Video encoding method and device involving intra prediction, and video decoding method and device

A video decoding apparatus comprising:

• a candidate intra prediction mode determiner configured to
• determine reference intra prediction modes, based on availability and prediction modes of adjacent blocks of a current block, and
• determine candidate intra prediction modes for the current block, based on the reference intra prediction mode;
• and
• an intra predictor configured to
• obtain, from a bitstream, candidate intra prediction flag indicating whether one of the candidate intra prediction modes is selected as an intra prediction mode of the current block, when the candidate intra prediction flag indicates that one of the candidate intra prediction modes is selected as the intra prediction mode of the current block, obtaining, from the bitstream, current intra prediction information indicating the intra prediction mode of the current block from among the candidate intra prediction modes,
• select the intra prediction mode of the current block, from among the candidate intra prediction modes according to the current intra prediction information, and
• perform intra prediction on the current block, according to the intra prediction mode of the current block,
• wherein,
• the determining the reference intra prediction modes includes:
• determining a first intra prediction mode of the current block based on a left adjacent block of the current block;
• and
• determining a second intra prediction mode of the current block based on an upper adjacent block of the current block, and
• the determining the candidate intra prediction modes includes:
• determining a bilinear mode and a DC mode as the candidate intra prediction modes, where the first intra prediction mode and the second intra prediction mode are identical and the first intra prediction mode is the DC mode,
• determining the first intra prediction mode and the DC mode as the candidate intra prediction modes, where the first intra prediction mode and the second intra prediction mode are identical and the first intra prediction mode is not the DC mode.

A video encoding method comprising:

• determining reference intra prediction modes, based on availability and prediction modes of adjacent blocks of a current block;
• determining candidate intra prediction modes for the current block, based on the reference intra prediction mode;
• and
• based on an intra prediction mode of the current block and the plurality of candidate intra prediction modes of the current block, determining candidate intra prediction flag indicating whether the current block is predicted according to one of the candidate intra prediction modes, and current intra prediction information indicating the intra prediction mode of the current block from among the candidate intra prediction modes;
• and
• outputting a bitstream including the candidate intra prediction flag and the current intra prediction information,
• wherein,
• the determining the reference intra prediction modes includes:
• determining a first intra prediction mode of the current block based on a left adjacent block of the current block;
• and
• determining a second intra prediction mode of the current block based on an upper adjacent block of the current block, and
• the determining the candidate intra prediction modes includes:
• determining a bilinear mode and a DC mode as the candidate intra prediction modes, where the first intra prediction mode and the second intra prediction mode are identical and the first intra prediction mode is the DC mode,
• determining the first intra prediction mode and the DC mode as the candidate intra prediction modes, where the first intra prediction mode and the second intra prediction mode are identical and the first intra prediction mode is not the DC mode.