Comparative latency study of hardware and software pitch-trackers

In this empirical study, preliminary data show that current commercial hardware pitch-trackers are significantly faster than recently developed software pitch-trackers. Comparative analyses were made of the ZETA and the AXON interfaces, as well as the fiddle~ object (a real-time audio analysis tool) in the Opcode's MAX/MSP environment on a Power Macintosh 8500/120 (further studies are planned using a 400MHz machine).

A retropak-fitted ZETA violin was used to provide the audio input. The audio signal emitted by the ZETA pickup was sent independently to the ZETA VC-225 Violin MIDI Controller interface, the AXON AX-100 guitar interface, and the fiddle~ object, to be analyzed by their pitch-tracking algorithms. Both plucked and bowed (legato) articulations of the violin's open G and E strings were used as stimuli.

Once the pitch was analyzed, the interfaces and the fiddle~ object triggered a MIDI sound sample on a K2000R synthesizer. Both the acoustic audio signal and the output of the synthesizer were simultaneously recorded, then compared for latency times to see how fast the pitch-tracking algorithms were able to perform the pitch-to-MIDI conversion. The results show that the pitch-tracking of the AXON interface is faster than the ZETA interface and the fiddle~ object. For high-pitched sounds, on average, the AXON interface had latency times of 15-35ms. By comparison, the ZETA interface was slightly slower at 15-45ms, and the fiddle~ object's latency was 80-110ms. For low-pitched sounds, the latencies were 25-50ms for the AXON, 30-70ms for the ZETA, and 80-115ms for the fiddle~ object. In all cases, the pitches were correctly identified.