POST-PROCESSING TECHNIQUE FOR NOISE REDUCTION OF DCT-BASED COMPRESSED IMAGES

A new post-processing methodology reduces the unwanted noise artifacts present in the output images of DCT-based compressed signals. The method determines noise intensity in the region of each pixel of an image and filters each pixel corresponding to this noise intensity. This noise intensity includes ringing intensity and block noise intensity. Determining the noise intensity includes calculating a short range power spectrum and a long range power spectrum. A spectrum is identified as ringing if the short range power spectrum is negative and the long range long range power spectrum is positive. A spectrum is identified as block noise if the short range autocorrelation coefficient is positive and the long range autocorrelation coefficient is positive.