[pulseaudio-discuss] question to recording with pa.

Lennart Poettering lennart at poettering.net
Sun Oct 25 17:11:25 PDT 2009

On Tue, 20.10.09 18:50, Alexey Fisher (bug-track at fisher-privat.net) wrote:

> Am Dienstag, den 20.10.2009, 17:15 +0100 schrieb Colin Guthrie:
> > 'Twas brillig, and Alexey Fisher at 20/10/09 16:02 did gyre and gimble:
> > > Thank you, the answer was clear. 
> > > Now i need to test what is cheaper: to reasample by pa or by aplication.
> > 
> > Please note that PA supports several different resamplers and the 
> > evaluation of "what is cheaper" could easily be invalidated by the user 
> > selecting a different resampler.
> > 
> > I'd advice you to generally let pulse worry about the resampling. Let 
> > the appropriate part of the stack deal with it in the way the user likes  :)
> > 
> > Col
> The question i made was a part of my investigation "what making my
> netbook on simple tasks so busy?" Currently ubuntu karmic use default
> "resample-method = speex-float-1" and it seems to be not optimal for me.
> More over, i use gnome-sound-recorder which is not really optimal too.
> For example: to record sound to speex, "audio/x-raw-float,rate=44100 ...
> speexenc" which make PA resampling stream. After i switched to
> "audio/x-raw-int" i reduced CPU usage to 5%. But i don't need
> "rate=44100" with speex i need "rate=16000", so we are back on resample.
> if i use "resample-method = ffmpeg" it seems to be better, but i don't
> wont to change anything in "/etc/pulse/*". So it will be probably better
> to use mplayer to record sound with internal resampler.

Not sure how the Atom actually handles FP, but usually embedded CPUs
tend to be shitty on FP, so I'd try to stay away from the float
resamplers for the Atom. Try speex-fixed-1 or so.

Verifying perfomance with "top" is not exactly the most scientific
way to do this... You might want to use oprofile or some other
profiler to get a better idea what exactly burns the CPU cycles and
where you need to optimize.


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

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