Quantization effect reduction method in low bit rate moving picture coding

Abstract

The reconstructed images from highly compressed MPEG and H.263 data have noticeable image degradations, such as blocking artifacts near the block boundaries, corner outliers at corner points of blocks and ringing noise near image edges, because the MPEG and H.263 quantize the transformed coefficients of 8x8 pixel blocks. A post-filtering algorithm is proposed to reduce quantization effects, such as blocking artifacts, corner outliers and ringing noise, in MPEG and H.263-decompressed images. The proposed post-filtering algorithm reduces the quantization effects adaptively by using both spatial frequency and temporal information extracted from the compressed data. The blocking artifacts are reduced by one-dimensional (1-D) horizontal or vertical low-pass filtering (LPF), and the ringing noise is reduced by two-dimensional (2-D) signal-adaptive filtering (SAF). A comparison study of the peak signal to noise ratio (PSNR) and the computation complexity analysis between the proposed post-filtering algorithm and the MPEG-4 VM (Verification Model) post-filtering algorithm are performed for several image sequences by computer simulation. According to the comparison study of PSNR and computation complexity analysis, the proposed algorithm shows better performance than the VM post-filtering algorithm, whereas the subjective image qualities of both algorithms are similar. A loop-filtering algorithm is also proposed to reduce the quantization effects adaptively by using both DCT domain analysis and temporal information. A comparison study of the PSNR, computation complexity analysis and the subjective quality evaluation between the proposed post-filtering algorithm and the proposed loop-filtering algorithm is also performed for several image sequences by computer simulation. According to the comparison study of PSNR and computation complexity analysis, the proposed post filtering shows slightly better performance than the proposed loop filtering in term of PSNR. However, t...