1. A method of decoding video data in a merge mode, comprising: constructing a merge list using available spatial and temporal merge candidates; setting a merge candidate on the merge list corresponding to a merge index as motion information of a current prediction unit; generating a prediction block of the current prediction unit using the motion information; generating a quantized block by inverse-scanning quantized coefficient components, generating a transformed block by inverse-quantizing the quantized block using a quantization parameter, and generating a residual block by inverse-transforming the transformed block, wherein when the current prediction unit is a second prediction unit partitioned by asymmetric partitioning, a spatial merge candidate corresponding to a first prediction unit partitioned by the asymmetric partitioning is excluded from the merge list, and a motion vector of the temporal merge candidate is determined depending on a position of a current block within a largest coding unit (LCU), wherein the quantization parameter is generated per quantization unit, and a minimum size of the quantization unit is adjusted by a picture parameter set, wherein the quantization parameter is generated using a differential quantization parameter and a quantization parameter predictor, wherein if two or more quantization parameters are available among a left quantization parameter, an above quantization parameter and a previous quantization parameter of a current coding unit, the quantization parameter predictor is generated using two available quantization parameters determined according to a predetermined order, wherein if only one is available among the left quantization parameter, the above quantization parameter and the previous quantization parameter of the current coding unit, the available quantization parameter is set as the quantization parameter predictor, and wherein the differential quantization parameter is restored using a bin string indicating an absolute value of the differential quantization parameter and a bin indicating a sign of the differential quantization parameter.