Multiple direct mode for intra coding

In this paper, a multiple direct mode (MDM) method is presented for chroma intra coding. The main contributions of the proposed MDM method include two aspects: selection of multiple luma intra prediction modes from co-located luma blocks, and the derivation of chroma intra prediction modes from spatial neighbouring blocks. With the proposed method, both the cross-component correlation and spatial correlation of intra prediction modes can be better utilized for more efficient chroma intra coding. Simulation results have validated the efficiency of MDM especially under the decoupled luma-chroma partition trees. The proposed method has been adopted in the Joint Exploration Model (JEM) which is the test platform for future video coding technology exploration in Joint Video Exploration Team (JVET).