Discussion:
audio now all messed up after upgrading to 18.04
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Runner
2020-09-12 17:02:17 UTC
Permalink
Had been using external mics and such with 16.04. All controlled with
Pulseaudio. Lately, I'm noticing a LOT of distortion when trying to use
my external mic. Didn't have this before the upgrade. To describe the
sound, I would say it sounds like if you were to record audio at a very
low sampling rate, play it back, and hear the distortion. I tried
switching out mics and get the same distortion. No good for Zoom and
others if that is present. Pulseaudio seemed to upgrade to the current
version, 11.1. Perhaps I need to uninstall and reinstall a prior
version, but not sure how. Any thoughts would be welcome.
Dirk T. Verbeek
2020-09-13 09:08:26 UTC
Permalink
Had been using external mics and such with 16.04.  All controlled with
Pulseaudio.  Lately, I'm noticing a LOT of distortion when trying to use
my external mic.  Didn't have this before the upgrade.  To describe the
sound, I would say it sounds like if you were to record audio at a very
low sampling rate, play it back, and hear the distortion.  I tried
switching out mics and get the same distortion.  No good for Zoom and
others if that is present.  Pulseaudio seemed to upgrade to the current
version,  11.1.  Perhaps I need to uninstall and reinstall a prior
version, but not sure how.  Any thoughts would be welcome.
Have you tried adjusting the volume through pavucontrol?
Runner
2020-09-13 13:43:18 UTC
Permalink
Post by Dirk T. Verbeek
Had been using external mics and such with 16.04.  All controlled with
Pulseaudio.  Lately, I'm noticing a LOT of distortion when trying to
use my external mic.  Didn't have this before the upgrade.  To
describe the sound, I would say it sounds like if you were to record
audio at a very low sampling rate, play it back, and hear the
distortion.  I tried switching out mics and get the same distortion.
No good for Zoom and others if that is present.  Pulseaudio seemed to
upgrade to the current version,  11.1.  Perhaps I need to uninstall
and reinstall a prior version, but not sure how.  Any thoughts would
be welcome.
Have you tried adjusting the volume through pavucontrol?
Yes, I can adjust it there. I seem to have found a solution, or at
least a temporary one:

https://help.ubuntu.com/community/SoundTroubleshootingProcedure#Step_1

Particularly step 1B there where it says to reboot. Just killing
pulseaudio did not solve the distortion.

Of course, if I have to reboot each time to get rid of the distortion,
this is no good so still seeking a better solution.
Paul
2020-09-13 16:33:44 UTC
Permalink
Post by Runner
Post by Dirk T. Verbeek
Post by Runner
Had been using external mics and such with 16.04. All controlled
with Pulseaudio. Lately, I'm noticing a LOT of distortion when
trying to use my external mic. Didn't have this before the upgrade.
To describe the sound, I would say it sounds like if you were to
record audio at a very low sampling rate, play it back, and hear the
distortion. I tried switching out mics and get the same distortion.
No good for Zoom and others if that is present. Pulseaudio seemed to
upgrade to the current version, 11.1. Perhaps I need to uninstall
and reinstall a prior version, but not sure how. Any thoughts would
be welcome.
Have you tried adjusting the volume through pavucontrol?
Yes, I can adjust it there. I seem to have found a solution, or at
https://help.ubuntu.com/community/SoundTroubleshootingProcedure#Step_1
Particularly step 1B there where it says to reboot. Just killing
pulseaudio did not solve the distortion.
Of course, if I have to reboot each time to get rid of the distortion,
this is no good so still seeking a better solution.
You can use two computers, and have one send a sine wave to the other
for recording.

The purpose of sending known-patterns, is to better understand the
type of distortion. Whether it's clipping, echo or reverb and so on.

I find a common occurrence in modern times, is the notion of
"monitor mode" and "echo suppression". Monitor mode is where some
recording input is played through the speakers. In the case of
a microphone, this would result in a feedback loop and you'd get
a squeal. But the audio subsystem can also be using an echo
suppressor. And this can do things like "hollow out" the sound.
These processing steps also tend to make a mess of Zoom or
Skype or whatever.

