Variable Block Vector DPCM: Vector predictive coding of color images.

This memorandum describes Variable Block Vector DPCM that is a Vector DPCM method where the block size is changed depending upon the error of the prediction in each segment of the picture. This method initially assumes an 8 pixel x 8 pixel block size and then will reduce to four 4 pixel x 4 pixel blocks if excessive prediction errors result in detailed ares, and any of these 4x4 blocks can again be reduced to four 2x2 blocks for very detailed areas. The results of the variable block method demonstrates an approximately 40% improvement in bit rate as compared to conventional Vector DPCM. The bit rate for a color image ranges from approximately 1 bit/pixel for a excellent results to . 46 for good results. The variable block method also provides a more consistent image quality throughout all areas of the pictures processed.