Image processing apparatus and method

1. A method for processing an image performed by an image processing apparatus, the method comprising:

decoding a bit stream to generate quantized data, the bit stream including a flag, for each block, that specifies whether or not a difference quantization parameter is present in the bit stream, and the flag being included in a first layer that is higher than a second layer in which the difference quantization parameter is set;

setting, by processing circuitry of the image processing apparatus according to the flag, a current quantization parameter for a current sub block formed by block partitioning, which splits a block into smaller sub blocks; and

inversely quantizing, by the processing circuitry, the generated quantized data using the set current quantization parameter.

2. The method according to claim 1 , wherein the setting comprises:

setting the current quantization parameter for the current sub block using a value indicating a minimum sub block size for which the difference quantization parameter is set.

3. The method according to claim 2 , wherein the difference quantization parameter is a difference value between the current quantization parameter for the current sub block and a previous quantization parameter for a previous sub block.

4. The method according to claim 3 , wherein the previous sub block is a sub block that is decoded immediately before the current sub block in the order the bit stream is decoded.

5. The method according to claim 1 , wherein the difference quantization parameter is a difference value between the current quantization parameter set for the current sub block and a current slice quantization parameter set for a current slice.

6. The method according to claim 1 , further comprising:

acquiring the flag as a syntax of the bit stream.

7. The method according to claim 1 , wherein

the block is a largest coding unit (LCU) and the sub block is a coding unit, and

the LCU is recursively split into the coding units.

8. An image processing apparatus, comprising:

processing circuitry configured to

decode a bit stream to generate quantized data, the bit stream including a flag, for each block, that specifies whether or not a difference quantization parameter is present in the bit stream, and the flag being included in a first layer that is higher than a second layer in which the difference quantization parameter is set;

set, according to the flag, a current quantization parameter for a current sub block formed by block partitioning, which splits a block into smaller sub blocks; and

inversely quantize the generated quantized data using the set current quantization parameter.

9. The image processing apparatus according to claim 8 , wherein the processing circuitry is configured to

set the current quantization parameter for the current sub block using a value indicating a minimum sub block size for which the difference quantization parameter is set.

10. The image processing apparatus according to claim 8 , wherein the difference quantization parameter is a difference value between the current quantization parameter for the current sub block and a previous quantization parameter for a previous sub block.

11. The image processing apparatus according to claim 10 , wherein the previous sub block is a sub block that is decoded immediately before the current sub block in the order the bit stream is decoded.

12. The image processing apparatus according to claim 8 , wherein the difference quantization parameter is a difference value between the current quantization parameter set for the current sub block and a current slice quantization parameter set for a current slice.

13. The image processing apparatus according to claim 8 , wherein the processing circuitry is configured to

acquire the flag as a syntax of the bit stream.

14. The image processing apparatus according to claim 8 , wherein

the block is a largest coding unit (LCU) and the sub block is a coding unit, and

the LCU is recursively split into the coding units.