[linux-audio-dev] New ladspa plugin - "BuzzKill" - Request For Comments

Hello,

I made a new plugin based on the cmt lib and swh libs called buzzkill.

It's a simple "reverse hard limiter" - it kills amplitudes below a certain level.

It works good for two purposes: Eliminating "noise" or "hiss" at about -50 or -47 DB, which was my intention. But it also works good put before guitar distortion (I was using the CAP libs tube amp sims) - eliminating the noise you get (I've got an accoustic-electric plugged in through a m-audio delta card hooked through jack-rack and the CAP's tube amp sim... then I had BuzzKill set at about -25 to -20).

Compilation: I just copied and modified the stereo amp from cmt to make this, I put the "identifier numbers" to 10,000 and 10,001 (i dunno whatchya call'em - each plugin's got a unique one). So, if you throw this file into the cmt libary, add it to cmt.h or cmt.cpp right, and add an "-lm" to the makefile in the right place it compiles (call it "alpha version" if you have no idea what I'm talking about).

So - the guitar usage sounds good, right? But, if you make a sound right about at the threshold (which you get a bit of, being sloppy on the fretboard and maybe a beer here or there), it cracks up a bit, sounds weird. So - rather than use a "look ahead" type algorithm like I saw i nthe limiters, I thought about something simpler to understand (at least for me).. which was having the parameters be two dB values (let's call'em i1 and i2 between friends)... then, having a linear scale from the input to the output as follows:

if input is of i1 amplitude, 0 dB is output.
If input is between i1 and i2, output is linearly scaled from 0 to i2
(let's see, i'd say output=input*(i2/i1)+i1 .. i think that's right)
If input is greater than i2, output equals input

It gives you a rough transition at input=i2 but I think it'll be "good nuf, ya, let's jam, ya know"

I dunno, that's what I was thinkin.. hey, it's simple, right? :) Oughtta be fast too.

Cheers,
Dan

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