Method and apparatus for encoding/decoding image
A method for decoding an image, according to the present invention, comprises the steps of: receiving image information that corresponds to a block to be decoded; performing entropy-decoding with respect to the image information that is received; deciding a transform skip mode of the block to be decoded from a plurality of transform skip mode candidates, based on the image information that is entropy-decoded; and reverse-transforming the block to be decoded based on the transform skip mode that is decided.
1. A method of decoding a video signal having a current block to be decoded with a decoding apparatus, comprising:
obtaining residual coefficients relating to the current block from the video signal;
obtaining inverse-quantized residual coefficients by inverse-quantizing the residual coefficients;
determining, based on a transform skip mode index specifying a transform skip mode of the current block, the transform skip mode of the current block,
wherein the transform skip mode of the current block is determined to be one of one or more transform skip mode candidates,
wherein the one or more transform skip mode candidates include at least one of a 2D transform mode, a horizontal transform mode, a vertical transform mode or a non-transform mode, and
wherein a number of the one or more transform skip mode candidates is different according to a size or a shape of the current block;
obtaining, based on the determined transform skip mode of the current block, residual samples from the inverse-quantized residual coefficients;
obtaining prediction samples of the current block by using motion information of the current block; and
reconstructing the current block by using the residual samples and the prediction samples,
wherein when the transform skip mode of the current block is determined to be the non-transform mode, the residual samples are obtained by scaling the inverse-quantized residual coefficients in non-transformed rows and/or columns of the current block with a predetermined value.
2. The method of claim 1 , wherein the scaling is performed using a bit shift operation.
3. The method of claim 1 , wherein the transform skip mode index is transmitted, from an encoding apparatus, by a transform unit.
4. The method of claim 1 , wherein the 2D transform mode performs both a horizontal transform and a vertical transform, the horizontal transform mode performs the horizontal transform only without the vertical transform, the vertical transform mode performs the vertical transform only without the horizontal transform, and the non-transform mode performs none of the horizontal transform and the vertical transform.
5. The method of claim 1 , wherein the motion information includes a motion vector and a reference index.
6. An apparatus of decoding a video signal having a current block to be decoded, comprising:
a decoding apparatus configured to:
obtain residual coefficients relating to the current block from the video signal;
obtain inverse-quantized residual coefficients by inverse-quantizing the residual coefficients;
determine, based on a transform skip mode index specifying a transform skip mode of the current block, the transform skip mode of the current block,
wherein the transform skip mode of the current block is determined to be one of one or more transform skip mode candidates,
wherein the one or more transform skip mode candidates including at least one of a 2D transform mode, a horizontal transform mode, a vertical transform mode or a non-transform mode, and
wherein a number of the one or more transform skip mode candidates is different according to a size or a shape of the current block;
obtain, based on the determined transform skip mode of the current block, residual samples from the inverse-quantized residual coefficients;
obtain prediction samples of the current block by using motion information of the current block; and
reconstruct the current block by using the residual samples and the prediction samples,
wherein when the transform skip mode of the current block is determined to be the non-transform mode, the residual samples are obtained by scaling the inverse-quantized residual coefficients in non-transformed rows and/or columns of the current block with a predetermined value.
7. The apparatus of claim 6 , wherein the scaling is performed using a bit shift operation.
8. The apparatus of claim 6 , wherein the transform skip mode index is transmitted, from an encoding apparatus, by a transform unit.
9. The apparatus of claim 6 , wherein the 2D transform mode performs both a horizontal transform and a vertical transform, the horizontal transform mode performs the horizontal transform only without the vertical transform, the vertical transform mode performs the vertical transform only without the horizontal transform, and the non-transform mode performs none of the horizontal transform and the vertical transform.
10. The apparatus of claim 6 , wherein the motion information includes a motion vector and a reference index.