Video encoding apparatus, video decoding apparatus, and video decoding method for performing intra-prediction based on directionality of neighboring block

A video encoding method performed by a video encoding apparatus, the method comprising:

• determining a current intra prediction mode associated with a current block;
• performing intra-prediction according to the current intra prediction mode associated with the current block to generate a prediction block associated with the current block;
• determining a neighboring intra prediction mode associated with a neighboring block, the neighboring block being adjacent to the current block;
• encoding the current intra prediction mode associated with the current block based on whether the neighboring intra prediction mode associated with the neighboring block has directionality or not;
• obtaining a residual block associated with the current block by using the prediction block and the current block;
• transforming the residual block to generate transform coefficients;
• quantizing the transform coefficients to generate quantized transform coefficients;
• encoding the quantized transform coefficients, wherein the encoding the current intra prediction mode associated with the current block comprises:
• determining candidate intra prediction modes associated with the current block according to a first set of two or more mathematical expressions, when the neighboring intra prediction mode associated with the neighboring block has no directionality,
• determining candidate intra prediction modes associated with the current block according to a second set of two or more mathematical expressions, when the neighboring intra prediction mode associated with the neighboring block has directionality,
• encoding the current intra prediction mode associated with the current block based on the candidate intra prediction modes,
• wherein the second set of two or more mathematical expressions is different from the first set of two or more mathematical expressions,
• wherein the second set of two or more mathematical expressions use the neighboring intra prediction mode associated with the neighboring block, and
• the neighboring block includes an upper block adjacent to the current block.

A method of transmitting a bitstream performed by an image encoding apparatus, the method comprising:

• determining a current intra prediction mode associated with a current block;
• performing intra-prediction according to the current intra prediction mode associated with the current block to generate a prediction block associated with the current block;
• determining a neighboring intra prediction mode associated with a neighboring block, the neighboring block being adjacent to the current block;
• encoding, into the bitstream, the current intra prediction mode associated with the current block based on whether the neighboring intra prediction mode associated with the neighboring block has directionality or not;
• obtaining a residual block associated with the current block by using the prediction block and the current block;
• transforming the residual block to generate transform coefficients;
• quantizing the transform coefficients to generate quantized transform coefficients;
• and
• encoding, into the bitstream, the quantized transform coefficients;
• and
• transmitting the bitstream to an image decoding apparatus,
• wherein the encoding the current intra prediction mode associated with the current block comprises:
• determining candidate intra prediction modes associated with the current block according to a first set of two or more mathematical expressions, when the neighboring intra prediction mode associated with the neighboring block has no directionality,
• determining candidate intra prediction modes associated with the current block according to a second set of two or more mathematical expressions, when the neighboring intra prediction mode associated with the neighboring block has directionality,
• encoding the current intra prediction mode associated with the current block based on the candidate intra prediction modes,
• wherein the second set of two or more mathematical expressions is different from the first set of two or more mathematical expressions,
• wherein the second set of two or more mathematical expressions use the neighboring intra prediction mode associated with the neighboring block, and
• the neighboring block includes an upper block adjacent to the current block.