Subject: Re: [linux-audio-dev] TAP Scaling Limiter - how's it work?
From: Paul Winkler (pw_lists_AT_slinkp.com)
Date: Wed Feb 18 2004 - 16:17:38 EET
On Wed, Feb 18, 2004 at 08:48:02AM +0100, Tom Szilagyi wrote:
> Paul Winkler wrote:
> >ok - what happens if the input is a 30 hz sine wave?
> >assume it's coming from a particularly evil keyboard player ;-)
> >
>
> That's a particularly evil situation. :)
i know :-)
> The fact is, if you have a
> normal musical signal, it will have much higher frequency components so
> zero-crosses occur much more frequently than this limit. I investigated
> this problem a bit before i settled on that 40 Hz... a mixed signal
> (a few instruments together), or higher pitched instruments usually
> give average zero-cross frequencies of 8-12 kHz.
that high? no kidding?
> I tried it with bass
> guitar as well (real, no synth) and i didn't run into this limitation.
Unless you tried a 5-string, there's no way you'd even get a fundamental
below about 40 Hz - low E is just above 40. Low B on a 5-string
is somewhere around 30 IIRC.
Not too many instruments get below 40 Hz that I know of ... synths
and pipe organs, mostly. And they *usually* have a lot of higher
freqs mixed in.
> So if you take a 30 Hz sinusoidal from an oscillator and feed it into
> this plugin, then there will be unprocessed segments
just one, right?
> of audio because of
> not fitting in the ringbuffer.
OK. I wondered if it would try to process the last partial segment
which might get quite different scaling than the following
part of the segment when the next batch of data comes in.
> But if you really need that (do you?),
No, just satisfying my curiosity :-)
> you can increase the ringbuf size and thus decrease this freq lower
> limit in the code... at the expense of increasing latency.
That's about what I figured. Thanks!!
--Paul Winkler http://www.slinkp.com Look! Up in the sky! It's GUILDMASTER SEGWAY! (random hero from isometric.spaceninja.com)
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