关键词: 块效应, 块离散余弦变换, 凸集投影, 量化约束集

Abstract: At low bit rates，the Block Discrete Cosine Transform（BDCT） compression methods often give rise to blocking artifacts.In various approaches to the problem，Quantization Constraint Set（QCS） is widely used as a priori information about the coding process.In this paper，we propose a modified constraint set based on the statistical property of quantization errors.The experimental results show that while combined with typical POCS-based algorithms，the proposed QCS outperforms traditional QCS and produces results comparable with those achieved by narrow quantization constraint set（NQCS）.

Key words: blocking artifacts, Block Discrete Cosine Transform（BDCT）, Projection Onto Convex Sets（POCS）, Quantization Constraint Set（GCS）