Context reduction for context adaptive binary arithmetic coding
A reduction in the number of binarizations and/or contexts used in context adaptive binary arithmetic coding (CABAC) for video coding is proposed. In particular, this disclosure proposes techniques that may lower the number contexts used in CABAC by up to 56.
1. A method of encoding video data comprising:
determining a prediction type for a block of video data in a slice,
wherein the slice is one of an intra (I), predictive (P), or bi-predictive (B) slice;
representing the prediction type as a slice prediction type syntax element;
binarizing the slice prediction type syntax element using a first binarization mapping when the slice is a P or B slice and a second, different, binarization mapping when the slice is an I slice;
context adaptive binary arithmetic encoding (CABAC) the binarized slice prediction type syntax element;
wherein the prediction type syntax element specifies a prediction mode and a partition type; and
encoding the block of video data in the slice.
2. The method of claim 1 , wherein the partition type includes one of symmetric partitions and asymmetric partitions.
3. A method of decoding video data comprising:
context adaptive binary arithmetic decoding a slice prediction type syntax element which indicates the prediction type for a block of video data in a slice to produce a binarized slice prediction type syntax element,
wherein the slice is one of an intra (I), predictive (P), or bi-predictive (B) slice;
mapping a binarized slice prediction type syntax element to a prediction type using a first binarization mapping when the slice is a P or B slice and a second, different, binarization mapping when the slice is an I slice;
wherein the slice prediction type syntax element specifies a prediction mode and a partition type; and
decoding the block of video data based on the mapped prediction type for the slice.
4. The method of claim 3 , wherein the partition type includes one of symmetric partitions and asymmetric partitions.
5. An apparatus for decoding video data comprising:
a memory configured to store video data; and
a video decoder in communication with the memory and configured to:
context adaptive binary arithmetic decode a slice prediction type syntax element which indicates the prediction type for a block of video data in a slice to produce a binarized slice prediction type syntax element,
wherein the slice is one of an intra (I), predictive (P), or bi-predictive (B) slice;
map a binarized slice prediction type syntax element to a prediction type using a first binarization mapping when the slice is a P or B slice and a second, different, binarization mapping when the slice is an I slice;
wherein the slice prediction type syntax element specifies a prediction mode and a partition type; and
decode the block of video data based on the mapped prediction type for the slice.
6. The apparatus of claim 5 , wherein the partition type includes one of symmetric partitions and asymmetric partitions.
7. The apparatus of claim 5 , further comprising a display device in communication with the processor and configured to decode the video bitstream.
8. The apparatus of claim 7 , further comprising at least one of a desktop computer, a laptop computer, a smartphone, a tablet computer, a television, a set-top box, a video gaming console, or a digital media player.
9. The apparatus of claim 5 , further comprising a receiver in communication with the processor and configured to receive the video bitstream over a communication channel.