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 of removing blocking artifacts by a decoding apparatus, the method comprising:
determining, by the decoding apparatus, a boundary strength for only each of every 4-sample edge in a coding unit which lies on grid lines of an 8×8 sample grid and is an edge of a prediction unit or a transform unit;
determining, by the decoding apparatus, whether or not deblocking filtering is performed on the 4-sample edge if the boundary strength for the 4-sample edge is not equal to zero, wherein the boundary strength for the 4-sample edge is determined based on two blocks immediately adjacent to and located on either side of the 4-sample edge;
selecting, by the decoding apparatus, a deblocking filter to be applied among a strong filter and a weak filter if the deblocking filtering is performed on the 4-sample edge;
filtering, by the decoding apparatus, the 4-sample edge using the selected deblocking filter, and
wherein the boundary strength is set equal to 0, 1 or 2.
2. The method of claim 1 , wherein the boundary strength is set equal to zero if the 4-sample edge is not the edge of the transform unit and the 4-sample edge is not the edge of the prediction unit.
3. The method of claim 1 , wherein vertical 4-sample edges are filtered first and then horizontal 4-sample edges are filtered.
4. The method of claim 3 , wherein the boundary strength is set equal to 2 if a prediction unit containing the sample p0 or a prediction unit containing the sample q0 is intra-coded.
5. The method of claim 4 , wherein the boundary strength is set equal to 1 or 0 if a prediction unit containing the sample p0 and a prediction unit containing the sample q0 are inter-coded.
6. The method of claim 1 , wherein whether or not the deblocking filtering is to be performed on the 4-sample edge is determined using a boundary quantization parameter.
7. The method of claim 6 , wherein the boundary quantization parameter is an average of a quantization parameter of P block containing sample p0 and a quantization parameter of Q block containing sample q0.
8. The method of claim 7 , wherein the average is a value rounded off.
9. The method of claim 7 , wherein the deblocking filter is selected using a boundary quantization parameter.