Re: Glitches when using "Sound Manager" APIs under Mac OS X
Re: Glitches when using "Sound Manager" APIs under Mac OS X
- Subject: Re: Glitches when using "Sound Manager" APIs under Mac OS X
- From: Jeff Moore <email@hidden>
- Date: Thu, 11 Dec 2003 12:30:52 -0800
The Sound Manager doesn't have any feeder threads of it's own. Rather,
it does all it's work, including calling your SndChannel callback, from
the HAL's IO thread. So there are lots of ways to introduce glitching
depending on how you are using the API. Could you provide a bit more
detail about what you are doing, especially about what APIs you are
calling from which threads and the sizes and formats of your
bufferCmd's?
Thanks!
On Dec 11, 2003, at 8:49 AM, Sylvain Demongeot wrote:
Hello.
My app uses the "Sound Manager" APIs (SndDoCommand) to output sounds
under
Mac OS X.
I get glitches under Panther when the CPU is very active (eg when
minimizing).
This is not a problem with the feeder thread's priority (the buffers
are
large enough so the feeder thread is never too late).
Rather, I would say the priority of the Sound Manager (or QuickTime if
you
prefer) itself is too low to get the "bufferCmd" job done in time.
This is very weird -- it used to work quite well.
Apple's own sample code, "SoundPlayer", suffers from glitches (even
when
buffers are set large enough for cycles of more than 1 second).
On the other hand, the "Million Monkeys" Core Audio sample works
perfectly
in the same situations (the feeder thread must have at least a fixed
priority).
Does this mean QuickTime feeds Core Audio with a thread with low
priority?
Are the Sound Manager APIs useless under Panther? Is Core Audio
required for
glitch-free sound output?
Thanks for your thoughts,
Sylvain
--
Sylvain Demongeot - The Wild Bits
http://www.wildbits.com/
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--
Jeff Moore
Core Audio
Apple
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