US Patent 11936852 Sample identification for intra block copy in video coding

A method of video processing includes maintaining, for a conversion between a current video block of a current picture of a visual media data and a bitstream representation of the visual media data, a buffer comprising reference samples from the current picture for a derivation of prediction samples of the current video block. One or more reference samples in the buffer that are marked unavailable for the derivation have values outside of a pixel value range.