Decoding device, decoding method, encoding device, and encoding method

1. A decoding device comprising:

circuitry configured to

decode a bit stream and generate a quantized value,

determine a minimum block size for which a transform skip is configured to be performed on a transform block,

determine, for each transform block of a plurality of transform blocks in the bit stream, whether the transform skip is performed on the basis of a transform skip flag,

inversely quantize the generated quantized value by using a flat scaling list corresponding to the minimum block size for each transform block that is the minimum block size,

inversely quantize the generated quantized value using a non-flat matrix as a default scaling list for each transform block larger than the minimum block size when a value of the transform skip flag is 0, indicating that the transform skip is not performed, and

inversely quantize the generated quantized value by using a flat scaling list corresponding to a block size larger than the minimum block size instead of the default scaling list for each transform block larger than the minimum block size when the value of the transform skip flag is 1, indicating that the transform skip is performed,

wherein the minimum block size is a 4 by 4 block size,

wherein the value of the transform skip flag is based on a cost function value, and

wherein the flat scaling list had a quantization scaling factor set to a calue of 16.

2. The decoding device according to claim 1 , wherein when the block size of the transform block to which the transform skip is applied is an 8 by 8 block size and the value of the transform skip flag is 1, the generated quantized value is inversely quantized by using a flat scaling list of an 8 by 8 block size.

3. The decoding device according to claim 1 , wherein when the block size of the transform block to which the transform skip is applied is a 16 by 16 block size and the value of the transform skip flag is 1, the generated quantized value is inversely quantized by using a flat scaling list of a 16 by 16 block size.

4. The decoding device according to claim 1 , wherein when the block size of the transform block to which the transform skip is applied is a 32 by 32 block size and the value of the transform skip flag is 1, the generated quantized value is inversely quantized by using a flat scaling list of a 32 by 32 block size.

5. The decoding device according to claim 1 , wherein

the bit stream includes a residual data obtained by encoding a residual between an image and a prediction image of the image, and

the circuitry is further configured to decode the residual data and generate the quantized value.

6. The decoding device according to claim 1 , wherein the transform block is obtained by dividing, four times, a coding block in a recursive manner.

7. A decoding method, implemented via a processor of a decoding device, the method comprising:

decoding a bit stream and generating a quantized value;

determining a minimum block size for which a transform skip is configured to be performed on a transform block;

determining, for each transform block of a plurality of transform blocks in the bit stream, whether the transform skip is performed on the basis of a transform skip flag;

inversely quantizing the generated quantized value by using a flat scaling list corresponding to the minimum block size for each transform block that is the minimum block size;

inversely quantizing the generated quantized value using a non-flat matrix as a default scaling list for each transform block larger than the minimum block size when a value of the transform skip flag is 0, indicating that the transform skip is not performed; and

inversely quantizing the generated quantized value by using a flat scaling list corresponding to a block size larger than the minimum block size instead of the default scaling list for each transform block larger than the minimum block size when the value of the transform skip flag is 1, indicating that the transform skip is performed,

wherein the minimum block size is a 4 by 4 block size,

wherein the value of the transform skip flap is based on a cost function value, and

wherein the flat scaling list had a quantization scaling factor set to a calue of 16.

8. The decoding device according to claim 1 , wherein when the transform skip flag is 1 and the block size of the transform block is larger than the 4 by 4 block size, the circuitry inversely quantizes the generated quantized value by using the flat scaling list that is determined according to the block size of the transform block.

9. The decoding device according to claim 1 ,

wherein the value of the transform skip flag is determined to be 0 in a case where the cost function value associated with a case of not performing the transform skip is less than the cost function value associated with a case of performing the transform skip, and

wherein the value of the transform skip flag is determined to be 1 in a case where the cost function value associated with a case of not performing the transform skip is equal to or greater than the cost function value associated with a case of performing the transform skip.