Dana Massie - Sample rate conversion with MaxSRC
A digital method for sample rate conversion using recursive IIR “phasor” filters, denoted MaxSRC, named in honor of Max Mathews whose work popularized the term “phasor filter". High quality sample rate conversion is useful for many applications in computer audio and music, including sound synthesis and sampled waveform playback. The most common methods used historically for sample rate conversion use FIR filters. MaxSRC uses time-varying IIR filters.
The methods and corresponding systems provide asynchronous conversion of sampling rate frequencies and utilize phasor filters for converting an input signal having a first sampling rate into an output signal sampled in an arbitrary sequence of sampling times. The conversion process provides a sequence of sets of complex numbers representing a filtered version of the input signal. More specifically, the conversion process includes the calculation of values of the output signal by multiplying (e.g., scaling) the sets of complex numbers by a corresponding set of complex phasors, the complex phasors corresponding to the timing of the arbitrary time sequence to obtain a corresponding set of real results with the value of the output signal being a weighted sum of the real results. The filtering can be viewed as a projection of the input signal onto a set of basis functions, represented as first-order complex recursive filters.
Dana Massie is the director of DSP architecture at Audience, Inc., a company developing chips for audio enhancement on mobile phones based on models of the human auditory pathway. His professional interests include DSP algorithm development & implementation including VLSI architectures for DSP.
Dana worked as manager of audio hardware at Apple Computer, DSP algorithm developer at Waves, Inc., DSP algorithm developer at NeXT Computer, working for Julius O. Smith.
Massie was Director of Creative Technology Advanced Technology Center, where he led the development of the EMU10K1, a multi-media coprocessor for PCs that accelerated Environmental Audio Extensions, the 3D audio API that Massie evangelized at Creative. Before that, Massie was at E-mu Systems, a computer music instrument company that pioneered the dedicated sampler as a musical instrument.