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Handling interactions between channels in an AU
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Handling interactions between channels in an AU


  • Subject: Handling interactions between channels in an AU
  • From: Paul Cantrell <email@hidden>
  • Date: Thu, 24 Mar 2005 16:12:59 -0600

Please pardon my ignorance while I ask a very basic question about writing AUs.

I'm trying to write a very simple stereo imaging AU that deals with LR/MS processing, etc. As such, there are interactions between channels, and I need to deal with both input channels simultaneously in my processing method.

The sample code in SampleEffectUnit::SampleEffectKernel::Process seems to be saying very clearly that MyKernel::Process will receive interleaved samples:

while (nSampleFrames-- > 0) {
Float32 inputSample = *sourceP;
sourceP += inNumChannels; // advance to next frame (e.g. if stereo, we're advancing 2 samples);
// we're only processing one of an arbitrary number of interleaved channels
...etc...


However, reading the source for AUEffectBase and company, it really looks like it's instantiating one kernel per channel.

The documentation is -- with apologies to the AU team -- really piss poor. (I'm actually kind of surprised -- usually Apple puts out better stuff.) Parts of it seem to say that all AUs receive deinterleaved samples; other parts seem to say that they should support interleaved or deinterleaved. There is no real explanation of implementing MyKernel::Process to speak of, other than the sample code I pasted above.

Looking around the code and the web, it looks like I need to override AUEffectBase::Render or AUEffectBase::ProcessBufferLists or ... something.

Can anybody point me in the right direction?

Cheers,

Paul


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"Prediction is hard, especially of the future."  -- Niels Bohr

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