Video encoding method and device, and video decoding method and device
The present disclosure relates to apparatus and methods of image decoding and image encoding. In one or more embodiments, an image decoding method may comprise determining a first sample value of an upper left reference sample of the current block. The image decoding method may further comprise sequentially searching for a searched reference sample of at least one reference line from a plurality of reference lines, except for the upper left reference sample. The image decoding method may further comprise determining a second sample value of remaining reference samples of the current block, except for the upper left reference sample. The image decoding method may further comprise performing intra prediction on the current block to obtain a prediction block of the current block. The image decoding method may further comprise obtaining a residual block of the current block and a reconstruction block of the current block.
1 . An image decoding method, comprising:
determining, when a current prediction mode of a current block is an intra mode, a first sample value of an upper left reference sample of the current block by identifying a first availability of the upper left reference sample of the current block;
sequentially searching, for remaining reference samples of at least one reference line from a plurality of reference lines adjacent to the current block, except for the upper left reference sample, the plurality of reference lines comprising a left reference line of the current block, an upper reference line of the current block, and a right reference line of the current block;
determining second sample values of the remaining reference samples of the current block by identifying a second availability of the searched remaining reference samples;
performing intra prediction on the current block to obtain a prediction block of the current block, based on the first sample value of the upper left reference sample of the current block and the second sample values of the remaining reference samples of the current block; and
obtaining a reconstruction block of the current block, based on the prediction block of the current block,
wherein the determining of the first sample value of the upper left reference sample of the current block comprises:
determining, when the upper left reference sample is not available, a first value obtained based on a sample bit depth as the first sample value of the upper left reference sample without searching for available reference samples neighboring the upper left reference sample,
wherein the determining of the second sample values of the remaining reference samples of the current block comprises:
determining, when a current reference sample in a current search location is not available, a second value obtained based on a sample value of a reference sample in a previous search location as a current sample value of the current reference sample in the current search location,
wherein a first search direction of the upper reference line is a right direction relative to the upper left reference sample,
wherein a second search direction of the left reference line is a first lower direction relative to the upper left reference sample,
wherein a third search direction of the right reference line is a second lower direction relative to an upper right reference sample of the current block,
wherein when a coordinate value of an upper left corner sample of the current block is (0,0), a x-axis coordinate value of the upper right reference sample of the current block is a width of the current block, and a y-axis coordinate value of the upper right reference sample of the current block is −1,
wherein the first value is a median value between a minimum sample value and a maximum sample value indicated by the sample bit depth, and
wherein the image decoding method further comprises determining, when the intra prediction on the current block is performed by using only a reference sample reconstructed in the intra mode and a prediction mode of a reference block including the current reference sample corresponds to an inter mode, that the current reference sample is not available.
2 . An image decoding apparatus, comprising:
a memory; and
at least one processor communicatively coupled to the memory and configured to:
determine, when a current prediction mode of a current block is an intra mode, a first sample value of an upper left reference sample of the current block by identifying a first availability of the upper left reference sample of the current block;
sequentially search for remaining reference samples of at least one reference line from a plurality of reference lines adjacent to the current block, except for the upper left reference sample, the plurality of reference lines comprising a left reference line of the current block, an upper reference line of the current block, and a right reference line of the current block;
determine second sample values of the remaining reference samples of the current block by identifying a second availability of the searched remaining reference samples;
perform intra prediction on the current block to obtain a prediction block of the current block, based on the first sample value of the upper left reference sample of the current block and the second sample values of the remaining reference samples of the current block; and
obtain a reconstruction block of the current block, based on the prediction block of the current block,
wherein the at least one processor is further configured, when the at least one processor determines the first sample value of the upper left reference sample of the current block, to:
determine, when the upper left reference sample is not available, a first value obtained based on a sample bit depth as the first sample value of the upper left reference sample without searching for available reference samples neighboring the upper left reference sample,
wherein the at least one processor is further configured, when the at least one processor determines the second sample values of the remaining reference samples of the current block, to:
determine, when a current reference sample in a current search location is not available, a second value obtained based on a sample value of a reference sample in a previous search location as a current sample value of the current reference sample in the current search location,
wherein a first search direction of the upper reference line is a right direction relative to the upper left reference sample,
wherein a second search direction of the left reference line is a first lower direction relative to the upper left reference sample,
wherein a third search direction of the right reference line is a second lower direction relative to an upper right reference sample of the current block,
wherein when a coordinate value of an upper left corner sample of the current block is (0,0), a x-axis coordinate value of the upper right reference sample of the current block is a width of the current block, and a y-axis coordinate value of the upper right reference sample of the current block is −1,
wherein the first value is a median value between a minimum sample value and a maximum sample value indicated by the sample bit depth, and
wherein the at least one processor is further configured to determine, when the intra prediction on the current block is performed by using only a reference sample reconstructed in the intra mode and a prediction mode of a reference block including the current reference sample corresponds to an inter mode, that the current reference sample is not available.
