Hi,
Jase wrote:
> Basically I have some very quiet white / greyish noise (seems to be
> not too bad round 350Hz region) which I need to filter. I see all
> these IIR and FIR filters and they don't mean a thing to me, the other
> filters I know probably won't be what I'm after. The more noticeable
> elements seem to be mains hum (I have a spike at 60hz, and for some
> reason at 140 Hz) so mic_filter reduces it a little, but not
> sufficiently.
You're right, we should try to put some more doc about filters...
What you need is a notch (or band-stop) filter, which removes the sound
around a given freq (350Hz in your case if I understood well). There are
several implementations of this in liquidsoap and you should play a bit
to see which fits you the best. If you source is "s" you should try one
of these
filter(freq=350., q=1., mode="notch", s)
filter.iir.eq.notch(frequency=350., q=1., s)
filter.iir.resonator.bandstop(frequency=350., q=1., s)
filter.iir.butterworth.bandstop(frequency1=345., frequency2=355., s)
The q factor controls the width of the frequency band you filter around
350Hz (if q is lower, you filter more frequencies).
I hope that helps.
Cheers,
Samuel.
PS : to developers, we should check for parameters names consistency
some time ("freq" vs. "frequency", "notch" vs. "bandstop", etc.)
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