SBTMVP-BASED IMAGE OR VIDEO CODING
According to the disclosure of this document, in subblock-based temporal motion vector prediction (sbTMVP), a subblock position for deriving a motion vector in units of a subblock can be efficiently calculated, and through this, video/image coding efficiency can be improved and hardware implementation can be simplified.
1 . A method comprising:
obtaining residual information from a bitstream;
deriving a reference subblock on a collocated reference picture for a current subblock within a current block;
deriving a motion vector of the reference subblock;
deriving a subblock temporal motion vector predictor (sbTMVP) candidate based on the motion vector of the reference subblock;
generating prediction samples based on a motion vector of the current subblock derived based on the sbTMVP candidate;
deriving quantized transform coefficients for the current block based on the residual information;
deriving transform coefficients for the current block by performing a dequantization to the quantized transform coefficients;
generating residual samples for the current block by performing an inverse transform to the transform coefficients; and
generating a reconstructed picture based on the prediction samples and the residual samples;
wherein the reference subblock on the collocated reference picture is derived based on a position of a center lower-right sample among four samples positioned at a center of the current subblock,
wherein for the reference subblock that is not available, the motion vector of the reference subblock is set as a base motion vector, and
wherein the base motion vector is derived on the collocated reference picture based on a position of a center lower-right sample among four samples located at a center of the current block.
2 . A method comprising:
deriving a reference subblock on a collocated reference picture for a current subblock within a current block;
deriving a motion vector of the reference subblock;
deriving a subblock temporal motion vector predictor (sbTMVP) candidate based on the motion vector of the reference subblock;
generating prediction samples based on a motion vector of the current subblock derived based on the sbTMVP candidate;
generating residual samples based on the prediction samples;
deriving transform coefficients for the current block by performing a transform to the residual samples;
deriving quantized transform coefficients for the current block by performing a quantization based on the transform coefficients;
generating residual information based on the quantized transform coefficients; and
encoding image information including the residual information,
wherein the reference subblock on the collocated reference picture is derived based on a position of a center lower-right sample among four samples positioned at a center of the current subblock,
wherein for the reference subblock that is not available, the motion vector of the reference subblock is set as a base motion vector, and
wherein the base motion vector is derived on the collocated reference picture based on a position of a center lower-right sample among four samples located at a center of the current block.
3 . A method comprising:
obtaining a bitstream for the image, wherein the bitstream is generated based on deriving a reference subblock on a collocated reference picture for a current subblock within a current block, deriving a motion vector of the reference subblock, deriving a subblock temporal motion vector predictor (sbTMVP) candidate based on the motion vector of the reference subblock, generating prediction samples based on a motion vector of the current subblock derived based on the sbTMVP candidate, generating residual samples based on the prediction samples, deriving transform coefficients for the current block by performing a transform to the residual samples; deriving quantized transform coefficients for the current block by performing a quantization based on the transform coefficients; generating residual information based on the quantized transform coefficients; and encoding image information including the residual information; and
transmitting the data comprising the bitstream,
wherein the reference subblock on the collocated reference picture is derived based on a position of a center lower-right sample among four samples positioned at a center of the current subblock,
wherein for the reference subblock that is not available, the motion vector of the reference subblock is set as a base motion vector, and
wherein the base motion vector is derived on the collocated reference picture based on a position of a center lower-right sample among four samples located at a center of the current block.