3 . An image encoding method, comprising:
determining, when a prediction mode of a current block is an intra mode, a first sample value of an upper left reference sample of the current block by identifying a first availability of the upper left reference sample of the current block;
sequentially searching for remaining reference samples of at least one reference line from a plurality of reference lines adjacent to the current block, except for the upper left reference sample, the plurality of reference lines comprising a left reference line of the current block, an upper reference line of the current block, and a right reference line of the current block;
determining second sample values of the remaining reference samples of the current block by identifying a second availability of the searched remaining reference samples;
performing intra prediction on the current block to obtain a prediction block of the current block, based on the first sample value of the upper left reference sample of the current block and the second sample values of the remaining reference samples; and
generating a bitstream based on the prediction block of the current block,
wherein the determining of the first sample value of the upper left reference sample of the current block comprises:
determining, when the upper left reference sample is not available, a first value obtained based on a sample bit depth as the first sample value of the upper left reference sample without searching for available reference samples neighboring the upper left reference sample,
wherein the determining of the second sample values of the remaining reference samples of the current block comprises:
determining, when a current reference sample in a current search location is not available, a second value obtained based on a sample value of a reference sample in a previous search location as a current sample value of the current reference sample in the current search location,
wherein a first search direction of the upper reference line is a right direction relative to the upper left reference sample,
wherein a second search direction of the left reference line is a first lower direction relative to the upper left reference sample,
wherein a third search direction of the right reference line is a second lower direction relative to an upper right reference sample of the current block,
wherein when a coordinate value of an upper left corner sample of the current block is (0,0), a x-axis coordinate value of the upper right reference sample of the current block is a width of the current block, and a y-axis coordinate value of the upper right reference sample of the current block is −1,
wherein the first value is a median value between a minimum sample value and a maximum sample value indicated by the sample bit depth, and
wherein the image encoding method further comprises determining, when the intra prediction on the current block is performed by using only a reference sample reconstructed in the intra mode and a prediction mode of a reference block including the current reference sample corresponds to an inter mode, that the current reference sample is not available.
4 . A non-transitory computer-readable storage medium for storing a bitstream generated by an image encoding method, the image encoding method comprising:
determining, when a prediction mode of a current block is an intra mode, a first sample value of an upper left reference sample of the current block by identifying a first availability of the upper left reference sample of the current block;
sequentially searching for remaining reference samples of at least one reference line from a plurality of reference lines adjacent to the current block, except for the upper left reference sample, the plurality of reference lines comprising a left reference line of the current block, an upper reference line of the current block, and a right reference line of the current block;
determining second sample values of the remaining reference samples of the current block by identifying a second availability of the searched remaining reference samples;
performing intra prediction on the current block to obtain a prediction block of the current block, based on the first sample value of the upper left reference sample of the current block and the second sample values of the remaining reference samples; and
generating the bitstream based on the prediction block of the current block,
wherein the determining of the first sample value of the upper left reference sample of the current block comprises:
determining, when the upper left reference sample is not available, a first value obtained based on a sample bit depth as the first sample value of the upper left reference sample without searching for available reference samples neighboring the upper left reference sample,
wherein the determining of the second sample values of the remaining reference samples of the current block comprises:
determining, when a current reference sample in a current search location is not available, a second value obtained based on a sample value of a reference sample in a previous search location as a current sample value of the current reference sample in the current search location,
wherein a first search direction of the upper reference line is a right direction relative to the upper left reference sample,
wherein a second search direction of the left reference line is a first lower direction relative to the upper left reference sample,
wherein a third search direction of the right reference line is a second lower direction relative to an upper right reference sample of the current block,
wherein when a coordinate value of an upper left corner sample of the current block is (0,0), a x-axis coordinate value of the upper right reference sample of the current block is a width of the current block, and a y-axis coordinate value of the upper right reference sample of the current block is −1,
wherein the first value is a median value between a minimum sample value and a maximum sample value indicated by the sample bit depth, and
wherein the image encoding method further comprises determining, when the intra prediction on the current block is performed by using only a reference sample reconstructed in the intra mode and a prediction mode of a reference block including the current reference sample corresponds to an inter mode, that the current reference sample is not available.