Restriction of applicability for 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 and a bitstream of the video, whether a first prediction mode is enabled based on a rule;
• and
• perform the conversion based on the determination;
• wherein in the first prediction mode, prediction samples are derived from blocks of sample values of a same decoded slice as determined by block vectors, and wherein the rule specifies that the first prediction mode is not enabled in response to a width of the current video block being greater than a first predetermined value or a height of the current video block being greater than a second predetermined value,
• wherein the rule further specifies that the first prediction mode is not enabled in response to the current video block being a first block in a coding tree block row including the current video block, and
• wherein the instructions further cause the processor to:
• construct a first motion candidate list for the first prediction mode, wherein a maximum number of motion candidates in the first motion candidate list is equal to M1, M1 being equal to or greater than 1;
• and
• construct, for a second conversion between a second video block of the video and the bitstream, a second motion candidate list in an inter merge prediction mode, wherein a maximum number of motion candidates in the second motion candidate list is equal to M2, M2 being equal to or greater than 1,
• wherein at most L1 candidates in a first history-based motion vector predictor (HMVP) candidate table are inserted into the first motion candidate list, and wherein candidates in the first HMVP candidate table are arranged based on a sequence of an addition of the candidates into the first HMVP candidate table, L1 being equal to or greater than 0,
• wherein at most L2 candidates in a second HMVP candidate table are inserted into the second motion candidate list, and wherein candidates in the second HMVP candidate table are arranged based on a sequence of an addition of the candidates into the second HMVP candidate table, L2 being equal to or greater than 0, and
• wherein in a case that M1 is equal to M2, L1 is not equal to L2.

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 and a bitstream of the video, whether a first prediction mode is enabled based on a rule;
• and
• perform the conversion based on the determination;
• wherein in the first prediction mode, prediction samples are derived from blocks of sample values of a same decoded slice as determined by block vectors, and wherein the rule specifies that the first prediction mode is not enabled in response to a width of the current video block being greater than a first predetermined value or a height of the current video block being greater than a second predetermined value,
• wherein the rule further specifies that the first prediction mode is not enabled in response to the current video block being a first block in a coding tree block row including the current video block, and
• wherein the instructions further cause the processor to:
• construct a first motion candidate list for the first prediction mode, wherein a maximum number of motion candidates in the first motion candidate list is equal to M1, M1 being equal to or greater than 1;
• and
• construct, for a second conversion between a second video block of the video and the bitstream, a second motion candidate list in an inter merge prediction mode, wherein a maximum number of motion candidates in the second motion candidate list is equal to M2, M2 being equal to or greater than 1,
• wherein at most L1 candidates in a first history-based motion vector predictor (HMVP) candidate table are inserted into the first motion candidate list, and wherein candidates in the first HMVP candidate table are arranged based on a sequence of an addition of the candidates into the first HMVP candidate table, L1 being equal to or greater than 0,
• wherein at most L2 candidates in a second HMVP candidate table are inserted into the second motion candidate list, and wherein candidates in the second HMVP candidate table are arranged based on a sequence of an addition of the candidates into the second HMVP candidate table, L2 being equal to or greater than 0, and
• wherein in a case that M1 is equal to M2, L1 is not equal to L2.

A method for storing a bitstream of a video, comprising:

• determining, for a current video block of the video, that whether a first prediction mode is enabled based on a rule;
• and
• generating the bitstream based on the determining;
• and
• storing the bitstream in a non-transitory computer-readable recording medium;
• wherein in the first prediction mode, prediction samples are derived from blocks of sample values of a same decoded slice as determined by block vectors, and wherein the rule specifies that the first prediction mode is not enabled in response to a width of a current video block of the video being greater than a first predetermined value or a height of the current video block being greater than a second predetermined value,
• wherein the rule further specifies that the first prediction mode is not enabled in response to the current video block being a first block in a coding tree block row including the current video block, and
• wherein the method further comprises:
• constructing a first motion candidate list for the first prediction mode, where in a maximum number of motion candidates in the first motion candidate list is equal to M1, M1 being equal to or greater than 1;
• and
• constructing, for a second conversion between a second video block of the video and the bitstream, a second motion candidate list in an inter merge prediction mode, wherein a maximum number of motion candidates in the second motion candidate list is equal to M2, M2 being equal to or greater than 1,
• wherein at most L1 candidates in a first history-based motion vector predictor (HMVP) candidate table are inserted into the first motion candidate list, and wherein candidates in the first HMVP candidate table are arranged based on a sequence of an addition of the candidates into the first HMVP candidate table, L1 being equal to or greater than 0,
• wherein at most L2 candidates in a second HMVP candidate table are inserted into the second motion candidate list, and wherein candidates in the second HMVP candidate table are arranged based on a sequence of an addition of the candidates into the second HMVP candidate table, L2 being equal to or greater than 0, and
• wherein in a case that M1 is equal to M2, L1 is not equal to L2.