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

[Paul B Mahol]

On Mon, Feb 21, 2022 at 12:34 PM Julian Pilfold-Bagwell <
julian.pilfoldbagwell at gmail.com> wrote:

> Hi Paul,
>
>
> Well, that certainly did the job with the only mod being the db level
> going to -20.
>

That is too low quality or perhaps if you do not use RMS detector but peak
one than threshold could get lower...


>
> Thanks again for your help, really appreciate it.
>
> All the best,
>
> Jools
>
>
> On Sun, 2022-02-20 at 13:01 +0100, Paul B Mahol 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
> > > > > _______________________________________________
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