Method of determining transform coefficient scan order based on high frequency zeroing and apparatus thereof
An image decoding method performed by a decoding apparatus according to the present disclosure includes receiving a bitstream including residual information; deriving quantized transform coefficients for a current block based on the residual information included in the bitstream; deriving transform coefficients for the current block from the quantized transform coefficients based on an inverse quantization process; deriving residual samples for the current block by applying inverse transform to the derived transform coefficients; and generating a reconstructed picture based on the residual samples for the current block.
1. An image decoding method performed by a decoding apparatus, the method comprising:
receiving a bitstream including residual information;
obtaining last significant coefficient related information based on the residual information;
deriving transform coefficients for a current block based on the last significant coefficient related information;
deriving residual samples for the current block from the transform coefficients based on an inverse transform; and
generating a reconstructed picture based on the residual samples for the current block,
wherein the current block includes a first region and a second region,
wherein the first region is a region related to a last significant coefficient, and the second region is a region different from the first region in the current block,
wherein the last significant coefficient related information includes:
a last_sig_coeff_x_prefix syntax element related to an x component of a position of the last significant coefficient of the current block,
a last_sig_coeff_y_prefix syntax element related to an y component of a position of the last significant coefficient of the current block,
wherein the last_sig_coeff_x_prefix syntax element is based on truncated rice binarization,
wherein the last_sig_coeff_y_prefix syntax element is based on truncated rice binarization,
wherein based on both a transform block width and a transform block height of the current block being equal to 64,
a width of the first region is determined as 32,
a height of the first region is determined as 32,
a maximum length of a codeword for the last_sig_coeff_x_prefix syntax element is determined as 9 for the transform block width of the current block being equal to 64 based on a determination that the width of the first region is 32,
a maximum length of a codeword for the last_sig_coeff_y_prefix syntax element is determined as 9 for the transform block height of the current block being equal to 64 based on a determination that the height of the first region is 32,
wherein transform coefficient subblock scanning is performed for the current block based on diagonal direction within the first region, and
wherein with regard to the current block, coded subblock flags for subblocks located outside of the first region are not included in the residual information.
2. An image encoding method by an encoding apparatus, the method comprising:
deriving residual samples for a current block;
deriving transform coefficients for the current block based on the residual samples for the current block;
generating last significant coefficient related information based on the transform region related information;
encoding residual information related with the transform coefficients based on the transform coefficients,
wherein the current block includes a first region and a second region,
wherein the first region is a region related to a last significant coefficient, and the second region is a region different from the first region in the current block,
wherein the last significant coefficient related information includes:
a last_sig_coeff_x_prefix syntax element related to an x component of a position of the last significant coefficient of the current block,
a last_sig_coeff_y_prefix syntax element related to an y component of a position of the last significant coefficient of the current block,
wherein the last_sig_coeff_x_prefix syntax element is based on truncated rice binarization,
wherein the last_sig_coeff_y_prefix syntax element is based on truncated rice binarization,
wherein based on both a transform block width and a transform block height of the current block being equal to 64,
a width of the first region is determined as 32,
a height of the first region is determined as 32,
a maximum length of a codeword for the last_sig_coeff_x_prefix syntax element is determined as 9 for the transform block width of the current block being equal to 64 based on a determination that the width of the first region is 32,
a maximum length of a codeword for the last_sig_coeff_y_prefix syntax element is determined as 9 for the transform block height of the current block being equal to 64 based on a determination that the height of the first region is 32,
wherein transform coefficient subblock scanning is performed for the current block based on diagonal direction within the first region, and
wherein with regard to the current block, coded subblock flags for subblocks located outside of the first region are not included in the residual information.
3. A transmission method for transmitting data including a bitstream of image information, the transmission method comprising:
obtaining a bitstream of the image information including residual information, wherein the bitstream is generated based on deriving residual samples for a current block, deriving transform coefficients for the current block based on the residual samples for the current block, generating last significant coefficient related information based on the transform coefficients, and encoding residual information related to the transform coefficients based on the last significant coefficient related information; and
transmitting the data including the bitstream,
wherein the current block includes a first region and a second region,
wherein the first region is a region related to a last significant coefficient, and the second region is a region different from the first region in the current block,
wherein the last significant coefficient related information includes:
a last_sig_coeff_x_prefix syntax element related to an x component of a position of the last significant coefficient of the current block,
a last_sig_coeff_y_prefix syntax element related to an y component of a position of the last significant coefficient of the current block,
wherein the last_sig_coeff_x_prefix syntax element is based on truncated rice binarization,
wherein the last_sig_coeff_y_prefix syntax element is based on truncated rice binarization,
wherein based on both a transform block width and a transform block height of the current block being equal to 64,
a width of the first region is determined as 32,
a height of the first region is determined as 32,
a maximum length of a codeword for the last_sig_coeff_x_prefix syntax element is determined as 9 for the transform block width of the current block being equal to 64 based on a determination that the width of the first region is 32,
a maximum length of a codeword for the last_sig_coeff_y_prefix syntax element is determined as 9 for the transform block height of the current block being equal to 64 based on a determination that the height of the first region is 32,
wherein transform coefficient subblock scanning is performed for the current block based on diagonal direction within the first region, and
wherein with regard to the current block, coded subblock flags for subblocks located outside of the first region are not included in the residual information.