Method for encoding/decoding image signal and device for same

A video encoding method comprising:

• determining a reference sample line of a current block;
• deriving an intra prediction mode of the current block based on whether the intra prediction mode of the current block is a same intra prediction mode as a candidate intra prediction mode;
• performing intra prediction on the current block based on the reference sample line and the derived intra prediction mode;
• determining transform type candidates, wherein the transform type candidates vary according to whether an explicit determination manner of transform type is allowed, whether the explicit determination manner is allowed is indicated through flag information in a bitstream, and a first number of transform type candidates when the explicit determination manner is allowed is greater than a second number of transform type candidates when the explicit determination manner is not allowed, the first number and the second number are both positive integers;
• and
• determining whether or not to partition the current block into a plurality of subblocks, wherein
• when the current block is partitioned into a plurality of subblocks, the plurality of subblocks share one intra prediction mode;
• and
• when the explicit determination manner is not allowed, a horizontal direction transform type of a subblock is determined based on a width of the subblock, and a vertical direction transform type of the subblock is determined based on a height of the subblock;
• wherein when a difference between an intra prediction mode of a top neighboring block and an intra prediction mode of a left neighboring block is 64, at least one among the candidate intra prediction modes is derived by adding or subtracting 2 to or from a maximum value.

A decoder, comprising:

• a memory, for storing instructions executable by a processor,
• the processor, for performing the instructions to execute operations of:
• determining a reference sample line of a current block;
• deriving an intra prediction mode of the current block based on whether the intra prediction mode of the current block is a same intra prediction mode as a candidate intra prediction mode;
• performing intra prediction on the current block based on the reference sample line and the derived intra prediction mode;
• determining transform type candidates, wherein the transform type candidates vary according to whether an explicit determination manner of transform type is allowed, whether the explicit determination manner is allowed is indicated through flag information in a bitstream, and a first number of transform type candidates when the explicit determination manner is allowed is greater than a second number of transform type candidates when the explicit determination manner is not allowed, the first number and the second number are both positive integers;
• and
• determining whether or not to partition the current block into a plurality of subblocks, wherein
• when the current block is partitioned into a plurality of subblocks, the plurality of subblocks share one intra prediction mode;
• and
• when the explicit determination manner is not allowed, a horizontal direction transform type of a subblock is determined based on a width of the subblock, and a vertical direction transform type of the subblock is determined based on a height of the subblock;
• wherein when a difference between an intra prediction mode of a top neighboring block and an intra prediction mode of a left neighboring block is 64, at least one among the candidate intra prediction modes is derived by adding or subtracting 2 to or from a maximum value.

An encoder, comprising:

• a memory, for storing instructions executable by a processor,
• the processor, for performing the instructions to execute operations of:
• determining a reference sample line of a current block;
• deriving an intra prediction mode of the current block based on whether the intra prediction mode of the current block is a same intra prediction mode as a candidate intra prediction mode;
• performing intra prediction on the current block based on the reference sample line and the derived intra prediction mode;
• determining transform type candidates, wherein the transform type candidates vary according to whether an explicit determination manner of transform type is allowed, whether the explicit determination manner is allowed is indicated through flag information in a bitstream, and a first number of transform type candidates when the explicit determination manner is allowed is greater than a second number of transform type candidates when the explicit determination manner is not allowed, the first number and the second number are both positive integers;
• and
• determining whether or not to partition the current block into a plurality of subblocks, wherein
• when the current block is partitioned into a plurality of subblocks, the plurality of subblocks share one intra prediction mode;
• and
• when the explicit determination manner is not allowed, a horizontal direction transform type of a subblock is determined based on a width of the subblock, and a vertical direction transform type of the subblock is determined based on a height of the subblock;
• wherein when a difference between an intra prediction mode of a top neighboring block and an intra prediction mode of a left neighboring block is 64, at least one among the candidate intra prediction modes is derived by adding or subtracting 2 to or from a maximum value.