Fighting Classic for CPU in audio callback
Fighting Classic for CPU in audio callback
- Subject: Fighting Classic for CPU in audio callback
- From: Brian Willoughby <email@hidden>
- Date: Mon, 19 May 2003 14:40:50 -0700
Hello all,
I have been working on a player for flac 1.1 files (Free Lossless Audio
Codec). It has been working flawlessly with the feeder thread using the time
constraint scheduling policy and double buffers of about 1 second each (less if
there are more than two channels). Typical Window Service activities, like
fidgety dragging of large windows or extreme magnification in the dock, have no
adverse effect on the playback.
I just discovered that Classic can cause audio stuttering when an application
running in Classic saves a file, even one that is only 8K. In this case, my
buffers may have been only 1/3 second because I was playing to a 6-channel
device - not sure if it was in 2-channel or 6-channel mode.
I have not set the priority or importance of the feeder thread. Is there a
minimum value I can use which will guarantee that my feeder thread will win any
battle with Classic? I know that it is best to stay below the CoreAudio
threads themselves, or else everything will stop working, but it be possible to
set my player between Classic and CoreAudio.
I noticed the problem running 10.2.6, but I would also like to know if Classic
has a higher or lower priority in 10.1.5 (and what that priority is).
Obviously, I can avoid Classic if there is no solution, but my hunch is that it
should not be too hard to beat Classic.
Brian Willoughby
Sound Consulting
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