Binarization of dQP using Separate Absolute Value and Sign (SAVS) in CABAC
Video coding systems or apparatus utilizing context-based adaptive binary arithmetic coding (CABAC) during encoding and/or decoding, are configured according to the invention with an enhanced binarization of non-zero Delta-QP (dQP). During binarization the value of dQP and the sign are separately encoded using unary coding and then combined into a binary string which also contains the dQP non-zero flag. This invention capitalizes on the statistical symmetry of positive and negative values of dQP and results in saving bits and thus a higher coding efficiency.
1. A video encoding apparatus, comprising:
circuitry configured to:
set a difference quantization parameter as a difference between a quantization parameter of a current coding unit and a predicted quantization parameter of the current coding unit;
separate the difference quantization parameter into an absolute value of the difference quantization parameter and a sign indicating whether the difference quantization parameter is positive or negative;
sequentially encode the absolute value and the sign, wherein
the absolute value of the difference quantization parameter is mapped to a binary string using unary codes; and
generate bitstream as syntax in which the absolute value and the sign are written in order, wherein
an order of coding is, first, the binary string of the absolute value and, then, the sign.
2. The video encoding apparatus according to claim 1 , wherein the sign is encoded subsequent to encoding of the binary string of the absolute value.
3. A video encoding method, comprising:
setting a difference quantization parameter as a difference between a quantization parameter of a current coding unit and a predicted quantization parameter of the current coding unit;
separating the set difference quantization parameter into an absolute value of the difference quantization parameter and a sign indicating whether the difference quantization parameter is positive or negative;
sequentially encoding the absolute value and the sign, wherein
the absolute value of the difference quantization parameter is mapped to a binary string using unary codes; and
generating bitstream as syntax in which the absolute value and the sign are written in order, wherein
an order of coding is, first, the binary string of the absolute value and, then, the sign.
4. A video decoding apparatus, comprising:
a decoding unit configured to:
obtain an absolute value of a differential quantization parameter and a sign value of the differential quantization parameter from a bit stream, wherein
the differential quantization parameter is encoded such that the absolute value and the sign value are separated; and
decode the absolute value of the differential quantization parameter and the sign value of the differential quantization parameter in an order from the absolute value to the sign value, wherein
the differential quantization parameter is a difference between a quantization parameter of a current coding unit and a predicted quantization parameter of the current coding unit; and
an inverse quantizing unit configured to:
set the differential quantization parameter based on the decoded absolute value of the differential quantization parameter and the decoded sign value of the differential quantization parameter; and
inversely quantize quantized data, wherein the quantized data is based on decode of the bit stream using the quantization parameter of the current coding unit.
5. A video decoding method, comprising:
obtaining an absolute value of a differential quantization parameter and a sign value of the differential quantization parameter from a bit stream, wherein
the differential quantization parameter is encoded such that the absolute value and the sign value are separated; and
decoding the absolute value of the differential quantization parameter and the sign value of the differential quantization parameter in an order from the absolute value to the sign value, wherein
the differential quantization parameter is a difference between a quantization parameter of a current coding unit and a predicted quantization parameter of the current coding unit;
setting the differential quantization parameter based on the decoded absolute value of the differential quantization parameter and the decoded sign value of the differential quantization parameter; and
inversely quantizing quantized data, wherein the quantized data is based on decode of the bit stream using the quantization parameter of the current coding unit.