A rapidly adaptive lossless compression algorithm for high fidelity audio coding

A new adaptive algorithm for lossless compression of digital audio is presented. The algorithm is derived from ideas from both dictionary coding and source-modeling. An adaptive Lempel-Ziv (1977) style fixed dictionary coder is used to build a source model that fuels an arithmetic coder. As a result, variable length strings drawn from the source alphabet are mapped onto variable length strings that are on average shorter. The authors show that this algorithm outperforms arithmetic coding or Lempel-Ziv coding working alone on the same source (in their experiments the source is an ADPCM quantizer). Adaptation heuristics for the Lempel-Ziv coder, relevant data structures, and a discussion of audio source modeling (entropy estimation) experiments are described. While the algorithm presented herein is designed to be used as a post-compressor in a lossy audio transform coding system, it is well suited for any instance where non-stationary source outputs must be compressed