TY - JOUR
T1 - On the POCS-based postprocessing technique to reduce the blocking artifacts in transform coded images
AU - Paek, Hoon
AU - Kim, Rin Chul
AU - Lee, Sang Uk
PY - 1998
Y1 - 1998
N2 - In this paper, we propose a novel postprocessing technique, based on the theory of projections onto convex sets (POCS), to reduce the blocking artifacts in transform-coded images. It is assumed, in our approach, that the original image is highly correlated. Thus, the global frequency characteristics in two adjacent blocks are similar to the local ones in each block. We consider the high-frequency components in the global characteristics of a decoded image, which are not found in the local ones, as the results from the blocking artifact. We employ N-point discrete cosine transform (DCT) to obtain the local characteristics, and 2N-point DCT to obtain the global ones, and then derive the relation between N-point and 2N-point DCT coefficients. A careful comparison of N-point with 2N-point DCT coefficients makes it possible to detect the undesired high-frequency components, mainly caused by the blocking artifact. Then, we propose novel convex sets and their projection operators in the DCT domain. The performances of the proposed and conventional techniques are compared on the still images, decoded by JPEG. The results show that, regardless of the content of the input images, the proposed technique yields significantly better performance than the conventional techniques in terms of objective quality, subjective quality, and convergence behavior.
AB - In this paper, we propose a novel postprocessing technique, based on the theory of projections onto convex sets (POCS), to reduce the blocking artifacts in transform-coded images. It is assumed, in our approach, that the original image is highly correlated. Thus, the global frequency characteristics in two adjacent blocks are similar to the local ones in each block. We consider the high-frequency components in the global characteristics of a decoded image, which are not found in the local ones, as the results from the blocking artifact. We employ N-point discrete cosine transform (DCT) to obtain the local characteristics, and 2N-point DCT to obtain the global ones, and then derive the relation between N-point and 2N-point DCT coefficients. A careful comparison of N-point with 2N-point DCT coefficients makes it possible to detect the undesired high-frequency components, mainly caused by the blocking artifact. Then, we propose novel convex sets and their projection operators in the DCT domain. The performances of the proposed and conventional techniques are compared on the still images, decoded by JPEG. The results show that, regardless of the content of the input images, the proposed technique yields significantly better performance than the conventional techniques in terms of objective quality, subjective quality, and convergence behavior.
KW - Blocking artifact
KW - DCT
KW - POCS
KW - Postprocessing
UR - http://www.scopus.com/inward/record.url?scp=0032096065&partnerID=8YFLogxK
U2 - 10.1109/76.678636
DO - 10.1109/76.678636
M3 - Article
AN - SCOPUS:0032096065
SN - 1051-8215
VL - 8
SP - 358
EP - 367
JO - IEEE Transactions on Circuits and Systems for Video Technology
JF - IEEE Transactions on Circuits and Systems for Video Technology
IS - 3
ER -