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

[Paul B Mahol]

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
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