Multiframe blocking-artifact reduction for transform-coded video

A major drawback of block-based still-image or video-compression methods at low rates is the visible block boundaries that are also known as blocking artifacts. Several methods have been proposed in the literature to reduce these artifacts. Most are single image methods, which do not distinguish between video and still images. However, video has a temporal dimension that can lead to better reconstruction if utilized effectively. We show how to combine information from multiple frames to reduce blocking artifacts. We derive constraint sets using motion between neighboring frames and quantization information that is available in the video bit stream. These multiframe constraint sets can be used to reduce blocking artifacts in an alternating-projections scheme. They can also be included in existing set-theoretic algorithms to improve their performance by narrowing down the feasibility set. Experimental results show the effectiveness of using these multiframe constraint sets.