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

[Julian Pilfold-Bagwell]

No worries.  I'll push it back to -40 and see how it goes.  We have a
buidling full of people today so I'll give it a go either later or
tomorrow morning.


On Mon, 2022-02-21 at 12:39 +0100, Paul B Mahol wrote:
> 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
> > > > > > _______________________________________________
> > > > > > 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".
> > 
> > _______________________________________________
> > 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".