Sine waves are good for checking signal quality. 440Hz would do.

Trapezoidal pulse signals, "drawn" in Audacity, can be used
to check for echo or reverb or "processing" type filters. The
idea is, you want to see if the distortion you hear is some
"effect" that should not be there.

A typical example is a sound driver, where the control panel
says "effects = None", and yet, by driving pulses through the
sound system, you can see this. A situation like this can
"muddy" classical music, but for rock doesn't seem so bad.

+----+ Called "concert hall" effect
| | +----+
----+ +----- ~~ ------+ +-------
Original Echo
0 msec 30msec

Now, I tried to set up a demo here with Audacity, and I'm
embarrassed to report, I "couldn't find the signal" :-/
No amount of Poettering with my setup could find the
signal so I could record it. Am I an idiot or what ?
There were only about a dozen things in the menu, and
none of them had a signal on it the audacity monitor could find.

if you can get the notion to work, it would be fine I guess...

Paul
Runner
2020-09-13 17:12:44 UTC
Permalink
Post by Paul
Post by Dirk T. Verbeek
Had been using external mics and such with 16.04.  All controlled
with Pulseaudio.  Lately, I'm noticing a LOT of distortion when
trying to use my external mic.  Didn't have this before the upgrade.
To describe the sound, I would say it sounds like if you were to
record audio at a very low sampling rate, play it back, and hear the
distortion.  I tried switching out mics and get the same distortion.
No good for Zoom and others if that is present.  Pulseaudio seemed
to upgrade to the current version,  11.1.  Perhaps I need to
uninstall and reinstall a prior version, but not sure how.  Any
thoughts would be welcome.
Have you tried adjusting the volume through pavucontrol?
Yes, I can adjust it there.  I seem to have found a solution, or at
https://help.ubuntu.com/community/SoundTroubleshootingProcedure#Step_1
Particularly step 1B there where it says to reboot.  Just killing
pulseaudio did not solve the distortion.
Of course, if I have to reboot each time to get rid of the distortion,
this is no good so still seeking a better solution.
You can use two computers, and have one send a sine wave to the other
for recording.
The purpose of sending known-patterns, is to better understand the
type of distortion. Whether it's clipping, echo or reverb and so on.
I find a common occurrence in modern times, is the notion of
"monitor mode" and "echo suppression". Monitor mode is where some
recording input is played through the speakers. In the case of
a microphone, this would result in a feedback loop and you'd get
a squeal. But the audio subsystem can also be using an echo
suppressor. And this can do things like "hollow out" the sound.
These processing steps also tend to make a mess of Zoom or
Skype or whatever.
Sine waves are good for checking signal quality. 440Hz would do.
Trapezoidal pulse signals, "drawn" in Audacity, can be used
to check for echo or reverb or "processing" type filters. The
idea is, you want to see if the distortion you hear is some
"effect" that should not be there.
A typical example is a sound driver, where the control panel
says "effects = None", and yet, by driving pulses through the
sound system, you can see this. A situation like this can
"muddy" classical music, but for rock doesn't seem so bad.
        +----+                               Called "concert hall" effect
        |    |               +----+
    ----+    +----- ~~ ------+    +-------
        Original             Echo
        0 msec               30msec
Now, I tried to set up a demo here with Audacity, and I'm
embarrassed to report, I "couldn't find the signal" :-/
No amount of Poettering with my setup could find the
signal so I could record it. Am I an idiot or what ?
There were only about a dozen things in the menu, and
none of them had a signal on it the audacity monitor could find.
if you can get the notion to work, it would be fine I guess...
   Paul
I know what happens to the audio when I hear it. I was initially using
Audacity to record the mic and then play back so I could hear what was
happening, then I found this command:

pactl load-module module-loopback

This will show up in the recording tab of pavucontrol. As I speak, I
can then hear myself and as long as the audio is low, I don't get
feedback.

It seems to be, judging from what I am hearing, that my audio is being
resampled somehow to a much lower rate. It would be like playing an
audio file originally recorded at at a native 44.1 Khz back at say 4
Khz. The amount of ringing and distortion would be terrible.

