Currently, the demands of video communication on low bit-rate channels (10kb/s~60kb/s), such as wireless channel and telephone network, are becoming more and more comprehensive. Although some existed international video coding standards, such as H.261, H.263, MPEG-1 and MPEG-2, has wined great success in all kinds of commercial applications. But for all these standards, the phenomena of sensible blocking artifacts or image dithering will emerge under narrow bands, which impair the visual quality ...