A variable rate adaptive transform coder for the digital storage of audio signals

A transform-coding algorithm, designed for the mass storage of variable-quality audio signals, is presented. The storage of both speech and music is considered. Automatic silence deletion and signal order, energy, and bandwidth estimation are employed to provide a continuously variable bit rate, adaptively matched to the characteristics of the input signal. Test results show that the algorithm offers storage savings of more than 75% over linear-PCM (pulse-code-modulation) coders, and more than 63% over equivalent quality log-PCM coders. Results also show improved performance over the CCITT standard wideband coder. The complexity of the algorithm is such that it can be implemented in real time on existing digital signal processors.<>