Re: CPU Usage difference
Re: CPU Usage difference
- Subject: Re: CPU Usage difference
- From: Matthew Xavier Mora <email@hidden>
- Date: Mon, 09 Mar 2009 15:22:29 -0700
The problem is more likely the tool you are using to calculate CPU
usage. Under a light CPU load most of the time the CPU is either
throttled down or is turned off completely. Neither of these times are
subtracted by the tool which then reports inaccurate CPU usage. There
is more CPU load for speakers than line out because of speaker eq
processing but it the total CPU usage is very small and no where near
what is being reported. To correctly gauge the real CPU usage you have
to keep all the processors running full throttle, then you can use
existing CPU usage tools to see the true impact.
Matt
On Mar 6, 2009, at 4:43 PM, Alex ROUGE wrote:
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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