Apparatus of decoding video data

An apparatus for generating a residual block, comprising:

• an entropy decoding unit configured to decode residual signals to generate quantized coefficient components;
• an inverse scanning unit configured to determine an inverse scan pattern and generate a quantized block using the inverse scan pattern;
• an inverse quantization unit configured to derive a quantization parameter and inversely quantize the quantized block using the quantization parameter to generate a transformed block;
• and
• an inverse transform unit configured to inversely transform the transformed block to generate a residual block,
• wherein when the quantization parameter is a chroma quantization parameter, the chroma quantization parameter is generated using a luma quantization parameter and an offset parameter indicating a relationship between the luma quantization parameter and the chroma quantization parameter,
• the luma quantization parameter is derived using a differential quantization parameter and a quantization parameter predictor, the differential quantization parameter is generated by entropy decoding,
• 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 a predetermined order, and
• if only one quantization parameter is available, the available quantization parameter is set as the quantization parameter predictor.