Le 08/11/2017 à 12:43, Tanu Kaskinen a écrit :
On Tue, 2017-11-07 at 15:29 +0100, [email protected] 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?)
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