Enable matrix mixer inputs without ramping
Enable matrix mixer inputs without ramping
- Subject: Enable matrix mixer inputs without ramping
- From: Sean Dougall <email@hidden>
- Date: Mon, 14 Dec 2009 13:08:33 -0800
Hi list,
Here's the simplified scenario: Our app routes playback of audio files
through matrix mixers, so that we can play back a number of audio
files, each channel of audio getting its own input bus on the matrix
mixer that feeds the output device.
Problem is, the app doesn't always have a lot of lead time (if any)
before an audio file starts playing, because it doesn't have a strict
DAW-style timeline. So it needs to be able to enable the input bus
immediately. What we're doing is:
err = AudioUnitSetParameter( _mixerUnit,
kMatrixMixerParam_Enable,
kAudioUnitScope_Input,
bus, // bus number getting passed in
flag, // YES when audio starts playing, NO when it stops
0 );
This is resulting in a quick but decidedly non-zero ramp time (on the
order of 10 ms), which causes playback artifacts in some cases. But we
can't just leave all the inputs enabled, because we can't predict
ahead of time how many inputs it'll need at any given time (and CPU
usage gets really hairy if we leave a generous enough number of inputs
open).
I've tried using AudioUnitScheduleParameters() instead, but no love.
Is there a sensible way to immediately enable a mixer input?
Thanks!
Sean Dougall
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