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 processing a video signal, the method comprising:
receiving, with a decoding apparatus, the video signal;
determining, with the decoding apparatus, a candidate mode list based on intra prediction mode information of neighboring blocks adjacent to a current block, the candidate mode list including at least three candidate prediction modes;
parsing, with the decoding apparatus, a mode indication flag of the current block from the video signal, the mode indication flag indicating whether an intra prediction mode of the current block is directly determined from a most probable mode;
when the mode indication flag indicates that the intra prediction mode of the current block is not directly determined from the most probable mode:
parsing, with the decoding apparatus, first intra prediction mode information of the current block from the video signal;
reordering, with 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;
obtaining, with the decoding apparatus, second intra prediction mode information of the current block from the first intra prediction mode information based on the at least three reordered candidate prediction modes; and
decoding, with the decoding apparatus, the current block using the second intra prediction mode information,
wherein obtaining the second intra prediction mode information comprises:
comparing the first intra prediction mode information with one of the at least three reordered candidate prediction modes, and
increasing a value of the first intra prediction mode information by one when the first intra prediction mode information is greater than or equal to the one of the at least three reordered candidate prediction modes.
2. The method of claim 1 , wherein the neighboring blocks include an upper block and a left block adjacent to the current block.
3. The method of claim 2 , wherein the most probable mode is one of the intra prediction mode information of the upper block and the intra prediction mode information of the left block.
4. The method of claim 1 , wherein the most probable mode is the intra prediction mode information with a lowest index of the neighboring blocks.
5. The method of claim 1 , wherein the most probable mode is a median value of the intra prediction mode information of the neighboring blocks.
6. An apparatus for processing a video signal, the apparatus comprising:
an entropy decoding unit configured to:
parse a mode indication flag of a current block from a video signal, the mode indication flag indicating whether an intra prediction mode of the current block is directly determined from a most probable mode, and
parse first intra prediction mode information of the current block from the video signal when the mode indication flag indicates that the intra prediction mode of the current block is not directly determined from the most probable mode; and
an intra predicting unit configured to:
determine a candidate mode list based on intra prediction mode information of neighboring blocks adjacent to the current block, the candidate mode list including at least three candidate prediction modes,
when the mode indication flag indicates that the intra prediction mode of the current block is not directly determined from the most probable mode:
reorder the at least three candidate prediction modes such that a lower index is assigned to a candidate prediction mode having a lower value, and
obtain second intra prediction mode information of the current block from the first intra prediction mode information based on the at least three reordered candidate prediction modes, and
decode the current block using the second intra prediction mode information,
wherein obtaining the second intra prediction mode information comprises:
comparing the first intra prediction mode information with one of the at least three candidate prediction modes, and
increasing a value of the first intra prediction mode information by one when the first intra prediction mode information is greater than or equal to the one of the at least three candidate prediction modes.
7. The apparatus of claim 6 , wherein the neighboring blocks include an upper block and a left block adjacent to the current block.
8. The apparatus of claim 7 , wherein the most probable mode is one of the intra prediction mode information of the upper block and the intra prediction mode information of the left block.
9. The apparatus of claim 6 , wherein the most probable mode is the intra prediction mode information with a lowest index of the neighboring blocks.
10. The apparatus of claim 6 , wherein the most probable mode is a median value of the intra prediction mode information of the neighboring blocks.