[pulseaudio-discuss] CPU usage of pulse audio-0.9.5-r4 is at 25-30%

Lennart Poettering lennart at poettering.net
Tue Jul 24 17:32:09 PDT 2007

On Fri, 13.07.07 23:54, Rémi Cardona (remi at gentoo.org) wrote:

> Lennart Poettering a écrit :
> > This is probably related to the fragment settings that have been
> > chosen by PA. The smaller the sound card fragment sizes are the higher
> > will be your CPU load. Its a tradeoff between latency and CPU
> > load. You can pass different fragment settings to the ALSA or OSS
> > modules of pa and thus influence the CPU load.
> I did some very basic profiling on one of my slower boxes and PA is 
> spending a lot of time in one of libsamplerate's functions.
> It looked to me as though PA was doing resampling/conversions when both 
> the card and stream are standard 44.1k 16bit samples (from mp3s and
> CD).

Are you sure that the full sample types match entirely? channels?
rate? endianess? sample type? if so, than pa shouldn't do any
resampling, unless the stream has been marked as "dynamic sample rate"
stream, which is used for modules like module-combine where the sample
rate constantly changes, although initially input and output formats
might match 100%.

> Lennart, I'll be going to Guadec on Sunday, I'd like to show this to you 
> if you're interested.

Hmm, unfortunately we didn't discuss this issue back at GUADEC...


Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net         ICQ# 11060553
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

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