Method for encoding/decoding an intra-picture prediction mode using two intra-prediction mode candidate, and apparatus using such a method

A method of encoding a video signal, comprising:

• determining an intra-prediction mode of a current block;
• generating, a prediction sample relating to the current block included in the video signal to be encoded by performing intra prediction;
• deriving a first candidate intra-prediction mode and a second candidate intra-prediction mode of a current block;
• and
• encoding n-bit information specifying whether the intra-prediction mode of the current block is identical to the first candidate intra-prediction mode or the second candidate intra-prediction mode;
• when the intra-prediction mode of the current block is identical to one of the first candidate intra-prediction mode and the second candidate intra-prediction mode, encoding m-bit information specifying one of the first candidate intra-prediction mode and the second candidate intra-prediction mode identical to the intra-prediction mode of the current block;
• wherein deriving the first candidate intra-prediction mode and the second candidate intra-prediction mode comprises:
• deriving a first neighbor prediction mode based on a first neighbor block adjacent to the current block,
• wherein when the first neighbor block is available, the first neighbor prediction mode is set to as an intra-prediction mode of the first neighbor block, and
• wherein when the first neighbor block is unavailable, the first neighbor prediction mode is set to a DC mode;
• deriving a second neighbor prediction mode based on a second neighbor block adjacent to the current block,
• wherein when the second neighbor block is available, the second neighbor prediction mode is set to as an intra-prediction mode of the second neighbor block, and
• wherein when the second neighbor block is unavailable, the second neighbor prediction mode is set to a DC mode;
• and
• deriving the first candidate intra-prediction mode and the second candidate intra-prediction mode from the first neighbor prediction mode and the second neighbor prediction mode,
• wherein when the first neighbor prediction mode and the second neighbor prediction mode are different, the first candidate intra-prediction mode and the second candidate intra-prediction mode are determined without comparing values of the first neighbor prediction mode and the second neighbor prediction mode.

A non-transitory computer-readable recording medium storing a bitstream that is generated by a method of encoding a video signal, wherein the method comprises

• determining an intra-prediction mode of a current block;
• generating, a prediction sample relating to the current block included in the video signal to be encoded by performing intra prediction;
• deriving a first candidate intra-prediction mode and a second candidate intra-prediction mode of a current block;
• encoding n-bit information specifying whether the intra-prediction mode of the current block is identical to the first candidate intra-prediction mode or the second candidate intra-prediction mode;
• when the intra-prediction mode of the current block is identical to one of the first candidate intra-prediction mode and the second candidate intra-prediction mode, encoding m-bit information specifying one of the first candidate intra-prediction mode and the second candidate intra-prediction mode identical to the intra-prediction mode of the current block;
• obtaining the intra-prediction mode of the current block, and
• obtaining prediction sample of the current block based on the intra-prediction mode of the current block,
• wherein deriving the first candidate intra-prediction mode and the second candidate intra-prediction mode comprises:
• deriving a first neighbor prediction mode based on a first neighbor block adjacent to the current block,
• wherein when the first neighbor block is available, the first neighbor prediction mode is set to as an intra-prediction mode of the first neighbor block, and
• wherein when the first neighbor block is unavailable, the first neighbor prediction mode is set to a DC mode;
• deriving a second neighbor prediction mode based on a second neighbor block adjacent to the current block,
• wherein when the second neighbor block is available, the second neighbor prediction mode is set to as an intra-prediction mode of the second neighbor block, and
• wherein when the second neighbor block is unavailable, the second neighbor prediction mode is set to a DC mode;
• and
• deriving the first candidate intra-prediction mode and the second candidate intra-prediction mode from the first neighbor prediction mode and the second neighbor prediction mode,
• wherein when the first neighbor prediction mode and the second neighbor prediction mode are different, the first candidate intra-prediction mode and the second candidate intra-prediction mode are determined without comparing values of the first neighbor prediction mode and the second neighbor prediction mode.