Method of constructing merge list

1. An image encoding apparatus comprising:

an inter prediction module for determining motion information of a current block, and generating a prediction block of the current block using the motion information;

a transform module for transforming a residual block to generate a transformed block;

a quantization module for quantizing the transformed block using a quantization parameter and a quantization matrix to generate a quantized block;

a scanning module for scanning coefficient components of the quantized block using a diagonal scan; and

an entropy coding module for entropy-coding the scanned coefficient components of the quantized block;

wherein the motion information is encoded by performing the sub-steps of:

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

selecting a merge predictor among merge candidates of the merge list; and

encoding a merge index specifying the merge predictor,

wherein if the current block is a second prediction unit partitioned by asymmetric partitioning, the spatial merge candidate corresponding to a first prediction unit partitioned by the asymmetric partitioning is set as unavailable, and information of an above-left block is allowed to set as one of the merge candidates,

wherein a reference picture index of the temporal merge candidate is set as 0, and 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 an LCU,

wherein the quantization parameter is determined per a quantization unit and is encoded using a quantization parameter predictor, and the quantization parameter predictor is generated by averaging two quantization parameters of a left quantization parameter, an above quantization parameter and a previous quantization parameter if two or more quantization parameters are available among the left quantization parameter, the above quantization parameter and the previous quantization parameter, and

wherein if only one of the left quantization parameter and the above quantization parameter is available, an average of the available quantization parameter and the previous quantization parameter is set as the quantization parameter predictor.

2. The apparatus of claim 1 , wherein if the size of the current block is (3/2)N×2N, the left spatial merge candidate is set as unavailable.

3. The apparatus of claim 2 , wherein the left spatial merge candidate is motion information of the left prediction unit of the current block.

4. The apparatus of claim 2 , wherein if an above spatial merge candidate has the same motion information of the left spatial merge candidate, the above spatial merge candidate is set as unavailable.

5. The apparatus of claim 2 , wherein the size of the current block is determined based on a partitioning mode and a size of the coding unit.

6. The apparatus of claim 1 , wherein if a current coding unit is a minimum coding unit, asymmetric partitioning is not allowed.