Method for generating prediction block in amvp mode

Abstract

An apparatus for decoding video data and including an entropy decoder configured to separate at least an intra mode index, motion information, a quantization parameter and a quantized coefficient sequence from a coded bit stream by decoding the coded bit stream; an inverse quantizer/inverse transformer configured to convert the quantized coefficient sequence to a quantization block, inversely quantize coefficients of the quantization block using the quantization parameter to generate a transform block, and inversely transform the transform block to generate a residual block; an intra predictor configured to restore an intra prediction mode of a current prediction unit using the intra mode index and generate a prediction block of the current prediction unit according to the intra prediction mode when the coded bit stream is coded in the intra prediction mode; and a motion compensation predictor configured to generate a prediction block of a current prediction unit using a reference index and a motion vector derived from the motion information when the coded bit stream is coded in an inter prediction mode. Further, the motion vector is decoded using a motion vector predictor which is set equal to one of an effective spatial merge candidate and a temporal merge candidate, and a motion vector of the temporal merge candidate is a motion vector of a temporal merge candidate within a temporal merge candidate picture, and the quantization parameter is encoded using an average of two effective quantization parameters among a left quantization parameter, an upper quantization parameter and a previous quantization parameter of a current coding unit, When the quantized block is larger than a predetermined size, the quantized coefficient sequence is inversely scanned in a unit of sub-block using a scan pattern and a plurality of sub-blocks are inversely scanned using a scan pattern, and the scan pattern for inversely scanning the plurality of sub-blocks is the same as the scan pattern for inversely scanning the quantized coefficients sequence. Also, the scan pattern for inversely scanning the quantized coefficients is determined according to the intra prediction mode and a size of a transform unit when the coded bit stream is coded in the intra prediction mode.