Re: CPU Usage difference
Re: CPU Usage difference
- Subject: Re: CPU Usage difference
- From: Alex ROUGE <email@hidden>
- Date: Sat, 7 Mar 2009 01:43:44 +0100
So,
I set all devices, internal speaker and lineout / headphone to be
44100hz
The mp3 file is 44100hz
The same phenomena occured.
If you want me to perform other test I'd be pleased to do so.
I already did a few of them and the result is always the same. With
internal speaker it's 3 to 4 times more cpu consuming.
I also ask friend who had the same issue with Macbook (not sure how it
works with Macbook Pro but friend told me they didn't had this
behavior).
Regards
Alex
On 7 mars 09, at 01:30, William Stewart wrote:
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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