Re: AUMixer sub-buffer delay?
Re: AUMixer sub-buffer delay?
- Subject: Re: AUMixer sub-buffer delay?
- From: Chris Rogers <email@hidden>
- Date: Tue, 2 Aug 2005 11:56:24 -0700
Evan,
There isn't any latency in the mixer. I'm not sure what's going on
here, but you may want to call AudioUnitReset() on the mixer before
you start your fade. This deactivates the smoothing de-zippering the
first time you make a call to AudioUnitSetParameter()
so it will snap to the exact param value.
Chris Rogers
Core Audio
Apple Computer
On Aug 2, 2005, at 6:46 AM, Evan Olcott wrote:
Hey folks!
Working on cleaning up Wave Editor, and came across an interesting
issue with the AUMixer.
Fade objects are actually AUMixers that I automate. On a pre-
render, I find the value of the volume at the given point in time,
then I call AudioUnitSetParameter() on the AUMixer's volume. It
then continues on with the render, and all is good.
My problem is that the AUMixer doesn't seem to be setting the
parameter for the first *half-buffer*... My running buffer size
seems to be 512, and the first 256 samples are untouched. (!!?!)
Most apparent example: I have a fade-*in* from the beginning of a
file, the pre-render is called, the AUMixer volume parameter is set
to 0. Then the render takes place. If I look (& listen) closely,
the first 256 samples are as they were, but 257-511 are zero'd out
(or at least lowered WAAY down) as they should be. The rest of the
fade continues and sounds as it should.
AUMixer doesn't register any latency - why would the first *half-
buffer* of audio pass through untouched, after I've already told
the AUMixer what it's new parameter is?
Ev
Technical Knowledge Officer
Head Programmer/Designer
Audiofile Engineering
http://www.audiofile-engineering.com/
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