Hey, if it works for you that’s great. I’m not surprised it does better than other sorts of compressors for some things. Nyquist comes with a compressor that’s similar to mine, but Audacity’s repackaging of Nyquist doesn’t include it (or a couple of library functions it uses).

“Click removal doesn’t really seem to work”

Well, clicks, pops, and other artifacts may sound similar but methods used to detect them can vary widely. For a microphone hitting something, I usually do a high-pass filter at around 20-50 Hz. It doesn’t get rid of the sound, but it gets rid of the peak in the waveform. For speech, I’d probably do a highpass to the whole thing. For dealing manually with big peaks, it’s pretty easy to use Audacity’s interactive envelope function to scale it way down.

“what do you mean when you say you don’t think adjust-samp works on samples”

The value passed to adjust-samp isn’t an individual sample, but part of the envelope that gets interpolated over the waveform. adjust-samp gets called once for each thousand samples.

Allen

The other thing I might do is decrease the compression ratio and attack/falloff speeds a bit. (Normalizing before compressing would help too.) That way the compression isn’t much harsher overall, but noise isn’t boosted as much.

I guess a more general solution would be to generalize the compression ratio parameter into a function with a domain of input dB and range of output dB, which is how SoundForge’s compressor works. It would probably be relatively easy to implement, but Audacity doesn’t offer a good GUI for that, or a way to create one, so you’d have to tweak the file itself every time you changed the function. The function would just replace “adjust-samp”, and look something like this, I guess:

(defun adjust-samp (db)
  (db-to-linear
    (cond
      ((< db -30) 0)
      (t db))))

“cond” is like a switch statement, with “t” being the default clause. The maximum amplitude and noise floor parameters would become superfluous. The sample function there silences everything below -30 dB and applies no change to everything else. But ideally if you graphed the “adjust-samp” function it would be continuous. I don’t think adjust-samp actually works on samples, btw.

I’m still getting lots of milage from your compressor. Thanks for the advice about changing the slider ranges; that lets me know for sure my settings are what I want them to be. I have another question about the noise floor, though — I’ve finally realized that it doesn’t behave as I had assumed. Sections of audio beneath the noise floor are still raised, just not quite as much as if you don’t set a noise floor. So if someone doesn’t speak for a couple seconds, you get a little hill of background noise in the middle of the break in speech. So I changed “(defun limit-amp (samp) (if (and (> floor 0) (> samp max-gain)) max-gain samp))” to “(defun limit-amp (samp) (if (and (> floor 0) (> samp max-gain)) 1 samp))”. This sort of does more like what I’d expect, though of course if something just barely breaks the noise floor, up it comes. But I barely read Lisp, so I still don’t know how most of the compressor works, and I thought I’d get your reaction to this, and see if you had any other thoughts.

Thanks,
Allen

;control floor “Floor” real “linear” .02 0.0 1.0

Just lower that 1.0 to .25 or some such. Be warned that any changes to the .ny file will cause Audacity to forget the saved values of all the parameters and go back to the built-in defaults.

The Mono framework should allow programs such as mine to run on a Mac. It requires the 1.9 version, though, which is still prerelease and a quite large download—95 MB or so.

I’ll look forward to your new version. From my perspective, I think an Audacity plug-in would be useful. To use a standalone tool I assume I’d need to export the audacity project to a single file and then re-import, right? Plus I use a Mac… is my sense correct that it’s hard to make C# programs run on Mac?

Thanks again,
Allen

I don’t directly control how precisely you can set that parameter. If you just type in the values into the text box I bet it will let you be as precise as you wish, up to the limits of double-precision floating point.

Incidentally, I’m about to release a new version with a new, better algorithm. I have initially written it in C# but could make it work (somewhat more slowly) in Audacity. If you have a standalone tool, would you still want the audacity plug-in? (If I don’t write a new audacity plug-in I’ll leave the old plug-in.)