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

21naown at gmail.com 21naown at gmail.com
Wed Nov 8 14:31:27 UTC 2017

Le 08/11/2017 à 12:43, Tanu Kaskinen a écrit :
> On Tue, 2017-11-07 at 15:29 +0100, 21naown at gmail.com wrote:
>> If you cannot be 100% sure, is any problem replaced by a 0dB sound? If
>> so, then I can check for a possible problem with Audacity and
>> Sample Data Export. For example, if an underrun or a rewind occurs, is
>> it replaced by 0dB by PulseAudio? Or it is a random value?
> If an underrun happens inside PulseAudio (i.e. an application doesn't
> provide data fast enough), the missing audio is replaced with silence.

Very good news!

> 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”?).

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?)

More information about the pulseaudio-discuss mailing list