Image decoding device, image encoding device, and method thereof using a prediction quantization parameter
A lossless decoding unit 52 takes quantization parameters of decoded blocks spatially or temporally adjacent to a block to be decoded, as selection candidates, and extracts, from stream information, difference information indicating difference as to a prediction quantization parameter selected from the selection candidates. A quantization parameter calculating unit 59 calculates, from the prediction quantization parameter and the difference information, a quantization parameter of the block to be decoded. Thus, decoding of the image can be performed correctly by calculating a quantization parameter equal to a quantization parameter used at the time of image encoding.
1. An image encoding method, comprising:
setting, if a block adjacent to the left of a current block and a block adjacent above the current block are available, a prediction quantization parameter derived from an average value of a quantization parameter of the block adjacent to the left and a quantization parameter of the block adjacent above;
setting, if the block adjacent to the left and the block adjacent above are not available, the prediction quantization parameter derived from a quantization parameter of a processing unit not adjacent to the current block;
generating a difference information indicating a difference between the set prediction quantization parameter and a quantization parameter of the current block; and
generating stream information including the difference information.
2. The image encoding method of claim 1 ,
wherein the quantization parameter of the processing unit not adjacent to the current block is an initial value of a quantization parameter in a slice.
3. The image encoding method of claim 1 ,
wherein, if the block adjacent to the left and the block adjacent above are not available, a quantization parameter of a previous block is derived to set the prediction quantization parameter.
4. The image encoding method of claim 1 ,
wherein the block is a coding unit, and the coding unit has a hierarchical structure defined by a hierarchical depth.
5. The image encoding method of claim 4 , further comprising:
performing a quantization by a transform unit included in the coding unit, based on the quantization parameter of the current block.
6. The image encoding method of claim 1 , further comprising:
encoding the difference information.
7. An information processing apparatus comprising:
a circuitry configured to:
set, if a block adjacent to the left of a current block and a block adjacent above the current block are available, a prediction quantization parameter derived from an average value of a quantization parameter of the block adjacent to the left and a quantization parameter of the block adjacent above;
set, if the block adjacent to the left and the block adjacent above are not available, the prediction quantization parameter derived from a quantization parameter of a processing unit not adjacent to the current block;
generate a difference information indicating a difference between the set prediction quantization parameter and a quantization parameter of the current block; and
generate stream information including the difference information.
8. The information processing apparatus of claim 7 , wherein the quantization parameter of the processing unit not adjacent to the current block is an initial value of a quantization parameter in a slice.
9. The information processing apparatus of claim 7 , wherein, if the block adjacent to the left and the block adjacent above are not available, a quantization parameter of a previous block is derived to set the prediction quantization parameter.
10. The information processing apparatus of claim 7 , wherein the block is a coding unit, and the coding unit has a hierarchical structure defined by a hierarchical depth.
11. The information processing apparatus of claim 10 , wherein the processing circuitry is further configured to:
perform a quantization by a transform unit included in the coding unit, based on the calculated quantization parameter of the current block.
12. The information processing apparatus of claim 7 , wherein the processing circuitry is further configured to:
encode the difference information.