Block vector difference signaling based on validity determination

An apparatus comprising:

• one or more processors;
• and
• memory storing instructions that, when executed by the one or more processors, cause the apparatus to:
• receive, in a bitstream for a block, an indication of a block vector predictor (BVP) and a first and a second component magnitude of a block vector difference (BVD);
• determine each of a plurality of block vector (BV) candidates based on a sum of the BVP and a different one of a plurality of BVD candidates, wherein each of the plurality of BVD candidates comprises:
• the first and second component magnitudes of the BVD;
• and
• a different combination of signs for the first and second component magnitudes;
• and
• determine validities of the plurality of BV candidates based on values of samples, stored in a reference memory, of reference blocks indicated by the plurality of BV candidates;
• and
• determine a sign for at least one of the first and second component magnitudes of the BVD based on the validities of the plurality of BV candidates.

A non-transitory computer-readable medium storing instructions that, when executed by one or more processors of an apparatus, cause the apparatus to:

• receive, in a bitstream for a block, an indication of a block vector predictor (BVP) and a first and a second component magnitude of a block vector difference (BVD);
• determine each of a plurality of block vector (BV) candidates based on a sum of the BVP and a different one of a plurality of BVD candidates, wherein each of the plurality of BVD candidates comprises:
• the first and second component magnitudes of the BVD;
• and
• a different combination of signs for the first and second component magnitudes;
• and
• determine validities of the plurality of BV candidates based on values of samples, stored in a reference memory, of reference blocks indicated by the plurality of BV candidates;
• and
• determine a sign for at least one of the first and second component magnitudes of the BVD based on the validities of the plurality of BV candidates.