[FFmpeg-user] Noise in audio stream during quiet periods

[Julian Pilfold-Bagwell]

This is brilliant and possibly the fastest reply I've had on a mail list in
a very long time.

I'm back in work in the morning and will give it a go then and let you know
how I get on.

Thanks again for your time and help.

Julian

On Sun, 20 Feb 2022 at 11:59, Paul B Mahol <onemda at gmail.com> wrote:

> On Sun, Feb 20, 2022 at 12:33 PM Julian Pilfold-Bagwell <
> julian.pilfoldbagwell at gmail.com> wrote:
>
> > Thanks for getting back.  I was trying to insert a flag for noise
> reduction
> > into the command above but it always seemed to crash the moment I ran it.
> > Part of my question is what the correct format would be.
> >
>
> What flag? There is numerous examples on web how to use several audio
> ffmpeg filters.
>
> Like agate, afftdn, afwtdn, anlmdn, arnndn, anlms, anlmf.
>
> agate audio filter is recommended if you are extreme novice to ffmpeg.
>
> For example one possible invocation, of myriad possible combinations is:
>
> /usr/bin/ffmpeg -f alsa -i hw:0,0 -af agate=threshold=-40dB -acodec
> libmp3lame -ab 128k -ac 1 -content_type audio/mpeg -f mp3
> icecast://source:<password-removed>@172.20.0.75:8000/tannoy
>
> agate audio filter is there because it have very little latency and is very
> fast, but not much useful than just filtering out only when background
> noise is present and of certain signal to noise ratio.
>
> so threshold argument can be changed to actual dB of your background noise
> typically captured.
>
>
>
>
> >
> > On Sun, 20 Feb 2022 at 11:12, Paul B Mahol <onemda at gmail.com> wrote:
> >
> > > On Sun, Feb 20, 2022 at 12:03 PM Julian Pilfold-Bagwell <
> > > julian.pilfoldbagwell at gmail.com> wrote:
> > >
> > > >  Hi All,
> > > >
> > > >
> > > > I'm trying to set up a tannoy system in our building using FFMPEG and
> > > > Icecast.  The server that is streaming is being fed from the 0db
> > > recording
> > > > output from an analogue amplifier that is wired up to an existing
> 100v
> > > > system and at the receiving end are PCs with active speakers fitted.
> > > >
> > > > The problem that I have is that when there's no audio input to the
> > > tannoy,
> > > > there's a background noise that is intrusive enough to play out
> through
> > > the
> > > > speakers.  I've been trying to use the noise reduction features in
> > FFMPEG
> > > > to reduce the noise but haven't managed to get rid of it.  The
> command
> > > I'm
> > > > running to run the system is:
> > > >
> > >
> > > What noise reductions you tried?
> > >
> > >
> > > >
> > > > /usr/bin/ffmpeg -f alsa -i hw:0,0 -acodec libmp3lame -ab 128k -ac 1
> > > > -content_type audio/mpeg -f mp3 icecast://source:<password-removed>@
> > > > 172.20.0.75:8000/tannoy
> > > >
> > > >
> > > > Can anyone let me know if this is possible or if there's any way I
> > could
> > > > implement something akin to a radio squelch that would just mute the
> > > output
> > > > when the input signal drops below a certain level.
> > > >
> > > >
> > > > Thanks in advance,
> > > >
> > > >
> > > > Jools
> > > > _______________________________________________
> > > > ffmpeg-user mailing list
> > > > ffmpeg-user at ffmpeg.org
> > > > https://ffmpeg.org/mailman/listinfo/ffmpeg-user
> > > >
> > > > To unsubscribe, visit link above, or email
> > > > ffmpeg-user-request at ffmpeg.org with subject "unsubscribe".
> > > >
> > > _______________________________________________
> > > ffmpeg-user mailing list
> > > ffmpeg-user at ffmpeg.org
> > > https://ffmpeg.org/mailman/listinfo/ffmpeg-user
> > >
> > > To unsubscribe, visit link above, or email
> > > ffmpeg-user-request at ffmpeg.org with subject "unsubscribe".
> > >
> > _______________________________________________
> > ffmpeg-user mailing list
> > ffmpeg-user at ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-user
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-user-request at ffmpeg.org with subject "unsubscribe".
> >
> _______________________________________________
> ffmpeg-user mailing list
> ffmpeg-user at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-user
>
> To unsubscribe, visit link above, or email
> ffmpeg-user-request at ffmpeg.org with subject "unsubscribe".
>