Method and Apparatus of Encoding or Decoding Video Data with Intra Prediction Mode Mapping

An apparatus of processing video data in a video coding system, the apparatus comprising one or more electronic circuits configured for:

• receiving input video data associated with a current chroma block in a current picture coded in a 4:2:2 color format;
• determining a luma mode of a luma block corresponding to the current chroma block;
• mapping the luma mode to a mapped intra mode for the current chroma block, wherein the mapped intra mode is mode 57 when the luma mode is mode 61 and the mapped intra mode is mode 55 when the luma mode is mode 57;
• selectively replacing the mapped intra mode by Wide Angle Intra Prediction (WAIP) mode mapping based on a width to height ratio of the current chroma block;
• deriving an intra predictor for the current chroma block according to the mapped intra mode after WAIP mode mapping;
• and
• encoding or decoding the current chroma block according to the intra predictor.

A non-transitory computer readable medium storing program instruction causing a processing circuit of an apparatus to perform video processing method, and the method comprising:

• receiving input video data associated with a current chroma block in a current picture coded in a 4:2:2 color format;
• determining a luma mode of a luma block corresponding to the current chroma block;
• mapping the luma mode to a mapped intra mode for the current chroma block, wherein the mapped intra mode is mode 57 when the luma mode is mode 61 and the mapped intra mode is mode 55 when the luma mode is mode 57;
• selectively replacing the mapped intra mode by Wide Angle Intra Prediction (WAIP) mode mapping based on a width to height ratio of the current chroma block;
• deriving an intra predictor for the current chroma block according to the mapped intra mode after WAIP mode mapping;
• and
• encoding or decoding the current chroma block according to the intra predictor.