A Low Bit-Rate Image Sequence Coder Combining a Progressive DPCM on Interleaved Rasters with a Hybrid DCT Technique

An image sequence coding scheme for transmission at 384 kbits/s and 64 kbits/s is presented. In comparison to known schemes, picture quality in still picture areas is improved without impairing the rendition of temporally changed areas. Bit-rate reduction is obtained by a conventional hybrid DCT coding technique in changed areas, and a predictive coding technique using a raster interleaving approach to update still picture areas. Preferentially treating the image signal in still areas with a not-block-oriented coder yields in these regions a reconstruction with full spatial resolution and free of any block effects. Experimental results are presented confirming that the quality in still picture areas is improved compared to that of known low bit-rate image sequence coding schemes, while the quality in changed areas is maintained.