Context initialization based on slice header flag and slice type
Technique for initialization of encoders and decoders. In some cases, the decoder receives a slice and identifies if the slice is either a forward predicted B-slice or a backward predicted B-slice, and not both a forward and backward predicted B-slice, and based upon this identification initializes, using a P-slice technique, a context associated with the slice.
1. A method for decoding a video frame, the method comprising:
receiving a bitstream of encoded video data;
decoding, from the bitstream, a syntax element indicative of a slice type of a slice;
when the slice type indicates a B slice type or a P slice type, decoding, from the bitstream, a flag that is used to determine a Context-Adaptive Binary Arithmetic Coding (CABAC) context initialization method for the B slice type or the P slice type; and
initializing a CABAC context associated with the slice type, wherein
in a case that the slice type indicates the B slice type and a value of the flag is equal to a first value, a CABAC context associated with the B slice type is initialized by a first initialization method,
in a case that the slice type indicates the B slice type and the value of the flag is equal to a second value, a CABAC context associated with the B slice type is initialized by a second initialization method,
in a case that the slice type indicates the P slice type and the value of the flag is equal to the first value, a CABAC context associated with the P slice type is initialized by the second initialization method,
in a case that the slice type indicates the P slice type and the value of the flag is equal to the second value, a CABAC context associated with the P slice type is initialized by the first initialization method, and
in a case that the slice type indicates an I slice type, a CABAC context associated with the I slice type is initialized by a third initialization method.
2. The method of claim 1 , further comprising:
decoding the video frame; and
displaying the decoded video frame.
3. The method of claim 1 , further comprising:
decoding the bitstream of encoded video data; and
displaying the decoded video data.
4. An apparatus for decoding a video frame, the apparatus comprising a processor and memory, the processor, working together with the memory, being configured to:
receive a bitstream of encoded video data;
decode, from the bitstream, a syntax element indicative of a slice type of a slice;
when the slice type indicates a B slice type or a P slice type, decode, from the bitstream, a flag that is used to determine a Context-Adaptive Binary Arithmetic Coding (CABAC) context initialization method for the B slice type or the P slice type; and
initialize a CABAC context associated with the slice type, wherein
in a case that the slice type indicates the B slice type and a value of the flag is equal to a first value, a CABAC context associated with the B slice type is initialized by a first initialization method,
in a case that the slice type indicates the B slice type and the value of the flag is equal to a second value, a CABAC context associated with the B slice type is initialized by a second initialization method,
in a case that the slice type indicates the P slice type and the value of the flag is equal to the first value, a CABAC context associated with the P slice type is initialized by the second initialization method,
in a case that the slice type indicates the P slice type and the value of the flag is equal to the second value, a CABAC context associated with the P slice type is initialized by the first initialization method, and
in a case that the slice type indicates an I slice type, a CABAC context associated with the I slice type is initialized by a third initialization method.
5. The apparatus of claim 4 wherein the processor, working together with the memory, is further configured to:
decode the video frame; and
display the decoded video frame.
6. The apparatus of claim 4 , wherein the processor, working together with the memory, is further configured to:
decode the bitstream of encoded video data; and
display the decoded video data.