Method and apparatus of decoder side motion derivation for video coding

Abstract

Method and apparatus of video coding using decoder derived motion information based on bilateral matching or template matching are disclosed. According to one method, an initial motion vector (MV) index is signalled in a video bitstream at an encoder side or determined from the video bitstream at a decoder side. A selected MV is then derived using bilateral matching, template matching or both to refine an initial MV associated with the initial MV index. In another method, when both MVs for list 0 and list 1 exist in template matching, the smallest-cost MV between the two MVs may be used for uni-prediction template matching if the cost is lower than the bi-prediction template matching. According to yet another method, the refinement of the MV search is dependent on the block size. According to yet another method, merge candidate MV pair is always used for bilateral matching or template matching.

1 . A method of motion vector (MV) derivation, the method comprising:
 receiving input data associated with a current block in a current picture;   determining a first initial MV for a first reference picture list and a second initial MV for a second reference picture list;   obtaining a refined MV pair by determining a MV offset pair to refine the first initial MV and the second initial MV, comprising:   calculating a sum of absolute difference (SAD) cost of a first reference block associated with the first initial MV and the one MV of the MV offset pair and a second reference block associated with the second initial MV and the another MV of the MV offset pair, wherein one sample out of K×L samples in the first reference block and the second reference block is used for calculating the SAD cost, K and L are integers; and   encoding or decoding the current block or a current MV of the current block using the refined MV pair at the encoder side or the decoder side respectively.   
     
     
         2 . The method of  claim 1 , wherein K is equal to 2. 
     
     
         3 . The method of  claim 1 , wherein L is equal to 2. 
     
     
         4 . The method of  claim 1 , wherein an initial motion vector (MV) index associated with the first initial MV and the second initial MV is signaled in a video bitstream at an encoder side or determined from the video bitstream at a decoder side. 
     
     
         5 . The method of  claim 1 , wherein the step of obtaining the refined MV pair is performed only when a block size of the current block is greater than a first threshold. 
     
     
         6 . An apparatus of motion vector (MV) derivation, the apparatus comprising one or more electronic circuits or processors arranged to:
 receive input data associated with a current block in a current picture;   determine a first initial MV for a first reference picture list and a second initial MV for a second reference picture list;   obtain a refined MV pair by determining a MV offset pair to refine the first initial MV and the second initial MV, comprising:   calculate a sum of absolute difference (SAD) cost of a first reference block associated with the first initial MV and the one MV of the MV offset pair and a second reference block associated with the second initial MV and the another MV of the MV offset pair, wherein one sample out of K×L samples in the first reference block and the second reference block is used for calculating the SAD cost, K and L are integers; and   encode or decode the current block or a current MV of the current block using the refined MV pair at the encoder side or the decoder side respectively.   
     
     
         7 . The apparatus of  claim 6 , wherein K is equal to 2. 
     
     
         8 . The apparatus of  claim 6 , wherein L is equal to 2. 
     
     
         9 . The apparatus of  claim 6 , wherein an initial motion vector (MV) index associated with the first initial MV and the second initial MV is signaled in a video bitstream at an encoder side or determined from the video bitstream at a decoder side. 
     
     
         10 . The apparatus of  claim 6 , wherein the refined MV pair is obtained only when a block size of the current block is greater than a first threshold.