SR conversion and AUHAL
SR conversion and AUHAL
- Subject: SR conversion and AUHAL
- From: Bjorn Roche <email@hidden>
- Date: Thu, 8 Dec 2005 10:54:44 -0500 (EST)
Hey CoreAudio folks,
I've been squinting at code and docs for a long time here, so
sorry if I am missing something obvious. Anyway, I understand from here:
http://developer.apple.com/technotes/tn2002/tn2091.html#FORMATS
that AUHAL does NOT provide sample rate conversion when doing input. I
think I saw a mailing list posting to that effect as well.
However, the PDFs on CoreAudio state:
An application can use an AudioOutputUnit to interface to a device. The
DefaultOutputAudioUnit tracks the selection of a device by the user as the
default output for audio, and provides additional services such as sample
rate conversion, to provide a simpler means of interfacing to an output
device.
So my conclusion was: "AudioOutputUnit does SR conversion for output, but
not input, so I will need to take care of input SR conversion myself using
an AudioConverter"
All well and good, but when I tried, I noticed I always had buffer
under/over-runs, so I skipped the conversion and everything seems to work
fine, and I get the same number of frames in and out over the long run.
It's entirely possible that I am not setting the sample rates correctly,
or something else dumb, but I'd like to clarify:
When, if ever, do I need to do SR conversion when using AUHAL?
TIA,
bjorn
-------------
Bjorn Roche
Check out my CD Mastering Software
for Mac OS X : http://www.xowave.com
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