Range constrains for block vector in intra-block copy mode

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:

• determine, for a conversion between a current video block of a video picture and a bitstream of the video picture, a prediction mode being applied to the current video block,
• determine, a block vector of the current video block based on the prediction mode,
• maintain, a virtual buffer comprising reference samples derived from blocks of sample values of the video picture;
• derive, in the prediction mode, prediction samples of the current video block based on the block vector and the virtual buffer, and
• perform the conversion based on the prediction samples,
• wherein a range constrain is applied to the block vector.

A non-transitory computer-readable storage medium storing instructions that cause a processor to:

• determine, for a conversion between a current video block of a video picture and a bitstream of the video picture, a prediction mode being applied to the current video block,
• determine, a block vector of the current video block based on the prediction mode,
• maintain, a virtual buffer comprising reference samples derived from blocks of sample values of the video picture;
• derive, in the prediction mode, prediction samples of the current video block based on the block vector and the virtual buffer, and
• perform the conversion based on the prediction samples,
• wherein a range constrain is applied to the block vector.

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:

• determining, for a current video block of a video picture, a prediction mode being applied to the current video block,
• determining, a block vector of the current video block based on the prediction mode,
• maintaining, a virtual buffer comprising reference samples derived from blocks of sample values of the video picture;
• deriving, in the prediction mode, prediction samples of the current video block based on the block vector and the virtual buffer, and
• generating the bitstream based on the determining,
• wherein a range constrain is applied to the block vector.