[arm-allstar] Distorted audio (sampling?)

Sun Sep 15 18:00:15 EDT 2019

This is very strange behavior. When the audio issues are occurring, do you 
see any kernel error messages?  From a bash command prompt, use the 
"dmesg" command to see the kernel/console messages.

A marginal or faulty 5V power supply would be my #1 suspect. A reboot
radically changes the power supply load, which might temporarily snap it
back to proper operation (I have experienced this with a wall wart
supply)...OR, perhaps some type of ground loop or RF/noise getting into
the low-level analog audio.....I have experienced ground loop noise that
comes and goes.

73, David KB4FXC

On Sun, 15 Sep 2019, Alessio Sacchi wrote:

> Thanks David. Got some samples converted.
> 
> Restarting asterisk did not solve the proble. Rebooting the PI fixed it
> twice - after the first reboot I described above, it started degrading
> again and I had to restart the RPi again after about 24 hrs. We are now
> running since 3 days from that restart and audio is still good. But most
> importantly no - stopping and starting asterisk was not helping at all.
> 
> Alessio
> 
> On Sat, Sep 14, 2019 at 2:05 AM David McGough <kb4fxc at inttek.net> wrote:
> 
> >
> > Alessio,
> >
> > Interesting that rebooting the RPi3B fixes the issue. Does stopping and
> > starting Asterisk also fix the issue?
> >
> > To convert uLAW (pcm) files to wav files, one way is with the sox
> > software, like:
> >
> > sox -t ul -c 1 -r 8000 allstar_audio_file.pcm  output_file.wav
> >
> >
> > 73, David KB4FXC
> >
> >
> > On Fri, 13 Sep 2019, "Alessio Sacchi via ARM-allstar" wrote:
> >
> > > Danny, David
> > >
> > > I could certainly take a generator up to the site on my next trip.
> > Speaking
> > > of adding a tone, I remember I used a "generate continuous tone" in ASL
> > > usb-tune tool. That helped me at quantifying the distortion back in my
> > ASL
> > > testing days.YOu kept it running for seconds and the tone broke up
> > > intermittently eventually.
> > >
> > > There's a quite important update on the degraded audio issue. I continued
> > > my controlled manner testing by disabling things one by one.
> > Specifically I
> > > had a script checking gpio to sense loss of mains power - killing it
> > > doesn't change anything. I eventually tried a reboot which fixed the
> > > problem immediately. But the issue come back in the same form less than
> > 24
> > > hours later. Users reported this thing gets worse over time. Another
> > reboot
> > > fixed it again. I am back doubtful of my power supply, unless you have
> > > other ideas. Am I wrong thinking 3 ports could be too many for a single
> > PI
> > > 3B?
> > >
> > > I'll procure some uLAW recordings as soon as I can listen to them. What
> > do
> > > you reckon to play the uLAW files with? I tried  importing them as raw
> > > files with audacity with no luck.Maybe I am configuring it wrongly during
> > > the import.
> > >
> > > Thanks,
> > > Alessio
> > >
> > > On Thu, Sep 12, 2019 at 5:46 PM "Danny K5CG via ARM-allstar" <
> > > arm-allstar at hamvoip.org> wrote:
> > >
> > > > Alessio,
> > > >
> > > > It sounds like you need to do some testing in a controlled manner to
> > > > eliminate as many unknowns as possible.
> > > >
> > > > Do you have a service monitor? Generate input RF, add a tone, record
> > it.
> > > > Is the distortion still there?
> > > >
> > > > Danny
> > > > K5CG
> > > >
> > > > ----- Original Message -----
> > > > From: "ARM Allstar" <arm-allstar at hamvoip.org>
> > > > To: "ARM Allstar" <arm-allstar at hamvoip.org>
> > > > Cc: "Alessio Sacchi" <iz4efn at gmail.com>
> > > > Sent: Thursday, September 12, 2019 9:55:51 AM
> > > > Subject: Re: [arm-allstar] Distorted audio (sampling?)
> > > >
> > > > Hi David, thanks. I will immediately begin recording with uLAW and
> > find a
> > > > few samples to share.
> > > >
> > > > >>is the same noise heard on all your AllStar connected receivers or
> > just
> > > > one?
> > > > All connected receivers. To clarify:
> > > > - A distorsion over a signal coming from the 50MHz port is heard on
> > > > echolink, on 70cm and on 23cm
> > > > - Distorsion can happen regardless of the input ports - except for
> > audio
> > > > coming from echolink. Meaning that signals coming from each of the
> > radio
> > > > ports can be affected by distorsion. Audio from echolink seems to be
> > pushed
> > > > out clean at all times.
> > > >
> > > > Alessio
> > > >
> > > > On Thu, Sep 12, 2019 at 4:01 PM "David McGough via ARM-allstar" <
> > > > arm-allstar at hamvoip.org> wrote:
> > > >
> > > > >
> > > > > BTW, I noticed that the dropbox .wav files are in the GSM CODEC
> > format.
> > > > > For diagnosing audio issues, I recommed saving the files using the
> > much
> > > > > higher audio quality uLAW CODEC, rather than GSM. The negative
> > drawback
> > > > is
> > > > > that the files will be bigger, of course.
> > > > >
> > > > > To enable saving uLAW formatted files, in your /etc/asterisk/rpt.conf
> > > > file
> > > > > node stanzas, add:
> > > > >
> > > > > archivetype=pcm
> > > > >
> > > > >
> > > > > 73, David KB4FXC
> > > > >
> > > > >
> > > > > On Thu, 12 Sep 2019, "David McGough via ARM-allstar" wrote:
> > > > >
> > > > > >
> > > > > > Hi Alessio,
> > > > > >
> > > > > > To me, the distortion heard in your recordings doesn't sound it's
> > > > coming
> > > > > > from the HamVoIP/AllStar software. My first suspicion is noise on
> > the
> > > > > > receiver audio, which leads me to a question: is the same noise
> > heard
> > > > > > on all your AllStar connected receivers or just one?
> > > > > >
> > > > > >
> > > > > > 73, David KB4FXC
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > > _______________________________________________
> > > > >
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> > > > >
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> > > > >
> > > > _______________________________________________
> > > >
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> > > > ARM-allstar at hamvoip.org
> > > > http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar
> > > >
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> > > > _______________________________________________
> > > >
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> > > > ARM-allstar at hamvoip.org
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> > > >
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> > > >
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> > >
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> > >
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> > >
> >
> >
> 