Reconstructed block creating method

1. A reconstructed block creating method in a decoder, the method comprising:

obtaining an intra prediction mode group indicator and a prediction mode index from a received bitstream;

decoding an intra prediction mode using the intra prediction mode group indicator, the prediction mode index and a most probable mode (MPM) group, wherein the MPM group is generated using intra prediction modes of left and top blocks of a current block, and the MPM group includes three intra prediction modes;

constructing a prediction block using the intra prediction mode and reference pixels;

inversely quantizing a received residual signal using a quantization parameter to create a quantized block and inversely transforming the quantized block to create a residual block; and

adding the prediction block and the residual block to create a reconstructed block,

wherein the quantization parameter is reconstructed using received information indicating a minimum quantization coding unit (CU) size and the information indicating the minimum quantization CU size is determined by a parameter transmitted from a picture parameter set, and

wherein an intra prediction mode of the current block is determined as an intra prediction mode indicated by the prediction mode index in the MPM group when the intra prediction mode group indicator indicates the MPM group, and the intra prediction mode of the current block is determined out of intra prediction modes other than the three intra prediction modes in the MPM mode group using the three intra prediction modes in the MPM mode group and the prediction mode index when the intra prediction mode group indicator does not indicate the MPM group,

wherein when the intra prediction modes of the left and top blocks are not equal to each other and non-directional intra prediction modes, the MPM group includes the intra prediction modes of the left and top blocks and a vertical mode.

2. The reconstructed block creating method according to claim 1 , wherein when the intra prediction modes of the left and top blocks are not equal to each other and directional intra prediction modes, the MPM group includes the intra prediction modes of the left and top blocks and a planar mode.

3. The reconstructed block creating method according to claim 1 , wherein the non-directional intra prediction mode are a planar mode and a DC mode, and the mode number 0 is assigned to the planar mode.

4. The reconstructed block creating method according to claim 1 , whether a method of entropy-encoding the prediction mode index varies depending whether the intra prediction mode belongs to the MPM group or not.

5. A bit stream stored on a computer-readable medium comprising a program code for performing, when executed on a computer, a method according to claim 1 .

6. A prediction information encoding method in an encoder, the method comprising:

generating a prediction block with reference pixels and a selected intra prediction mode;

generating a residual block with an original block and the prediction block;

transforming and quantizing the residual block to generate quantized coefficients;

generating an intra prediction mode indicator and a prediction mode index;

entropy-encoding the intra prediction mode indicator, the prediction mode index and the quantized coefficients; and

signaling a bit stream comprising the encoded intra prediction mode indicator, the encoded prediction mode index and the encoded quantized coefficients,

wherein the intra prediction mode indicator indicates whether or not the selected intra prediction mode included in a most probable mode (MPM) group,

wherein the MPM group is constructed using intra prediction modes of left and top blocks of a current block and the MPM group includes three intra prediction modes;

wherein the prediction mode index indicates the selected intra prediction mode among the three intra prediction modes in the MPM group when the intra prediction mode indicator indicates that the selected intra prediction mode is included in the MPM group, and the prediction mode index indicates the selected intra prediction mode among intra prediction modes besides the three intra prediction modes in the MPM group when the intra prediction mode indicator does not indicate that the selected intra prediction mode is included in the MPM group, and

wherein when the intra prediction modes of the left and top blocks are not equal to each other and non-directional intra prediction modes, the MPM group includes the intra prediction modes of the left and top blocks and a vertical mode.

7. The prediction information encoding method according to claim 6 , wherein when the intra prediction modes of the left and top blocks are not equal to each other and directional intra prediction modes, the MPM group includes the intra prediction modes of the left and top blocks and a planar mode.

8. The prediction information encoding method according to claim 6 , wherein the non-directional intra prediction mode are a planar mode and a DC mode, and the mode number 0 is assigned to the planar mode.

9. The prediction information encoding method according to claim 6 , whether a method of entropy-encoding the prediction mode index varies depending whether or not the selected intra prediction mode belongs to the MPM group.

10. A non-transitory computer-readable storage medium storing encoded video information, comprising:

a bit stream stored in the medium, the bit stream comprising entropy-encoded information on an intra prediction mode indicator, a prediction mode index and a quantized coefficients,

wherein the quantized coefficients is generated by transforming and quantizing a residual block generated with an original block and a prediction block, and the prediction block is generated using reference pixels and a selected intra prediction mode,

wherein the intra prediction mode indicator indicates whether or not the selected intra prediction mode included in a most probable mode (MPM) group which is constructed using intra prediction modes of left and top blocks of a current block and the MPM group, constructed using intra prediction modes of left and top blocks of a current block, includes three intra prediction modes,

wherein the prediction mode index indicates the selected intra prediction mode among the three intra prediction modes in the MPM group when the intra prediction mode indicator indicates that the selected intra prediction mode is included in the MPM group, and the prediction mode index indicates the selected intra prediction mode among intra prediction modes besides the three intra prediction modes in the MPM group when the intra prediction mode indicator does not indicate that the selected intra prediction mode is included in the MPM group, and

wherein when the intra prediction modes of the left and top blocks are not equal to each other and non-directional intra prediction modes, the MPM group includes the intra prediction modes of the left and top blocks and a vertical mode.