The visual quality of compressed images and video is Low bit rate image/video coding is essential for many visual generally affected by three factors: data source, coding bit communication applications. When bit rates become low, most rates, and compression algorithms. For a given comprescompression algorithms yield visually annoying artifacts that sion method, more information (motion or spatial details) highly degrade the perceptual quality of image and video data. contained in the source signal requires more bits for repre-To achieve high bit rate reduction while maintaining the best sentation. When compressed at the same bit rate, images possible perceptual quality, postprocessing techniques provide with more details usually degrade more than those with one attractive solution. In this paper, we provide a review and fewer details. The coding bit rate is another important analysis of recent developments in postprocessing techniques.
factor that determines quality. In lossy compression, there
Various types of compression artifacts are discussed first. Then, is a trade-off between the bit rate and the resulting distortwo types of postprocessing algorithms based on image enhancement and restoration principles are reviewed. Finally, tion. The lower the bit rate, the more severe the coding current bottlenecks and future research directions in this field artifacts due to loss of information. Furthermore, the type are addressed.