Enhancement of coded video sequences via an adaptive nonlinear post-processing

摘要

Most video data compression standards use block-based motion estimation and the discrete cosine transform. This scheme takes advantage of the local spatial correlation property of images. However, it induces the well-known blocking artifacts, corner outliers, and ringing noise when the image is highly compressed. Conventional 2-D techniques for contrast sharpening cannot be applied to the enhancement of block-coded image sequences, because they emphasize such artifacts that become very visible and annoying in an image sequence. The local spectra and bandwidth of both the noise and the signal vary spatially, and the characteristics of the filters need to be locally adapted.For this purpose, in this paper we present a computationally simple post-filtering method that enhances the true details, limits the overshoot near sharp edges and attenuates the coding artifacts. Moreover, a mechanism is proposed that allows the behaviour of the filter to change according to the presence and the intensity of the coding artifacts. To this purpose, we also introduce a new distortion measure for blocking and ringing artifacts.