Pitch shifting
Pitch shifting
- Subject: Pitch shifting
- From: Martin Hairer via Coreaudio-api <email@hidden>
- Date: Thu, 19 Mar 2020 12:17:28 +0000
Dear all,
When trying to apply a pitch shifting effect on a pure sine wave using
kAudioUnitSubType_NewTimePitch I always end up with a discontinuity at around
15870 samples (360ms @ 44.1kHz). This appears independent of the amount of
pitch shifting and of the sampling frequency. It even happens if I start off
with 100ms of silence and then 30ms of ramping up the sine wave from 0 to 50%.
When using kAudioUnitSubType_TimePitch instead the situation is worse: I get a
whole bunch of localised artefacts at various (not periodic) locations up until
about 2-3 seconds in.
Does anyone have an idea of what might be going wrong? Note that if I keep the
exact same code and just replace kAudioUnitSubType_NewTimePitch by
kAudioUnitSubType_Varispeed then I don't get any artefacts which seems to rule
out a problem with any buffering on my end. Also, the discontinuity is quite
sharp, but goes over more than one single sample as would be the case if it's a
buffering problem. The artefacts created by kAudioUnitSubType_TimePitch are a
mixture of sharp (10-15 samples) discontinuities and amplitude fluctuations.
Thanks a lot in advance!
Martin
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