Method and for reconstructing chroma block and video decoding apparatus
A method and for reconstructing chroma blocks and a video decoding apparatus are disclosed. In accordance with one aspect of the present disclosure, provided is a method for reconstructing a chroma block of a target block to be reconstructed. The method includes decoding correlation information between first residual samples and second residual samples, the first residual sample, and prediction information of the chroma block from a bitstream, wherein the first residual samples are residual samples of a first chroma component and the second residual samples are residual samples of a second chroma component. The method further includes generating predicted samples of the first chroma component and predicted samples of the second chroma information on the basis of the prediction information, and deriving the second residual samples by applying the correlation information to the first residual samples. The method further includes reconstructing a chroma block of the first chroma component by adding the first residual samples and the predicted samples of the first chroma component and reconstructing a chroma block of the second chroma component by adding the second residual samples and predicted samples of the second chroma component.
1. A video decoding apparatus for reconstructing a chroma block of a target block to be reconstructed, the video decoding apparatus comprising:
a decoder configured to decode correlation information between first residual samples and second residual samples, the first residual samples, and prediction information of the chroma block from a bitstream, wherein the first residual samples are residual samples of a first chroma component and the second residual samples are residual samples of a second chroma component;
a predictor configured to generate predicted samples of the first chroma component and predicted samples of the second chroma information on the basis of the prediction information;
a chroma component reconstruction unit configured to derive the second residual samples by applying the correlation information to the first residual samples; and
an adder configured to reconstruct a chroma block of the first chroma component by adding the first residual samples and the predicted samples of the first chroma component and configured to reconstruct a chroma block of the second chroma component by adding the second residual samples and predicted samples of the second chroma component.
2. The video decoding apparatus of claim 1 , wherein the first chroma component is one of a Cb chroma component and a Cr chroma component, and the second chroma component is the other of the Cb chroma component and the Cr chroma component.
3. The video decoding apparatus of claim 1 , wherein the decoder is further configured to decode the correlation information from a picture level of the bitstream.
4. The video decoding apparatus of claim 1 , wherein
the correlation information includes multiplication information for indicating a multiplication factor between the first residual samples and the second residual samples, and
the chroma component reconstruction unit is further configured to derive the second residual samples by applying a multiplication factor indicated by the multiplication information to the first residual samples.
5. The video decoding apparatus of claim 4 , wherein
the correlation information further includes offset information for indicating an offset factor between the first residual samples and the second residual samples, and
the chroma component reconstruction unit is configured to derive the second residual samples by applying an offset factor indicated by the offset information to the first residual samples to which the multiplication factor is applied.
6. The video decoding apparatus of claim 1 , wherein
the decoder is further configured to:
decode a first syntax element indicating whether derivation of the second residual samples is allowed from a sequence parameter set (SPS) level of the bitstream; and
decode a second syntax element indicating whether the derivation of the second residual samples is applied to the chroma block from a level lower than the SPS level in the bitstream when the first syntax element indicates that the derivation of the second residual samples is allowed, and
the chroma component reconstruction unit is further configured to derive the second residual samples when the second syntax element indicates that the derivation of the second residual samples is applied to the chroma block.
7. The video decoding apparatus of claim 6 , wherein the decoder is further configured to decode the second syntax element in consideration of a predictive mode of the target block.