Buffer updating for intra block copy in video coding
A method of visual media processing includes determining a size of a buffer to store reference samples for prediction in an intra block copy mode; and performing a conversion between a current video block of visual media data and a bitstream of the current video block, using the reference samples stored in the buffer, wherein the conversion is performed in the intra block copy mode which is based on motion information related to a reconstructed block located in same video region with the current video block without referring to a reference picture.
1. A method of processing video data, comprising:
performing a conversion between a current video block and a bitstream of the current video block; and
updating a buffer which is used to store reference samples for prediction in an intra block copy mode, wherein the buffer is used for a conversion between a subsequent video block and a bitstream of the subsequent video block, wherein the conversion between the subsequent video block and a bitstream of the subsequent video block is performed in the intra block copy mode which is based on motion information related to a reconstructed block located in a same video region with the subsequent video block without referring to a reference picture;
wherein reconstructed samples of the current video block are modified before being stored in the buffer,
wherein a bit-depth conversion is performed on the reconstructed samples of the current video block before being stored in the buffer, and
wherein the bit-depth conversion corresponds to an alignment of a bit-depth of the reconstructed samples to a bit-depth of the buffer,
wherein a sample at a reference location within the buffer is updated with a reconstructed sample of the current video block according to an operation expressed as:
{ p+[ 1<<( b− 1)]}>> b , or
clip({ p+[ 1<<( b− 1)]}>> b, 0, (1<<bitdepth)−1), or
{ p+[ 1<<( b− 1)−1]}>> b , or
clip({ p+[ 1<<( b− 1)−1]}>> b, 0, (1<<bitdepth)−1), and
wherein p is the reconstructed sample, b is a bit-shifting value, “clip” is a clipping operation, and bitdepth is the bit-depth of the buffer.
2. The method of claim 1 , wherein the conversion between the current video block and the bitstream of the current video block is performed in the intra block copy mode.
3. The method of claim 1 , wherein the sample at the reference location (x mod M, y mod N) in the buffer is updated with the reconstructed sample located at position (x, y) relative to an upper-left corner of a video region associated with the current video block.
4. The method of claim 3 , wherein the video region is one of: a picture, a slice, a tile, or a coding tree unit.
5. The method of claim 1 , wherein the reference location within the buffer is derived based on a position of the reconstructed sample of the current video block and a position offset.
6. The method of claim 1 , wherein the reconstructed samples of the current video block correspond to pre-filtered samples.
7. The method of claim 1 , wherein the reconstructed samples of the current video block correspond to post-filtered samples.
8. The method of claim 1 , wherein the bit-depth conversion corresponds to a change in the bit-depth of the reconstructed samples.
9. The method of claim 1 , wherein the conversion includes encoding the current video block into the bitstream.
10. The method of claim 1 , wherein the conversion includes decoding the current video block from the bitstream.
11. An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
perform a conversion between a current video block and a bitstream of the current video block; and
update a buffer which is used to store reference samples for prediction in an intra block copy mode, wherein the buffer is used for a conversion between a subsequent video block and a bitstream of the subsequent video block, wherein the conversion between the subsequent video block and a bitstream of the subsequent video block is performed in the intra block copy mode which is based on motion information related to a reconstructed block located in same video region with the subsequent video block without referring to a reference picture;
wherein reconstructed samples of the current video block are modified before being stored in the buffer,
wherein a bit-depth conversion is performed on the reconstructed samples of the current video block before being stored in the buffer, and
wherein the bit-depth conversion corresponds to an alignment of a bit-depth of the reconstructed samples to a bit-depth of the buffer,
wherein a sample at a reference location within the buffer is updated with a reconstructed sample of the current video block according to an operation expressed as:
{ p+[ 1<<( b− 1)]}>> b , or
clip({ p+[ 1<<( b− 1)]}>> b, 0, (1<<bitdepth)−1), or
{ p+[ 1<<( b− 1)−1]}>> b , or
clip({ p+[ 1<<( b− 1)−1]}>> b, 0, (1<<bitdepth)−1), and
wherein p is the reconstructed sample, b is a bit-shifting value, “clip” is a clipping operation, and bitdepth is the bit-depth of the buffer.
12. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises:
generating the bitstream based on a current video block;
updating a buffer which is used to store reference samples for prediction in an intra block copy mode, wherein the buffer is used for a conversion between a subsequent video block and a bitstream of the subsequent video block, wherein the conversion between the subsequent video block and a bitstream of the subsequent video block is performed in the intra block copy mode which is based on motion information related to a reconstructed block located in same video region with the subsequent video block without referring to a reference picture;
wherein reconstructed samples of the current video block are modified before being stored in the buffer,
wherein a bit-depth conversion is performed on the reconstructed samples of the current video block before being stored in the buffer, and
wherein the bit-depth conversion corresponds to an alignment of a bit-depth of the reconstructed samples to a bit-depth of the buffer,
wherein a sample at a reference location within the buffer is updated with a reconstructed sample of the current video block according to an operation expressed as:
{ p+[ 1<<( b− 1)]}>> b , or
clip({ p+[ 1<<( b− 1)]}>> b, 0, (1<<bitdepth)−1), or
{ p+[ 1<<( b− 1)−1]}>> b , or
clip({ p+[ 1<<( b− 1)−1]}>> b, 0, (1<<bitdepth)−1), and
wherein p is the reconstructed sample, b is a bit-shifting value, “clip” is a clipping operation, and bitdepth is the bit-depth of the buffer.