Context design for prediction mode and CBF

1 . A method of intra-inter prediction for encoding a video sequence, the method being performed by at least one processor, and the method comprising:

determining whether a neighboring block of a current block is coded by an intra-inter prediction mode;

based on the neighboring block being determined to be coded by the intra-inter prediction mode, setting a prediction mode flag associated with the neighboring block;

determining a context value based on the prediction mode flag associated with the neighboring block;

incrementing a context index of a prediction mode flag associated with the current block by 0.5 or one based on determining that the neighboring block is coded by the intra-inter prediction mode;

determining an average context index based on the incremented context index and a number of neighboring blocks of the current block; and

using the context value and the average context index, encoding the prediction mode flag associated with the current block indicating that the current block is intra-coded.

2 . An apparatus for intra-inter prediction for decoding 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:

first determining code configured to cause the at least one processor to determine whether a neighboring block of a current block is coded by an intra-inter prediction mode;

first decoding code configured to cause the at least one processor to, based on the neighboring block being determined to be coded by the intra-inter prediction mode, decode a prediction mode flag associated with the neighboring block;

first deriving code configured to cause the at least one processor to obtain a context value based on the prediction mode flag associated with the neighboring block;

second determining code configured to cause the at least one processor to determine that a context index of a prediction mode flag associated with the current block is incremented by 0.5 or one based on determining that the neighboring block is coded by the intra-inter prediction mode;

third determining code configured to cause the at least one processor to determine an average context index based on the incremented context index and a number of neighboring blocks of the current block; and

second decoding code configured to cause the at least one processor to use the context value and the average context index to decode the prediction mode flag associated with the current block indicating that the current block is intra-coded.

3 . The method of claim 1 , wherein the setting the prediction mode flag associated with the neighboring block comprises setting the prediction mode flag associated with the neighboring block to indicate that the neighboring block is intra-coded; or

setting the prediction mode flag associated with the neighboring block comprises setting the prediction mode flag associated with the neighboring block to indicate that the neighboring block is inter coded.

4 . The method of claim 1 , further comprising:

determining whether the neighboring block is coded by an intra prediction mode or an inter prediction mode;

incrementing the context index of the prediction mode flag associated with the current block by a first value based on determining that the neighboring block is coded by the intra prediction mode;

incrementing the context index of the prediction mode flag associated with the current block by a second value based on determining that the neighboring block is coded by the inter prediction mode; and

incrementing the context index of the prediction mode flag associated with the current block by a third value based on determining the neighboring block is coded by the intra-inter prediction mode.

5 . The method of claim 1 , further comprising:

determining whether the neighboring block is coded by an intra prediction mode or an inter prediction mode;

incrementing the context index of the prediction mode flag associated with the current block by two based on determining that the neighboring block is coded by the intra prediction mode;

incrementing the context index of the prediction mode flag associated with the current block by zero based on determining that the neighboring block is coded by the inter prediction mode; and

setting the prediction mode flag associated with the current block based on the average context index.

6 . The method of claim 1 , wherein the method further comprises:

determining whether the neighboring block is coded by an intra prediction mode or an inter prediction mode;

incrementing the context index of the prediction mode flag associated with the current block by one based on determining that the neighboring block is coded by the intra prediction mode;

incrementing the context index by zero based on determining that the neighboring block is coded by the inter prediction mode; and

setting the prediction mode flag associated with the current block based on the average context index.

7 . The method of claim 1 , wherein the method further comprises:

encoding a coded block flag associated with the current block to have a first context when the current block is coded by an intra prediction mode;

encoding the coded block flag associated with the current block to have a second context value when the current block is coded by an inter prediction mode; and

encoding the coded block flag associated with the current block to have a third context value when the current block is coded by the intra-inter prediction mode.

8 . The apparatus of claim 2 , wherein the decoding the prediction mode flag associated with the neighboring block comprises decoding the prediction mode flag associated with the neighboring block to indicate that the neighboring block is intra-coded; or

decoding the prediction mode flag associated with the neighboring block comprises decoding the prediction mode flag associated with the neighboring block to indicate that the neighboring block is inter coded.

9 . The apparatus of claim 2 , wherein the computer program code further comprises:

determining whether the neighboring block is coded by an intra prediction mode or an inter prediction mode;

determining that the context index of the prediction mode flag associated with the current block is incremented by a first value based on determining that the neighboring block is coded by the intra prediction mode;

determining that the context index of the prediction mode flag associated with the current block is incremented by a second value based on determining that the neighboring block is coded by the inter prediction mode; and

determining that the context index of the prediction mode flag associated with the current block is incremented by a third value based on determining the neighboring block is coded by the intra-inter prediction mode.

10 . The apparatus of claim 2 , wherein the computer program code further comprises:

determining whether the neighboring block is coded by an intra prediction mode or an inter prediction mode;

determining that the context index of the prediction mode flag associated with the current block is incremented by two based on determining that the neighboring block is coded by the intra prediction mode;

determining that the context index of the prediction mode flag associated with the current block is incremented zero based on determining that the neighboring block is coded by the inter prediction mode; and

deriving the prediction mode flag associated with the current block based on the average context index.

11 . The apparatus of claim 2 , wherein the computer program code further comprises:

determining whether the neighboring block is coded by an intra prediction mode or an inter prediction mode;

determining that the context index of the prediction mode flag associated with the current block is incremented by one based on determining that the neighboring block is coded by the intra prediction mode;

determining that the context index is incremented by zero based on determining that the neighboring block is coded by the inter prediction mode; and

deriving the prediction mode flag associated with the current block based on the average context index.

12 . The method of claim 1 , wherein an intra prediction mode associated with the intra-inter prediction mode is a planar mode;

wherein the intra prediction mode associated with the intra-inter prediction mode is a DC mode; or

wherein the intra prediction mode associated with the intra-inter prediction mode is the intra prediction mode applied in the intra-inter prediction mode.

13 . The apparatus of claim 2 , wherein an intra prediction mode associated with the intra-inter prediction mode is a planar mode;

wherein the intra prediction mode associated with the intra-inter prediction mode is a DC mode; or

wherein the intra prediction mode associated with the intra-inter prediction mode is the intra prediction mode applied in the intra-inter prediction mode.

14 . The method of encoding video data of claim 2 , wherein an intra prediction mode associated with the intra-inter prediction mode is a planar mode;

wherein the intra prediction mode associated with the intra-inter prediction mode is a DC mode; or

wherein the intra prediction mode associated with the intra-inter prediction mode is the intra prediction mode applied in the intra-inter prediction mode.

15 . A non-transitory computer-readable storage medium storing instructions and a video bitstream that are generated by a video encoding method, the instructions, when executed by a computer, cause the computer to implement a video encoding method comprising:

determining whether a neighboring block of a current block is coded by an intra-inter prediction mode;

based on the neighboring block being determined to be coded by the intra-inter prediction mode, determining a prediction mode flag associated with the neighboring block;

determining a context value based on the prediction mode flag associated with the neighboring block;

incrementing a context index of a prediction mode flag associated with the current block by 0.5 or one based on determining that the neighboring block is coded by the intra-inter prediction mode;

determining an average context index based on the incremented context index and a number of neighboring blocks of the current block;

using the context value and the average context index to process the prediction mode flag associated with the current block indicating that the current block is intra-coded; and

transmitting the video bitstream.