Re: kAudioUnitProperty_InPlaceProcessing
Re: kAudioUnitProperty_InPlaceProcessing
- Subject: Re: kAudioUnitProperty_InPlaceProcessing
- From: William Stewart <email@hidden>
- Date: Wed, 3 Feb 2010 18:59:00 -0800
An audio unit can process the samples provided in the input buffer
(from either a callback or a connection) and write the results of that
processing to that same input buffer (which will then get returned in
its result of AudioUnitRender)
You can imagine a chain of effects that all process in place. The top
of the chain gets an input from say a render callback. Then it
processes the audio in that buffer, returns that to its caller, etc,
on down the chain. So the bottom of the chain (which is the AU that
you called AudioUnitRender on) will get returned (if you called audio
unit render with mData ptrs in the ABL set to NULL) the original
buffer that was provided by the top's render callback.... make sense?
(If you look in the AUBase code, this is why in AUInputElement, you
call AudioUnitRender on a connected audio unit with the NULL ABL - it
can avoid a copy)
Bill
On Feb 1, 2010, at 7:41 AM, Paul Davis wrote:
i've read the docs, i've googled the web, and i'm still unclear on
what kAudioUnitProperty_InPlaceProcessing attempts to describe ...
with VST, the distinction between process() and processReplacing() was
fairly self-describing, but with the AU render model (host calls
plugin to render into specific ouput buffers -> plugin calls host's
render callback to get input buffers), i'm not so clear on what it
means to say that a plugin can or cannot do "InPlaceProcessing". any
chance of a clarification?
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