Method and apparatus for deriving intra prediction mode for chroma component

1. A method of decoding a chroma block of a video signal by an apparatus, comprising:

identifying derivation for an intra prediction mode of the chroma block;

determining an intra prediction mode of the chroma block based on a prediction mode derivation method in response to the derivation for the intra prediction mode of the chroma block; and

decoding the chroma block based on the intra prediction mode of the chroma block,

wherein the prediction mode derivation method includes:

obtaining a template predictor based on a reference pixel neighboring a pre-defined template;

determining a template prediction mode to minimize a difference between the pre-defined template and the template predictor; and

setting the template prediction mode as the intra prediction mode of the chroma block,

wherein the derivation for the intra prediction mode of the chroma block is identified based on at least one of a chroma mode derivation flag, a luma mode derivation flag, or division information of the chroma block, and

wherein the chroma mode derivation flag indicates derivation for the intra prediction mode of the chroma block, the luma mode derivation flag indicates derivation for an intra prediction mode of a luma block, and the division information comprises at least one of a division structure, shape or size of the chroma block,

wherein the method further comprising:

checking whether the division information of the chroma block is identical with division information of the luma block,

wherein the intra prediction mode of the chroma block is derived based on the division information of the chroma block that is identical with the division information of the luma block.

2. The method of claim 1 , further comprising:

obtaining the chroma mode derivation flag,

wherein the intra prediction mode of the chroma block is derived based on the chroma mode derivation flag.

3. The method of claim 1 , further comprising:

checking whether the intra prediction mode of the luma block has been derived based on the luma mode derivation flag,

wherein if the intra prediction mode of the luma block has been derived, the intra prediction mode of the chroma block is derived.

4. The method of claim 1 ,

wherein the chroma mode derivation flag or the luma mode derivation flag is defined in at least one level of a video parameter set, a sequence parameter set, a picture parameter set, a slice segment header, a coding unit header or a processing unit.

5. The method of claim 1 ,

wherein the pre-defined template neighbors a top or left of the chroma block and has an N×L or L×N size, and

wherein a maximum size of the reference pixel is 2(L+N)+1 neighboring the pre-defined template.

6. An apparatus for decoding a chroma block of a video signal, comprising:

one or more processors configured to:

identify derivation for an intra prediction mode of the chroma block, determine an intra prediction mode of the chroma block based on a prediction mode derivation method in response to the derivation for the intra prediction mode of the chroma block, obtain a predictor of the chroma block based on the intra prediction mode of the chroma block;

reconstruct the video signal based on the predictor of the chroma block,

obtain a template predictor based on a reference pixel neighboring a pre-defined template,

determine a template prediction mode to minimize a difference between the pre-defined template and the template predictor, and

set the template prediction mode as the intra prediction mode of the chroma block,

wherein the derivation for the intra prediction mode of the chroma block is identified based on at least one of a chroma mode derivation flag, a luma mode derivation flag, or division information of the chroma block, and

wherein the chroma mode derivation flag indicates derivation for the intra prediction mode of the chroma block, the luma mode derivation flag indicates derivation for an intra prediction mode of a luma block, and the division information comprises at least one of a division structure, shape or size of the chroma block,

wherein the one or more processors are further configured to:

check whether the division information of the chroma block is identical with division information of the luma block,

wherein the intra prediction mode of the chroma block is derived based on the division information of the chroma block that is identical with the division information of the luma block.

7. The apparatus of claim 6 , wherein the one or more processors are further configured to:

obtain the chroma mode derivation flag, and

wherein the intra prediction mode of the chroma block is derived based on the chroma mode derivation flag.

8. The apparatus of claim 6 , wherein the one or more processors are further configured to:

confirm whether the intra prediction mode of the luma block has been derived based on the luma mode derivation flag, and

wherein if the intra prediction mode of the luma block has been derived, the intra prediction mode of the chroma block is derived.

9. The apparatus of claim 6 ,

wherein the chroma mode derivation flag or the luma mode derivation flag is defined in at least one level of a video parameter set, a sequence parameter set, a picture parameter set, a slice segment header, a coding unit header or a processing unit.

10. The apparatus of claim 6 ,

wherein the pre-defined template neighbors a top or left of the chroma block and has an N×L or L×N size, and

wherein a maximum size of the reference pixel is 2(L+N)+1 neighboring the pre-defined template.