Frame-Adaptive Vector Quantization

Vector quantization (VQ) is a promising technique for low bit rate image compression. Recently image sequence compression algorithms based on VQ have been reported in the literature. Image sequences are highly nonstationary and generally exhibit variations from frame to frame and from scene to scene; hence using a fixed VQ codebook to encode the different frames/ sequences may not always guarantee a good coding performance. Several adaptive techniques which improve the coding performance have been reported in the literature. However, we note that most adaptive techniques result in further increases in computational complexity and/or the bit rate. In this paper, a new frame adaptive VQ technique for image sequence compression (FAVQ) is presented. This technique exploits the inter/ intraframe correlations and provides frame adaptability at a reduced complexity. A dynamic self organized codebook is used to track the local statistics from frame to frame. Computer simulations using standard CCITT sequences demonstrate the superior coding performance of FAVQ. In addition, FAVQ is a single pass technique which makes possible real time implementation.