Method for restoring an intra prediction mode
Provided is a method that de-multiplexes a bit stream to extract intra prediction mode information and residual signals, restores an intra prediction mode of a current prediction unit using the intra prediction information and intra prediction modes of prediction units adjacent to the current prediction unit, generates reference pixels using one or more available reference pixel if there exist unavailable reference pixels of the prediction unit, adaptively filters the reference pixels based on the restored intra prediction mode, generates a prediction block using the restored intra prediction mode and the reference pixels, decodes the residual signal to generating a residual block, and generates a reconstructed block using the prediction block and the residual block. Accordingly, additional bits resulted from increase of a number of intra prediction mode are effectively reduced. Also, an image compression ratio can be improved by generating a prediction block similar to an original block.
1. A method for restoring an intra prediction mode, comprising:
restoring an intra prediction mode group indicator and a prediction mode index of a current prediction unit;
generating an intra prediction mode group using available intra prediction modes of a left prediction unit and an above prediction unit neighboring the current prediction unit, wherein the number of intra prediction modes belonging to the intra prediction mode group is fixed to three; and
determining an intra prediction mode which is included in the intra prediction mode group and indicated by the intra prediction mode index as the intra prediction mode of the current prediction unit when the intra prediction mode group indicator indicates that the intra prediction mode of the current prediction unit belongs to the intra prediction mode group,
wherein, when only one intra prediction mode out of the intra prediction modes of the left prediction unit and the above prediction unit is available, the intra prediction mode group includes the one available intra prediction mode of the respective prediction units and two additional intra prediction modes that are determined such that when the one available intra prediction mode is a non-directional intra prediction mode, the two additional intra prediction modes include another non-directional intra prediction mode and a vertical mode.
2. The method of claim 1 , wherein, when the one available intra prediction mode is a DC mode, the two additional intra prediction modes include a planar mode and the vertical mode.
3. The method of claim 1 , wherein, when the one available intra prediction mode is a planar mode, the two additional intra prediction modes include a DC mode and the vertical mode.