Block-based discrete cosine transform (BDCT) image coding techniques are widely used in image and video compression applications such as JPEG and MPEG. At a moderate bit rate, the BDCT is usually a quite satisfactory solution to most of practical coding applications. However, for high compression rates it produces noticeable blocking and ringing artifacts in the decompressed image. We propose a novel post-processing algorithm to remove the blocking and ringing effects at low bit rates. The main steps in this algorithm include block classification, boundary low-pass filtering and mid-point interpolation, edge detection and filtering, and DCT coefficient constraint. The improvement is demonstrated both subjectively and objectively.

The authors give exponential-type bounds on the probabilities of detection error under certain conditions. The bounds tend to zero rapidly as the sample size increases. These procedures are referred to as general information criterion (GIC) procedures since each is consistent and, under certain conditions, the rate of convergence of the estimate of the number of signals to the true value is rapid. The authors give bounds on the probability of wrong detection of the GIC procedure when the noise variance is unknown. Upper bounds on the probabilities of detection error are also obtained.>