For now, I have reset the "avoid-resampling = false" in the daemon.conf
file to "true" so that hopefully nothing is automatically resampled for
now on. I understand that there was/is a bug that ignores the change,
however, so I'm just hoping that the bug has been fixed by now.

Another thing I found was highest sampling rate of my sound card did not
match the default sampling rate of PulseAudio. The sound card is 48000
Hz and PulseAudio was set to 44100 Hz. I have since changed the
daemon.conf "default-sample-rate" to 48000.

If I still find failure, will try additional steps. I had no such
issues before the upgrade from 16.04.
Runner
2020-09-13 20:11:31 UTC
Permalink
There's something else I've been trying, but having difficulty in one
respect. I want to be able to select my microphone and hear the output
on my speakers by making this selectable in Pulseaudio anytime I want to
hear myself. I referred to the instructions on this page:

https://wiki.archlinux.org/index.php/PulseAudio/Troubleshooting#Setting_the_sound_card's_sampling_rate_into_PulseAudio_configuration_(3/5)

If we scroll down the page to "Echo test", here is what it says:

"If you are unsure about your microphone setup, you can hear the input
from the microphone in real-time by enabling the loopback module (source):

$ pactl load-module module-loopback

The module will show up in the Recording tab of the pavucontrol program,
where the source and volume can be configured. While latency should be
low, it should be sufficient to get a feeling of the sound quality as
you will hear yourself speak in the microphone. To make the change
permanent, add the following pulseaudio configuration:

/etc/pulse/default.pa

load-module module-loopback

Watch out for feedback! Be ready to lower all volumes in case the
microphone picks up the output from the loudspeakers. Naturally, it is
better to run such a test with headphones."


The first part went ok and temporarily set up the selection in the
recording tab as indicated above. However, when I try and change the
config file to add the "load-module module-loopback" line, this seems to
break pulseaudio and it won't respond until the line is removed. Any
thoughts here would be welcome.
Paul
2020-09-13 23:23:24 UTC
Permalink
Post by Runner
There's something else I've been trying, but having difficulty in one
respect. I want to be able to select my microphone and hear the output
on my speakers by making this selectable in Pulseaudio anytime I want to
https://wiki.archlinux.org/index.php/PulseAudio/Troubleshooting#Setting_the_sound_card's_sampling_rate_into_PulseAudio_configuration_(3/5)
"If you are unsure about your microphone setup, you can hear the input
$ pactl load-module module-loopback
The module will show up in the Recording tab of the pavucontrol program,
where the source and volume can be configured. While latency should be
low, it should be sufficient to get a feeling of the sound quality as
you will hear yourself speak in the microphone. To make the change
/etc/pulse/default.pa
load-module module-loopback
Watch out for feedback! Be ready to lower all volumes in case the
microphone picks up the output from the loudspeakers. Naturally, it is
better to run such a test with headphones."
The first part went ok and temporarily set up the selection in the
recording tab as indicated above. However, when I try and change the
config file to add the "load-module module-loopback" line, this seems to
break pulseaudio and it won't respond until the line is removed. Any
thoughts here would be welcome.
https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/Modules/

"This allows one to route audio from a source directly back to a sink"

What could happen there, is maybe you break the connection of the
thing you wanted to hear in the first place.

*******

Whereas this one refers to using Stereo Mix in hardware. There is
a mux on the input ADC, which can select Mic or Line-In as a source,
but there is also a mux channel that connects to the Speakers, so you
can "listen" to your own speakers with the input ADC (and record what
is coming from the speakers). "Stereo Mix" or "What You Hear" (Nvidia name)
give a way to record Hollywood content.

https://wiki.debian.org/audio-loopback

At least with HDAudio and AC'97 sound, most all of those should have
Stereo Mix, although they're very coy about it and it's hard to find
documentation when you need it. Other sound types, such as PCI or
PCIe audio, anything is possible there, because the hardwares on those
boards, a few are "cobbled together" and may lack the level of
integration.

Paul

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