Method and system for intracoding in video encoding

1. A method of intra-coding blocks of pixels in a digital video sequence, the method comprising:

selecting a block transform of a plurality of block transforms according to a spatial prediction mode used in generating a block of pixel residual values from a block of pixels, wherein the block transform is based on a single directional transform matrix predetermined for the spatial prediction mode and is a same size as the block of pixel values, wherein the single directional transform matrix for carrying out a directional transform;

applying the block transform to the block of pixel residual values to generate transform coefficients of the residual pixel values, wherein applying the block transform comprises computing a product of a sparse matrix, a DCT matrix, the block of pixel residual values, a transpose of the DCT matrix, and a transpose of the sparse matrix, wherein the sparse matrix is derived from the single directional transform matrix; and

entropy coding the generated transform coefficients.

2. The method of claim 1 , wherein applying the block transform further comprises:

computing a product of the directional transform matrix, the block of pixel residual values, and a transpose of the directional transform matrix to generate the transform coefficients.

3. The method of claim 2 , wherein each of the plurality of block transforms is associated with at least one spatial prediction mode, and each of the plurality of block transforms is a single directional transform matrix predetermined for the at least one associated spatial prediction mode.

4. The method of claim 1 , further comprising:

selecting the block transform according to another spatial prediction mode used in generating another block of pixel residual values from another block of pixels; and

applying the block transform to the another block of pixel residual values.

5. The method of claim 1 , wherein the sparse matrix is one selected from a group consisting of a diagonal matrix and a rotational matrix.

6. The method of claim 1 , wherein each of the plurality of block transforms is associated with at least one spatial prediction mode, and each of the plurality of block transforms is a predetermined sparse matrix derived from a single directional transform matrix predetermined for the at least one associated spatial prediction mode.

7. A video encoder configured to intra-code blocks of pixels in a digital video sequence, the video encoder comprising:

a transform component configured to

select a block transform of a plurality of block transforms according to a spatial prediction mode used in generating a block of pixel residual values from a block of pixels, wherein the block transform is based on a single directional transform matrix predetermined for the spatial prediction mode and is a same size as the block of pixel values, wherein the single directional transform matrix for carrying out a directional transform; and

apply the block transform to the block of pixel residual values to generate transform coefficients of the residual pixel values, wherein applying the block transform comprises computing a product of a sparse matrix, a DCT matrix, the block of pixel residual values, a transpose of the DCT matrix, and a transpose of the sparse matrix, wherein the sparse matrix is derived from the single directional transform matrix; and

an entropy encoding component configured to entropy code the generated transform coefficients.

8. The video encoder of claim 7 , wherein the transform component is further configured to apply the block transform by computing a product of the single directional transform matrix, the block of pixel residual values, and a transpose of the single directional transform matrix to generate the transform coefficients.

9. The video encoder of claim 8 , wherein the transform component is further configured to store the plurality of block transforms, and wherein each of the plurality of block transforms is associated with at least one spatial prediction mode, and each of the plurality of block transforms is a single directional transform matrix predetermined for the at least one associated spatial prediction mode.

10. The video encoder of claim 8 , wherein the transform component is further configured to:

select the block transform according to another spatial prediction mode used in generating another block of pixel residual values from another block of pixels; and

apply the block transform to the another block of pixel residual values.

11. The video encoder of claim 7 , wherein the sparse matrix is one selected from a group consisting of a diagonal matrix and a rotational matrix.

12. The video encoder of claim 7 , wherein the transform component is further configured to store the plurality of block transforms, and wherein each of the plurality of block transforms is associated with at least one spatial prediction mode, and each of the plurality of block transforms is a predetermined sparse matrix derived from a single directional transform matrix predetermined for the at least one associated spatial prediction mode.

13. A digital system configured to intra-code blocks of pixels in a digital video sequence the digital system comprising:

means for selecting a block transform of a plurality of block transforms according to a spatial prediction mode used in generating a block of pixel residual values from a block of pixels, wherein the block transform is based on a single directional transform matrix predetermined for the spatial prediction mode and is a same size as the block of pixel values, wherein the single directional transform matrix for carrying out a directional transform;

means for applying the block transform to the block of pixel residual values to generate transform coefficients of the residual pixel values, wherein the means for applying the block transform comprises a means for computing a product of a sparse matrix, a DCT matrix, the block of pixel residual values, a transpose of the DCT matrix, and a transpose of the sparse matrix, wherein the sparse matrix is derived from the single directional transform matrix; and

means for entropy coding the generated transform coefficients.

14. The digital system of claim 13 , wherein the means for applying the block transform comprises:

means for computing a product of the single directional transform matrix, the block of pixel residual values, and a transpose of the single directional transform matrix to generate the transform coefficients.

15. The digital system of claim 14 , wherein each of the plurality of block transforms is associated with at least one spatial prediction mode, and each of the plurality of block transforms is a single directional transform matrix predetermined for the at least one associated spatial prediction mode.

16. The digital system of claim 13 , further comprising:

means for selecting the block transform according to another spatial prediction mode used in generating another block of pixel residual values from another block of pixels; and

means for applying the block transform to the another block of pixel residual values.

17. The digital system of claim 13 , wherein each of the plurality of block transforms is associated with at least one spatial prediction mode, and each of the plurality of block transforms is a predetermined sparse matrix derived from a single directional transform matrix predetermined for the at least one associated spatial prediction mode.