Method of removing deblocking artifacts
Provided is a method determines a boundary strength for each 4-sample edge lying on 8×8 sample grid, determines whether deblocking filtering is performed on the 4-sample edge or not if the boundary strength is not equal to zero, selects a deblocking filter if the deblocking filtering is performed on the 4-sample edge, and filters the 4-sample edge using the selected filter. Accordingly, the computational complexity required to determine the boundary strength according to the present invention is reduced by 50% or more when compared with the HEVC under development. Also, the memory capacity and bandwidth required to determine the boundary strength are reduced by 50% or more without deterioration of image quality.
1. A method for decoding image data, the method comprising:
generating a prediction block based on a prediction mode;
generating a quantization block by inversely scanning quantization coefficient information;
generating a transform block by inversely quantizing the quantization block using a quantization parameter;
generating a residual block by inversely transforming the transform block;
generating a reconstructed picture by using the prediction block and the residual block; and
applying a deblocking filter on the reconstructed picture,
wherein the deblocking filtering is applied between two adjacent blocks P and Q containing samples p0 and q0 respectively by using a boundary quantization parameter when a boundary strength is not zero,
wherein the boundary quantization parameter is set to an average value of a quantization parameter of block P and a quantization parameter of block Q, and the quantization parameter is derived by adding a residual quantization parameter and a quantization parameter predictor, and
wherein the quantization parameter predictor is an average of two available quantization parameters among a left quantization parameter, an above quantization parameter, and a previous quantization parameter.
2. The method of claim 1 , wherein the average of the two available quantization parameters is rounded off.
3. The method of claim 1 , wherein when at least two of the left quantization parameter, the above quantization parameter and the previous quantization parameter are available, an average of two available quantization parameters selected in a predetermined order is set as the quantization parameter predictor.
4. The method of claim 3 , wherein the predetermined order is the order of the left quantization parameter, the above quantization parameter and the previous quantization parameter.
5. The method of claim 1 , wherein the previous quantization parameter is set as the quantization parameter predictor when both of the left quantization parameter and the above quantization parameter are unavailable.
6. The method of claim 1 , wherein the deblocking filter to be applied is selected by using the boundary quantization parameter.
7. The method of claim 1 , wherein the quantization parameter predictor is derived per quantization unit which includes at least one coding unit.
8. The method of claim 1 , wherein the transform block is inversely transformed by using transform matrix determined according to a size of a transform unit.