APTX White Paper Sample

This paper discusses some of the research undertaken in developing a high quality audio codec for wireless audio streaming applications. The selection of a sub-banding filter and its impact on the computational requirements of the codec are discussed, with the selection of a CDF 9/7 based wavelet packet decomposition filter as the optimal choice in terms of quality and complexity. We also describe the use of conditional coefficcient update techniques to reduce the average computational requirements of an LMS prediction algorithm as used in an ADPCM codec. We demonstrate how this adaptive prediction technique can be used to reduce complexity without adversely affecting quality.