Method and apparatus for improved context design for prediction mode and coded block flag (CBF)

An apparatus for controlling intra-inter prediction for decoding or encoding of a video sequence, the apparatus comprising:

• at least one memory configured to store computer program code;
• and
• at least one processor configured to access the at least one memory and operate according to the computer program code, the computer program code comprising:
• setting code configured to cause the at least one processor to:
• set a prediction mode flag associated with a current block to indicate whether the current block is coded in inter prediction mode, intra prediction mode, or inter-intra prediction mode;
• derive a context value associated with a coded block flag associated with the current block based on the prediction mode flag associated with the current block, wherein the context value is based on at least two values, and wherein deriving the context value further comprises:
• based on the current block being determined to be coded in the intra prediction mode or intra-inter prediction mode, set the context value of the coded block flag to a first value,
• wherein a same context value of the coded block flag is used when the current block being coded in the intra prediction mode or intra-inter prediction mode, and
• based on the current block being determined to be coded in the inter prediction mode, set the context value of the coded block flag to a second value;
• and
• performing code configured to cause the at least one processor to perform entropy coding of a luma coded block flag associated with the current block using the context value, wherein a sampling structure for entropy coding of the video sequence is 4:2:0.

A non-transitory computer-readable storage medium storing instructions that cause at least one processor to:

• set a prediction mode flag associated with a current block to indicate whether the current block is coded in inter prediction mode, intra prediction mode, or inter-intra prediction mode;
• derive a context value associated with a coded block flag associated with the current block based on the prediction mode flag associated with the current block, wherein the context value is based on at least two values, and wherein deriving the context value further comprises:
• based on the current block being determined to be coded in the intra prediction mode or intra-inter prediction mode, set the context value of the coded block flag to a first value,
• wherein a same context value of the coded block flag is used when the current block being coded in the intra prediction mode or intra-inter prediction mode, and
• based on the current block being determined to be coded in the inter prediction mode, set the context value of the coded block flag to a second value;
• and
• perform entropy coding of a luma coded block flag associated with the current block using the context value, wherein a sampling structure for entropy coding of a video sequence is 4:2:0.