Chroma Intra Mode Selection Using Luma-Linked Direct Mode

The patent segments the intra prediction mode selection process into two distinct parts: luma component prediction and chroma component prediction. This segmentation allows independent optimization of prediction modes for each color component, enabling more efficient coding by selecting appropriate prediction modes based on the specific characteristics of each component rather than using a unified approach.

The patent applies local quality by allowing different prediction modes to be used for luma and chroma blocks based on their respective characteristics. The chroma block can use direct mode (DM) when the corresponding luma block uses intra prediction mode, creating a localized adaptation to the specific prediction mode requirements of each color component in different spatial regions.

The patent implements a dynamic candidate mode configuration strategy where the set of candidate intra modes for chroma blocks is not fixed but adapts based on the prediction mode used for the corresponding luma block. When luma uses intra prediction mode, chroma candidates include direct mode (DM); otherwise, alternative modes are selected. This dynamic adaptation optimizes prediction accuracy while avoiding the constant overhead of evaluating all possible modes in every case.

The patent changes the parameter of candidate mode selection based on the luma prediction mode parameter. By conditioning the chroma candidate mode configuration on the luma mode parameter, the system dynamically adjusts the search space and evaluation criteria, achieving higher prediction accuracy when needed while reducing complexity when standard modes suffice.