , wherein whether the DMVD tool is enabled is further based on motion information of the current video block. 
     
     
         13 . The method of  claim 12 , wherein the DMVD tool is enabled upon a determination that (1) an absolute value of a motion vector, or (2) an absolute value of a motion vector difference, or (3) an absolute value of a motion vector of the current block is (a) less than a threshold TH1, wherein TH1≥0, or (b) greater than a threshold TH2, wherein TH2≥0. 
     
     
         14 . The method of  claim 12 , wherein the DMVD tool is enabled upon a determination that an absolute value of a decoded motion vector of the current block in a horizontal or vertical prediction direction is (a) less than a threshold THh1 or THv1, respectively, wherein THh1≥0 and THv1≥0, or (b) greater than a threshold THh2 or THv2, respectively, wherein THh2≥0 and THv2≥0. 
     
     
         15 . The method of  claim 12 , wherein the DMVD tool is enabled upon a determination that a function of an absolute value of a decoded motion vector (MV) of the current block in a horizontal prediction direction (MV_x) and a vertical prediction direction (MV_y) is (a) less than a threshold TH1, wherein TH1≥0, or (b) greater than a threshold TH2, wherein TH2≥0. 
     
     
         16 . The method of  claim 12 , wherein the current block is coded using a bi-prediction mode, and wherein the decision is further based on the motion information from only one reference picture list associated with the current block. 
     
     
         17 . The method of  claim 12 , wherein the current block is coded using a bi-prediction mode, and wherein the decision is further based on the motion information from both reference picture lists associated with the current block. 
     
     
         18 . An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
 make a decision, for a conversion between a current block of a video and a bitstream representation of the video, regarding whether a decoder side motion vector derivation (DMVD) tool for the current block is enabled based on whether a coding mode is enabled for the conversion; wherein the DMVD tool derives a refinement of motion information, and the coding mode comprises at least one of a merge mode with a motion vector difference that is indicated by a motion direction and a motion magnitude, or a motion vector prediction mode in which a motion vector is acquired based on a motion vector predictor; and   perform, based on the decision, a conversion between the current block and the bitstream representation.   
     
     
         19 . A non-transitory computer-readable storage medium storing instructions that cause a processor to:
 make a decision, for a conversion between a current block of a video and a bitstream representation of the video, regarding whether a decoder side motion vector derivation (DMVD) tool for the current block is enabled based on whether a coding mode is enabled for the conversion; wherein the DMVD tool derives a refinement of motion information, and the coding mode comprises at least one of a merge mode with a motion vector difference that is indicated by a motion direction and a motion magnitude, or a motion vector prediction mode in which a motion vector is acquired based on a motion vector predictor; and   perform, based on the decision, a conversion between the current block and the bitstream representation.   
     
     
         20 . A non-transitory computer-readable recording medium storing a bitstream representation which is generated by a method performed by a video processing apparatus, wherein the method comprises:
 making a decision for a current block regarding whether a decoder side motion vector derivation (DMVD) tool for the current block is enabled based on whether a coding mode is enabled for the conversion; wherein the DMVD tool derives a refinement of motion information, and the coding mode comprises at least one of a merge mode with a motion vector difference that is indicated by a motion direction and a motion magnitude, or a motion vector prediction mode in which a motion vector is acquired based on a motion vector predictor; and   performing, based on the decision, the bitstream representation from the current block.