A 2-channel, 16-bit digital sampling frequency converter for professional digital audio

A digital sampling frequency converter for arbitrary ratios of sampling frequencies is presented. It is based on a multistage interpolating filter, and on a novel time-domain control of the filter stages by signals derived from the sampling frequency clocks. Time-domain resolution of ±300 picoseconds is obtained, compatible with digital audio of 16-bit resolution. In addition to the filter design and implementation, measurement results are presented. They indicate that 16-bit accuracy is indeed achieved, even with asynchronous, drifting and time-varying sampling frequencies. A number of applications (digital mastering, program transfer between conflicting digital audio formats, pitch control with constant sampling frequency in digital recorders, error concealment, interfaces in digital transmission) are presented.