HAL timing issues
HAL timing issues
- Subject: HAL timing issues
- From: nick <email@hidden>
- Date: Tue, 5 Oct 2004 18:01:50 +0100
Hi
I'm writing a kernel mode CoreAudio driver for a USB device at the
moment, it's working well so far but I'm having fun (sic) trying to
figure out what's going on with the HAL during the first second or so
of audio (input) streaming.
What I'm seeing, from a little user-space test app, is that at first
the HAL seems to be getting audio pretty quick, only to then be
'throttled' before settling on a constant rate. At the moment this is
all pretty unscientific - i'm just seeing when my IOProc is being
called.
When I perform the same test with the Apple built-in audio device my
IOProc is called at constant intervals from the outset, and I don't see
this 'throttling' effect.
It's almost as if my device is running at a slower sample rate than HAL
expects... But this can't be the case - audio i record through it when
played back is at the correct pitch, for example.
Any ideas what the problem could be?
Thanks,
Nick
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