Method and apparatus for deriving an interpolation filter index for a current block

A decoder, comprising:

• one or more processors;
• and
• a non-transitory computer-readable storage medium coupled to the one or more processors and storing programming instructions, which when executed by the one or more processors, cause the decoder to perform operations for decoding a block in a frame of a video signal, the operations comprising:
• performing entropy decoding on a received bitstream to obtain quantized coefficients and syntax elements;
• applying inverse quantization on the quantized coefficients to obtain dequantized coefficients;
• applying inverse transform on the dequantized coefficients to obtain a reconstructed residual block;
• performing inter prediction for the block in the frame of the video signal to obtain a prediction block, comprising:
• constructing a history-based motion information candidate list, wherein the history-based motion information candidate list is an ordered list comprising N history-based motion information candidates Hk, k=0, . . . , N-1, containing motion information of N preceding blocks preceding the block, wherein N is an integer greater than 0, wherein each history-based motion information candidate comprises:
• i) one or more motion vectors (MVs),
• ii) one or more reference picture indices corresponding to the MVs, and
• iii) an interpolation filter (IF) index;
• adding one or more of the N history-based motion information candidates Hk from the history-based motion information candidate list into a motion information candidate list for the block;
• and
• deriving motion information of the block based on the motion information candidate list, wherein the motion information of the block is used for inter prediction for the block to obtain the prediction block;
• and
• adding the reconstructed residual block to the prediction block to obtain a reconstructed block of the block;
• wherein a history-based motion information candidate Hk, k=N, containing the motion information of the block is added to the history-based motion information candidate list when it is determined that at least one of the following elements of each history-based motion information candidate of the history-based motion information candidate list differs from a corresponding element of the motion information of the block:
• i) the one or more MVs, or
• ii) the one or more reference picture indices corresponding to the one or more MVs;
• wherein the determination of the at least one of the elements of each history-based motion information candidate of the history-based motion information candidate list differs from the corresponding element of the motion information of the block comprises:
• comparing whether the one or more MVs of a history-based motion information candidate in the history-based motion information candidate list are same as corresponding one or more MVs of the block;
• and
• comparing whether the one or more reference picture indices of the history-based motion information candidate are same as corresponding one or more reference picture indices of the block, wherein the comparison is performed on checking differences with respect to the one or more MVs and the one or more reference picture indices, without comparison of the IF index.

A non-transitory computer-readable medium storing a program code, which when executed by a computer device, causes the computer device to perform operations for decoding a block in a frame of a video signal, the operations comprising:

• performing entropy decoding on a received bitstream to obtain quantized coefficients and syntax elements;
• applying inverse quantization on the quantized coefficients to obtain dequantized coefficients;
• applying inverse transform on the dequantized coefficients to obtain a reconstructed residual block;
• performing inter prediction for the block in the frame of the video signal to obtain a prediction block, comprising:
• constructing a history-based motion information candidate list, wherein the history-based motion information candidate list is an ordered list comprising N history-based motion information candidates Hk, k=0, . . . , N-1, containing motion information of N preceding blocks preceding the block, wherein N is an integer greater than 0, wherein each history-based motion information candidate comprises:
• i) one or more motion vectors (MVs),
• ii) one or more reference picture indices corresponding to the MVs, and
• iii) an interpolation filter (IF) index;
• adding one or more of the N history-based motion information candidates Hk from the history-based motion information candidate list into a motion information candidate list for the block;
• and
• deriving motion information of the block based on the motion information candidate list, wherein the motion information of the block is used for inter prediction for the block to obtain the prediction block;
• and
• adding the reconstructed residual block to the prediction block to obtain a reconstructed block of the block;
• wherein a history-based motion information candidate Hk, k=N, containing the motion information of the block is added to the history-based motion information candidate list when it is determined that at least one of the following elements of each history-based motion information candidate of the history-based motion information candidate list differs from a corresponding element of the motion information of the block:
• i) the one or more MVs, or
• ii) the one or more reference picture indices corresponding to the one or more MVs;
• wherein the determination of the at least one of the elements of each history-based motion information candidate of the history-based motion information candidate list differs from the corresponding element of the motion information of the block comprises:
• comparing whether the one or more MVs of a history-based motion information candidate in the history-based motion information candidate list are same as corresponding one or more MVs of the block;
• and
• comparing whether the one or more reference picture indices of the history-based motion information candidate are same as corresponding one or more reference picture indices of the block, wherein the comparison is performed on checking differences with respect to the one or more MVs and the one or more reference picture indices, without comparison of the IF index.