Method for determining color difference component quantization parameter and device using the method
View Patent ↗Disclosed are a method for determining a color difference component quantization parameter and a device using the method. Method for decoding an image can comprise the steps of: decoding a color difference component quantization parameter offset on the basis of size information of a transform unit; and calculating a color difference component quantization parameter index on the basis of the decoded color difference component quantization parameter offset. Therefore, the present invention enables effective quantization by applying different color difference component quantization parameters according to the size of the transform unit when executing the quantization.
1. A video decoding apparatus comprising:
an inverse-quantizer configured to determine a size of a quantization group, the quantization group being a group of a plurality of transform blocks to which a same chrominance component quantization parameter is applied, configured to calculate the chrominance component quantization parameter applied to the determined quantization group, and configured to inverse-quantize transform coefficients of a transform block included in the determined quantization group by using the calculated chrominance component quantization parameter; and
an inverse-transformer configured to generate a residual block by inverse-transforming the inverse-quantized transform coefficients,
wherein the inverse-quantizer comprises:
a chrominance component quantization parameter index calculator configured to calculate a chrominance component quantization parameter index by using both a first chrominance component quantization parameter offset of a picture level and a second chrominance component quantization parameter offset of a slice level, the first chrominance component quantization parameter offset being extracted from a picture parameter set of a bitstream, and the second chrominance component quantization parameter offset being extracted from a slice header of the bitstream; and
a chrominance component quantization parameter calculator configured to calculate the chrominance component quantization parameter based on the chrominance component quantization parameter index.
2. The video decoding apparatus of claim 1 , wherein the quantization group includes the transform blocks having different sizes.
3. The video decoding apparatus of claim 1 , wherein the chrominance component quantization parameter index is calculated by adding the first chrominance component quantization parameter offset and the second chrominance component quantization parameter offset to a luminance component quantization parameter.