Postprocessing to reduce blocking artifacts for low bit-rate video coding using chrominance information

We investigate a new postprocessing approach to reduce blocking artifacts in DCT-based video compression. Because blocking artifacts occur due to quantization of DCT coefficients, we effectively adjust the low-order DCT coefficients to remove discontinuities at block corners in smooth areas of the image. For blocking in detailed areas of the image, we camouflage black corners by adding a noisy dither to pixels around the block border. We demonstrate that chrominance variance can be used to efficiently identify blocks containing luminance detail. This postprocessing method is effective in reducing severe blocking effects that can occur at low bit rates. Examples from postprocessed H.261 video are given