Codebook adaptation algorithm for a scene adaptive video coder

Proposes a codebook adaptation algorithm for very low bit rate, real-time video coding. Although adaptive codebook design has been studied in the past, its implementation at very low coding rates suitable for the MPEG4 standard remains significantly challenging. The coder uses a standard motion compensated predictor with DCT quantization. It is unique in that it uses a hybrid scalar/vector quantizer to code predictor residuals. Bits are dynamically allocated to minimize distortion in the current frame, and scalar quantized blocks are used to adapt the VQ codebook. A codebook adaptation algorithm is described which uses an “equidistortion principle” and a competitive learning algorithm to continuously adapt the codewords. This training algorithm results in an increased use of the more efficient vector quantizer and improved video quality