Buffer updating for intra block copy in video coding

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.

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.