[pulseaudio-discuss] How to check visually for XRUNs/drop-out/interruptions and similar in PulseAudio?

Tanu Kaskinen tanuk at iki.fi
Thu Nov 9 11:41:50 UTC 2017

On Wed, 2017-11-08 at 15:31 +0100, 21naown at gmail.com wrote:
> Le 08/11/2017 à 12:43, Tanu Kaskinen a écrit :
> > The issues with rewinds were about monitor sources and resampling. If I
> > understood correctly, your source material is in 48000 Hz and Jack is
> > configured with that rate too, so there's no need for resampling, and
> > you haven't mentioned recording from a monitor source either, so there
> > should be no reason to be concerned about rewinds. If rewinds happen,
> > they shouldn't cause any glitches.
> > 
> > But if you're curious, the monitor source bug causes short chunks of
> > audio to be duplicated in the recording stream. I haven't seen concrete
> > examples of what kind of glitches resamplers can have, but my intuition
> > is that one sample in the audio stream might have a significant
> > adjustment towards zero, and a few samples after that might have
> > slightly wrong values.
> > 
> I give you my audio chain more precisely:
> Playing = Audio file (to simplify) → PulseAudio (→ 
> pulseaudio-module-jack) → Jack → Audacity = Recording
> “Audio file” means the audio source is in the computer, it is not taken 
> by a microphone for example (is this is what you said by “monitor 
> source”? Or you talk about the tab in pavucontrol “Recording → Audacity 
> → Monitor of SOMETHING”?).

I'm talking about that "Monitor of SOMETHING". Audio devices in
pulseaudio are represented by sinks (playback devices) and sources
(capture devices). Each sink has a monitor source associated with it,
and the monitor source can be used to record what is being played to
the sink.

Since you're recording from jack and not from pulseaudio, you're
definitely not using any monitor sources.

> Settings like the sample rate/number of channels/… are set to be the 
> same for my entire audio chain, to avoid possible sound modifications 
> like resampling. Yes I think it will not be more than 48000 Hz / 2 channels.
> As you said, duplicated values (plus you said it is a bug) are related 
> to rewinds. So no rewinds in the log = no possible duplicated values.
> If I understood, in my case, you cannot confirm 0 dB is the only result 
> I could have in case of problems? (because you think I can have other 
> problems than underruns?)

Underruns are the only problem that you can have, unless there's
something that I haven't thought of.



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