A device configured to encode video data is discussed. The device includes a generator configured to generate a prediction block of a current prediction unit using a reference index and a motion vector of the current prediction unit, and a residual block using a difference between the current prediction unit and the prediction block; a transformer configured to transform the residual block to generate a transform block; a quantizer configured to quantize coefficients of the transform block to generate a quantization block using a quantization parameter. Further, the quantizer generates the quantization block by selecting two effective quantization parameters that are available and exist among left, upper, and previous quantization parameters according to an order of priority levels set for the left, upper, and previous quantization parameters and using an average of the two effective quantization parameters; and an entropy-coder configured to entropy-code the quantization block using a scan pattern.