(A) post filtering for reduction of blocking artifact and ringing noise in DCT-based image coding

Abstract

MPEG-4 and H.263++, which are under the standardization process, will include the post filtering. In this paper, a deblocking and deringing filtering method is presented, which enhances the subjective image quality by reducing the blocking effects and the ringing noise of the block-based image coding such as H.263+, H.263++ and MPEG-4. The proposed post filtering is applied to the reconstructed luminance and chrominance images of MPEG-4 VM 6 decoder so that the decompressed image of decoder can be enhanced in the visual sense. This method exploits one dimensional linear deblocking filter and one dimensional nonlinear signal adaptive filter which is based on the edge information. A one-dimensional deblocking filter is applied to the reconstructed luminance and chrominance images depending on the DCT coefficients position information. A one-dimensional ringing filter, which utilizes the horizontal and vertical edge information, is applied to the luminance image and chrominance images, after the deblocking operation, as well, where the filter coefficients are defined adaptively according to the binary edge information. The subjective image quality shows that the proposed post filtering reduces the blocking artifacts and the ringing noise when the images are highly compressed, and the computational complexity is approximately 1.6 times increased, where the peak signal to noise ratio (PSNR) is enhanced or sustained.