Imaging decoding apparatus

An image decoding device comprising:

• a processor;
• and
• a non-transitory computer-readable medium having stored thereon instructions that, when executed, cause the processor to perform a method, the method comprising:
• reconstructing a prediction mode and creating a prediction block with the reconstructed prediction mode;
• converting residual signals into a two-dimensional quantization block;
• inversely quantizing the quantization block using a quantization parameter;
• and
• inversely-transforming the inversely-quantized block,
• wherein the quantization parameter is derived using a received residual quantization parameter and a quantization parameter predictor, and the quantization parameter predictor used for deriving the quantization parameter is created using a quantization parameter of a left coding unit of a current coding unit and a quantization parameter of a top coding unit of the current coding unit,
• wherein a size of the prediction block is determined based on transform size information,
• wherein the prediction mode is reconstructed using a first intra prediction mode group consisting of three intra prediction modes among 34 intra prediction modes, an intra prediction mode group indicator and a prediction mode index,
• wherein the three intra prediction modes of the first intra prediction mode group are determined using intra prediction modes of a left block and a top block of a current block,
• wherein the three intra prediction modes of the first intra prediction mode group are determined as a DC mode, a planar mode and a vertical mode among the 34 intra prediction modes when the intra prediction modes of the left block and the top block are not unavailable,
• wherein the prediction mode is set as an intra prediction mode indicated by the prediction mode index in the first intra prediction mode group when the intra prediction mode group indicator indicates the first intra prediction mode group, and
• wherein the prediction mode is set as an intra prediction mode indicated by the prediction mode index in a second intra prediction mode group consisting of 31 intra prediction modes besides the three intra prediction modes of the first intra prediction mode group when the intra prediction mode group indicator indicates the second intra prediction mode group.