Enhanced intra prediction mode signaling
A method and apparatus for signaling and receiving a video signal for processing is disclosed. Methods for determining a most probable mode for predicting a current prediction block are provided as well as new methods for grouping intra prediction modes into prediction groups. Methods for predicting a prediction block of video data as well as signaling intra prediction modes are also provided.
1. A method for decoding a video signal by a decoding apparatus, the method comprising:
determining, by the decoding apparatus, an intra prediction mode of a current block, wherein determining the intra prediction mode of the current block comprises:
determining, by the decoding apparatus, a candidate mode list based on intra prediction modes of neighboring blocks adjacent to the current block, the candidate mode list comprising at least three candidate prediction modes;
obtaining, by the decoding apparatus from the video signal, flag information indicating whether the intra prediction mode of the current block is derived from a neighboring block; and
when the flag information indicates that the intra prediction mode of the current block is not derived from a neighboring block:
obtaining, by the decoding apparatus, intra prediction mode information of the current block from the video signal;
reordering, by the decoding apparatus, the at least three candidate prediction modes such that a lower index is assigned to a candidate prediction mode having a lower value; and
obtaining, by the decoding apparatus, the intra prediction mode of the current block based on the intra prediction mode information and the at least three reordered candidate prediction modes; and
obtaining, by the decoding apparatus, predicted samples for the current block based on the determined intra prediction mode.
2. The method of claim 1 , wherein obtaining the intra prediction mode of the current block comprises:
comparing the intra prediction mode information with one of the at least three reordered candidate prediction modes; and
assigning a value of the intra prediction mode information plus one to the intra prediction mode of the current block when the intra prediction mode information is greater than or equal to the one of the at least three reordered candidate prediction modes.
3. The method of claim 1 , wherein the neighboring blocks comprise an upper neighboring block and a left neighboring block adjacent to the current block.
4. The method of claim 1 , wherein an intra prediction mode is one of an intra angular prediction mode, an intra planar prediction mode, or an intra DC prediction mode.
5. The method of claim 1 , wherein an intra prediction mode has one value of 0 to 33.
6. The method of claim 1 , further comprising:
obtaining transform coefficient information from the video signal;
obtaining residual data by performing an inverse-transform operation based on the obtained transform coefficient information; and
reconstructing the current block based on the residual data and the predicted current block.
7. An apparatus configured to decode a video signal, the apparatus comprising:
an intra predicting unit configured to:
determine an intra prediction mode of a current block, and
obtain predicted samples for the current block based on the determined intra prediction mode,
wherein determining the intra prediction mode of the current block comprises:
determining a candidate mode list based on intra prediction modes of neighboring blocks adjacent to the current block, the candidate mode list including at least three candidate prediction modes;
obtaining flag information indicating whether the intra prediction mode of the current block is derived from a neighboring block;
when the flag information indicates that the intra prediction mode of the current block is not derived from a neighboring block:
obtaining intra prediction mode information of the current block,
reordering the at least three candidate prediction modes such that a lower index is assigned to a candidate prediction mode having a lower value, and
obtaining the intra prediction mode of the current block based on the intra prediction mode information and the at least three reordered candidate prediction modes.
8. The apparatus of claim 7 , wherein obtaining the intra prediction mode of the current block comprises:
comparing the intra prediction mode information with one of the at least three reordered candidate prediction modes; and
assigning a value of the intra prediction mode information plus one to the intra prediction mode of the current block when the intra prediction mode information is greater than or equal to the one of the at least three reordered candidate prediction modes.
9. The apparatus of claim 7 , wherein the neighboring blocks comprise an upper neighboring block and a left neighboring block adjacent to the current block.
10. The apparatus of claim 7 , wherein an intra prediction mode is one of an intra angular prediction mode, an intra planar prediction mode, or an intra DC prediction mode.
11. The apparatus of claim 7 , wherein an intra prediction mode has one value of 0 to 33.
12. The apparatus of claim 7 , further comprising:
an entropy decoding unit configured to obtain transform coefficient information from the video signal; and
an inverse transform unit configured to obtain residual data by performing an inverse-transform operation based on the obtained transform coefficient information, and reconstruct the current block based on the residual data and the predicted current block.