1. A method of coding video data, the method comprising: determining, for a block of video data, a set of most probable intra-prediction modes for predicting the block of video data, wherein the set of most probable intra-prediction modes has a size that is equal to a predetermined number that is greater than or equal to two; coding a value representative of an actual intra-prediction mode for the block based at least in part on whether or not the actual intra-prediction mode is included in the set of most probable intra-prediction modes; and coding the block using the actual intra-prediction mode, wherein determining the set of most probable intra-prediction modes comprises: determining a first intra-prediction mode for a left-neighboring block of the block; determining a second intra-prediction mode for an above-neighboring block of the block; when the first intra-prediction mode is different than the second intra-prediction mode, including both the first intra-prediction mode and the second intra-prediction mode in the set of most probable intra-prediction modes; when the first intra-prediction mode is the same as the second intra-prediction mode, and when the first and second intra-prediction modes comprise a mode other than a planar mode, including the first intra-prediction mode and the planar mode in the set of most probable intra-prediction modes; and, when the first intra-prediction mode is the same as the second intra-prediction mode, and when the first and second intra-prediction modes comprise a planar mode, including the planar mode and a DC mode in the set of most probable intra-prediction modes.

2. The method of claim 1, wherein the block comprises a luminance block, the method further comprising: determining, for a chrominance block corresponding to the luminance block, a mapping of a set of values to a set of intra-prediction modes, the set of intra-prediction modes comprising horizontal mode, vertical mode, planar mode, DC mode, and luma signal prediction mode, wherein when the actual intra-prediction mode for the luminance block comprises a mode other than horizontal mode, vertical mode, planar mode, and DC mode, the set of intra-prediction modes further comprises a reuse of luma intra-prediction mode mapped 50 229415/2 from a first value of the set of values, and wherein when the actual intra-prediction mode for the luminance block comprises one of horizontal mode, vertical mode, planar mode, and DC mode, the set of intra-prediction modes further comprises a mode other than horizontal mode, vertical mode, planar mode, and DC mode mapped from the first value of the set of values; coding a value representative of an actual intra-prediction mode for the chrominance block based on the mapping of the set of values to the set of modes; and coding the chrominance block using the actual intra-prediction mode for the chrominance block.

3. The method of claim 1, wherein the size of the set of most probable intra-prediction modes is equal to three, the method further comprising: determining a prediction direction of the first intra-prediction mode; comparing the prediction direction of the first intra-prediction mode to prediction directions of one or more other available intra-prediction modes; and including a third intra-prediction mode of the one or more available intra-prediction modes in the set of most probable intra-prediction modes, wherein the third intra-prediction mode has a prediction direction determined to be closest to the prediction direction of the first intra-prediction mode based on the comparison.

4. The method of claim 1, wherein: the size of the set of most probable intra-prediction modes is equal to four.

5. The method of claim 1, further comprising: selecting the actual intra-prediction mode, and wherein coding the block further comprises encoding the block based on the actual intra-prediction mode.

6. The method of claim 1, wherein: coding the block further comprises decoding the block using the actual intra prediction mode, and coding the value representative of the actual intra-prediction mode comprises determining the actual intra-prediction mode from the value. 51 229415/2

7. The method of claim 1, wherein when the actual intra-prediction mode is the planar, vertical, horizontal, or DC mode, a chroma intra-prediction mode is an upper-right direction intra-prediction mode.

8. A computer program product comprising a computer-readable storage medium having stored thereon instructions that, when executed, cause a processor of a video coding device to perform the method according to any one of the preceding claims.

9. A device for video coding, comprising: means for determining, for a block of video data a set of most probable intra prediction modes for predicting the block of video data, wherein the set of most probable intra-prediction modes has a size that is equal to a predetermined number that is greater than or equal to two; means for coding a value representative of an actual intra-prediction mode for the block based at least in part on whether or not the actual intra-prediction mode is included in the set of most probable intra-prediction modes; means for coding the block using the actual intra-prediction mode; means for determining a first intra-prediction mode for a left-neighboring block of the block; and, means for determining a second intra-prediction mode for an above-neighboring block of the block, wherein: when the first intra-prediction mode is different than the second intra prediction mode, means for including both the first intra-prediction mode and the second intra-prediction mode in the set of most probable intra-prediction modes; when the first intra-prediction mode is the same as the second intra-prediction mode, and when the first and second intra-prediction modes comprise a mode other than a planar mode, means for including the first intra-prediction mode and the planar mode in the set of most probable intra-prediction modes; and when the first intra-prediction mode is the same as the second intra-prediction mode, and when the first and second intra-prediction modes comprise a planar mode, means for including the planar mode and a DC mode in the set of most probable intra-prediction modes. 52 229415/210. The device of claim 9, wherein the block comprises a luminance block, the apparatus further comprising: means for determining, for a chrominance block corresponding to the luminance block, a mapping of a set of values to a set of intra-prediction modes, the set of intra prediction modes comprising horizontal mode, vertical mode, planar mode, DC mode, and luma signal prediction mode, wherein when the actual intra-prediction mode for the luminance block comprises a mode other than horizontal mode, vertical mode, planar mode, and DC mode, the set of intra-prediction modes further comprises a reuse of luma intra prediction mode mapped from a first value of the set of values, and wherein when the actual intra-prediction mode for the luminance block comprises one of horizontal mode, vertical mode, planar mode, and DC mode, the set of intra-prediction modes further comprises a mode other than horizontal mode, vertical mode, planar mode, and DC mode mapped from the first value of the set of values; means for coding a value representative of an actual intra-prediction mode for the chrominance block based on the mapping of the set of values to the set of modes; and means for coding the chrominance block using the actual intra-prediction mode for the chrominance block

11. The device of claim 9, wherein the size of the set of most probable intra-prediction modes is equal to three, the device further comprising: means for determining a prediction direction of a first intra-prediction mode; means for comparing the prediction direction of the first intra-prediction mode to prediction directions of one or more other available intra-prediction modes; means for including a third intra-prediction mode of the one or more available intra prediction modes in the set of most probable intra-prediction modes, wherein the third intra prediction mode has a prediction direction determined to be closest to the prediction direction of the first intra-prediction mode based on the comparison.12. The device of claim 9, wherein: the size of the set of most probable intra-prediction modes is equal to four.13. The device of claim 9, wherein the apparatus comprises a video encoder.']