Method of deriving motion information

1. A method of decoding video data in a merge mode, the method comprising:

generating a quantized block by inverse-scanning quantized coefficient components;

generating a transformed block by inverse-quantizing the quantized block using a quantization parameter;

generating a residual block by inverse-transforming the transformed block;

constructing a merge list using available spatial and temporal merge candidates;

setting a merge candidate on the merge list specified by a merge index as motion information of a current prediction unit;

generating a prediction block of the current prediction unit using the motion information; and

generating a reconstructed block using the prediction block and the residual block,

wherein the inverse scan pattern is selected among a diagonal scan, a vertical scan and a horizontal scan, and when the size of the quantized block is larger than a predetermined size, a plurality of subsets are generated and the quantized block is generated by inversely scanning the plurality of subsets using the inverse scan pattern,

wherein the quantization parameter is derived per a quantization unit,

wherein a minimum size of the quantization unit is adjusted per picture,

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, and

wherein if only one quantization parameter 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.

2. The method of claim 1 , wherein a reference picture index and a motion vector of the current prediction unit are a reference picture index and a motion vector of a merge candidate specified by the merge index.

3. The method of claim 2 , wherein the reference picture index of the temporal merge candidate is set as 0.

4. The method of claim 1 , wherein a motion vector of the temporal merge candidate is a motion vector of a temporal merge candidate block within a temporal merge candidate picture, and a position of the temporal merge candidate block is determined depending on a position of the current block within a largest coding unit (LCU).

5. The method of claim 4 , wherein the motion vector of the temporal merge candidate is a motion vector of a motion vector storing unit corresponding to the position of the temporal merge candidate block.

6. The method of claim 5 , wherein a size of the motion vector storing unit is 16×16.

7. The method of claim 1 , wherein if multiple coding units belong to the quantization unit, the quantization parameter for a first coding unit of the multiple coding units is derived and used for the multiple coding units.

8. The method of claim 1 , wherein if an absolute value of the differential quantization parameter is zero, the bin indicating the sign of the differential quantization parameter does not exist.

9. The method of claim 1 , wherein the predetermined order is an order of the left quantization parameter, the above quantization parameter and the previous quantization parameter.

10. The method of claim 1 , wherein if the size of the transform unit is equal to or larger than 8×8, the quantized block is generated using a last non-zero coefficient position and non-zero subset flag.