Our application is pulseaudio only. So in this case I suppose that Jack must be interconnected with pulseaudio. Do you think that even interconnected, I wouldn't have cpu usage problems ? Concerning the remap module, without remap the virtual device is not visible by our application... Thanks a lot for your time.
Renaud Le ven. 5 févr. 2021 à 02:15, Sean Greenslade <s...@seangreenslade.com> a écrit : > On Thu, Feb 04, 2021 at 06:29:47PM +0100, Renaud GHIA wrote: > > >> Thank you for the tip. > > >> Now I am sure that resampling does not apply (see below). > > >> But unfortunately pulseaudio always consumes 30% of one CPU core! > > >> > > > > > > The reason is that you are using module-loopback. Due to a potential > > > difference between the clocks on the null sink and on the real sound > card > > > (even though both report 44100 Hz), it always has to resample in order > to > > > correct for the clock skew. If you don't understand, here is an > analogy: > > > you have two mechanical watches. Even though both claim that their hour > > > hand makes one full circle every 12 hours, in fact, if left unattended, > > > they will diverge over time. There is no way to avoid that, except by > > > moving to Jack or PipeWire which simply don't introduce a null sink > with an > > > independent clock. > > > > > > If you decide to stay on PulseAudio, you can tweak the resampling > method. > > > The default, speex-float-1, is light on the CPU resources and should > > > produce no distortions detectable by human ear on typical speech and > music. > > > It does produce easily detectable distortions on specifically crafted > > > signals. If you want to make sure that the resampler is transparent no > > > matter what is thrown at it, use speex-float-5. There is no point in > going > > > higher than that. > > > > Thanks for your response. > > I understand the problem of clock drift when we have several audio > hardware > > devices (with different qwartz). > > But here, it's a pity that the null video driver has an independent > clock... > > Concerning pipewire, for now it doesn't work with our particular > > application (no sound), but it seems to evolve quickly. > > I haven't tried jack for now, but if it depends on pulseaudio, won't I > have > > the same problem? > > Jack doesn't depend on pulseaudio, it's an independent sound server. > Though there are ways to make the two interconnect. > > As far as I know, jack solves this problem by only allowing one hardware > sound device and locking all clocks to that. See: > > https://jackaudio.org/faq/multiple_devices.html > > One thing that just occured to me was to ask whether you acutally need > to use the remap module at all. I just did a quick test on a very weak > machine of mine: a null sink, a music player outputting to that sink, > and ffmpeg recording the null sink's monitor-source, all with matching > 44.1 kHz sample rates. This resulted in no resamplers in the chain, and > only 9% CPU usage on a 2010 Atom CPU. > > --Sean > > _______________________________________________ > pulseaudio-discuss mailing list > pulseaudio-discuss@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss >
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