Intra prediction-based video encoding/decoding method and device

A method of encoding an image based on an intra prediction with an encoding apparatus, comprising:

• determining a reference pixel line for the intra prediction of a current block in the image;
• determining an intra prediction mode of the current block;
• obtaining a residual block of the current block based on an original block of the current block and a prediction block of the current block, the prediction block being obtained based on the reference pixel line and the intra prediction mode;
• and
• encoding the residual block to generate a bitstream the encoded image,
• wherein the current block includes a luma block and a chroma block, and the intra prediction mode of the current block is determined for the luma block and the chroma block, respectively,
• wherein an intra prediction mode of the chroma block belongs to one of a first mode group and a second mode group, the first mode group including only inter-components reference-based prediction modes, the second mode group including 67 intra prediction modes pre-defined in the encoding apparatus, the 67 intra prediction modes being composed of 2 non-directional modes and 65 directional modes, and
• wherein a flag for specifying whether the intra prediction mode of the chroma block belongs to the first mode group or the second mode group is encoded and is included in the bitstream.

A non-transitory computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to:

• determining a reference pixel line for the intra prediction of a current block in the image;
• determining an intra prediction mode of the current block;
• and
• predicting the current block based on the reference pixel line and the intra prediction mode,
• wherein the current block includes a luma block and a chroma block, and the intra prediction mode of the current block is determined for the luma block and the chroma block, respectively, and
• wherein determining an intra prediction mode of the chroma block comprises:
• selecting one of a first mode group and a second mode group based on a first flag signaled from the encoding apparatus, the first mode group including only inter-components reference-based prediction modes, the second mode group including 67 intra prediction modes pre-defined in the decoding apparatus, the 67 intra prediction modes being composed of 2 non-directional modes and 65 directional modes, and the first flag specifying whether the intra prediction mode of the chroma block belongs to the first mode group or the second mode group;
• and
• deriving the intra prediction mode of the chroma block from the selected one.