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Blocking artifact is a major limitation of DCT-based codec at low bit rates. This degradation is likely to influence the judgment of a final user. This work presents a powerful post-processing filter in the DCT frequency domain. The proposed algorithm adopts a shift block within four adjacent DCT blocks to reduce computational complexity. The artifacts resulting from quantized and de-quantized process are eliminated by slightly modifying several DCT coefficients in the shift block. Simulation results indicate that the proposed method produces the best image quality in terms of both objective and subjective metrics.

The blocking effect is a major drawback of the DCT-based compression scheme at low bit rates. Significantly decreasing blocking effects can raise compression ratios for a particular image quality, or improve the quality with regard to the specific bit rate of compression. This work presents a scheme based on two mode filters in terms of the activity across block boundaries. For smooth regions, the strong smooth filter exploits the correlation between the neighboring blocks to reduce the discontinuity of the pixels across the boundaries. The weak smooth filter employs an edge-preserving smooth filter for texture and edge-based regions. Simulation results reveal that the proposed algorithm significantly lowers the blocking artifact, as judged by both objective and subjective measures.

Blocking effect is the major drawback in DCT-based (discrete cosine transformation) codecs at low bit-rates. In this paper, a post-processing filter is proposed in DCT frequency domain. The proposed algorithm uses a shift block within four adjacent DCT blocks to reduce computational complexity. By slightly modifying several DCT coefficients in the shift block, the artifacts that result from quantization and dequantization process are alleviated. The simulation results show that both visual perception and objective image quality are improved noticeably.

The blocking effect is the major drawback in discrete cosine transform (DCT)-based codecs at low bit rates. When a high compression ratio is required, boundaries between adjacent image blocks become visible. This kind of degradation probably will affect the judgment of an end user. In this work, a four-neighboring-block zero-masking technique is proposed in the DCT frequency domain. The proposed algorithm uses a shift block within four adjacent DCT blocks to reduce computational complexity. By slightly modifying several DCT coefficients in the shift block, the artifacts that result from quantization and dequantization processes are alleviated. The simulation results show that both visual perception and objective image quality are noticeably improved.