Method and apparatus for encoding video, and decoding method and apparatus based on quantization parameter
The present invention relates to a video encoding method and apparatus for setting and encoding quantization parameters, and to a video decoding method and apparatus for decoding and setting quantization parameters in a video encoding and decoding apparatus which uses blocks having various sizes and depths as encoding and decoding units.
1. A method for decoding an image, the method comprising:
receiving a bitstream including image information;
decoding base block size information on a size of a base block from the bitstream;
decoding a residual quantization parameter of a decoding object unit from the bitstream; and
determining a quantization parameter of the decoding object unit based on the residual quantization parameter and a predicted quantization parameter,
wherein when a size of the decoding object unit is smaller than a size of the base block specified by the base block size information, the quantization parameter of the decoding object unit is same as quantization parameters of all the other decoding units included in the base block together with the decoding object unit.
2. The method of claim 1 , wherein the base block size information is obtained by a Picture Parameter Set and the residual quantization parameter is obtained for a transform unit TU.
3. The method of claim 1 , wherein the residual quantization parameter is decoded according to a quantization parameter flag information, the quantization parameter flag information specifying whether the residual quantization parameter is present in the bitstream.
4. The method of claim 1 , wherein the predicted quantization parameter is determined based on an average value of already decoded quantization parameters.
5. The method of claim 1 , wherein the already decoded quantization parameters comprise quantization parameters of neighboring blocks adjacent to the base block, and
wherein the neighboring blocks comprise a block located upper side of the base block and a block located left side of the base block.
6. The method of claim 1 , wherein, when the size of the decoding object unit is smaller than the size of the base block, the predicted quantization parameter of the decoding object unit has a same value as a predicted quantization parameter of another decoding units included in the base block together with the decoding object unit.
7. The method of claim 1 , wherein the residual quantization parameter is decoded when the decoding object unit has a first order among a plurality of units included in the base block.