Re: CPU Usage difference
Re: CPU Usage difference
- Subject: Re: CPU Usage difference
- From: William Stewart <email@hidden>
- Date: Fri, 6 Mar 2009 16:30:28 -0800
Could you tell me:
What is the sample rate of the file
What is the sample rate of the device - have a look at this in Audio
MIDI Setup
Thanks Alex
Bill
On Mar 6, 2009, at 3:24 PM, Jens Alfke wrote:
What I found is that, all application who requiere audio output
doesn't have the same CPU usage depending if the audio output is
internal speaker or headphone/line out.
The difference is impressive.
For instance, if we use the Finder to play an audio file :
Line out : CPU charge = 3.5%
Internal speaker : CPU charge = 10.9%
I think Apple ® is doing a software filtering to compensate very
small sized speaker but this difference is really huge.
The speaker and line-out interfaces may be running at different
sample rates. (I've seen this myself; I had a bizarre bug that was
triggered by plugging in headphones. Turned out this reset the HAL
to change between 44k and 48k.) That would mean that sample-rate
conversion is involved in playback over one or the other interface.
If you're curious you could always run 'sample' or Xray on the app
while it's playing, and see where the time goes.
—Jens
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