Methods and Apparatuses of Decoder Side Intra Mode Derivation

A method of processing video data in a video coding system, comprising:

• receiving input data associated with a current block of the video data by a video encoder or receiving input data associated with a current block from a video bitstream by a video decoder;
• determining a coarse grain intra prediction mode for the current block, wherein the coarse grain intra prediction mode is signaled explicitly in the video bitstream;
• applying decoder side intra mode derivation to refine the coarse grain intra prediction mode of the current block by evaluating a number of intra prediction modes associated with the coarse grain intra prediction mode, and selecting one intra prediction mode among the number of intra prediction modes as a refined mode according to the decoder side intra mode derivation;
• performing intra prediction for the current block based on the refined mode selected by the decoder side intra mode derivation;
• and
• encoding the current block to generate the video bitstream by the video encoder or decoding the current block to generate decoded video by the video decoder.

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

• receiving input data associated with a current block of the video data;
• determining an actual intra prediction mode for the current block by performing decoder side intra mode derivation, wherein the decoder side intra mode derivation is an intra mode derivation method that determines the actual intra prediction mode for the current block without referencing original samples of the current block;
• performing intra prediction for the current block based on the actual intra prediction mode;
• replacing the actual intra prediction mode determined by the decoder side intra mode derivation with a pseudo mode when referencing an intra prediction mode of the current block by an intra mode dependent tool;
• and
• encoding or decoding the current block.

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 data associated with a current block of the video data;
• determining an actual intra prediction mode for the current block by performing decoder side intra mode derivation, wherein the decoder side intra mode derivation is an intra mode derivation method that determines the actual intra prediction mode for the current block without referencing original samples of the current block;
• performing intra prediction for the current block based on the actual intra prediction mode;
• replacing the actual intra prediction mode determined by the decoder side intra mode derivation with a pseudo mode when referencing an intra prediction mode of the current block by an intra mode dependent tool;
• and
• encoding or decoding the current block.

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

• receiving input data associated with a current block of the video data by a video encoder or receiving input data associated with a current block from a video bitstream by a video decoder;
• determining a coarse grain intra prediction mode for the current block, wherein the coarse grain intra prediction mode is signaled explicitly in the video bitstream;
• applying decoder side intra mode derivation to refine the coarse grain intra prediction mode of the current block by evaluating a number of intra prediction modes associated with the coarse grain intra prediction mode, and selecting one intra prediction mode among the number of intra prediction modes as a refined mode according to the decoder side intra mode derivation, wherein the decoder side intra mode derivation is an intra mode derivation method that determines the actual intra prediction mode for the current block without referencing original samples of the current block;
• performing intra prediction for the current block based on the refined mode selected by the decoder side intra mode derivation;
• and
• encoding the current block to generate the video bitstream by the video encoder or decoding the current block to generate decoded video by the video decoder.

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 data associated with a current block of the video data by a video encoder or receiving input data associated with a current block from a video bitstream by a video decoder;
• determining a coarse grain intra prediction mode for the current block, wherein the coarse grain intra prediction mode is signaled explicitly in the video bitstream;
• applying decoder side intra mode derivation to refine the coarse grain intra prediction mode of the current block by evaluating a number of intra prediction modes associated with the coarse grain intra prediction mode, and selecting one intra prediction mode among the number of intra prediction modes as a refined mode according to the decoder side intra mode derivation, wherein the decoder side intra mode derivation is an intra mode derivation method that determines the actual intra prediction mode for the current block without referencing original samples of the current block;
• performing intra prediction for the current block based on the refined mode selected by the decoder side intra mode derivation;
• and
• encoding the current block to generate the video bitstream by the video encoder or decoding the current block to generate decoded video by the video decoder.