Re: [ecasound] Seeing compression amount of LADSPA compressor?

From: Kai Vehmanen <kvehmanen@email-addr-hidden>
Date: Thu Mar 31 2005 - 01:02:16 EEST

Some errata to my ealier post:

On Mon, 28 Mar 2005, Kai Vehmanen wrote:

> The LADSPA compressors do not export any "current level" output parameters,
> so you cannot monitor those, but you can monitor the audio level.

I'm totally wrong here. :( For example SC4 has two output ports:
         "Amplitude (dB)" output, control, -40 to 12
         "Gain reduction (dB)" output, control, -24 to 0

> sh> ecasound -i foo.mp3 -o rtnull -evp -el:sc4,3,3,3,3,3,3 -c

I should have tested this first. It seems that current ecasound has a bug
in parsing LADSPA plugin port description which have colon chars in their
descriptions. Unfortunately SC* compressors all have these (for example
"Ratio (1:n)"), and thus ecasound interprets the number of arguments
incorrectly. This was just fixed in CVS. Proper example of SC4 use is:

sh> ecasound -i foo.mp3 -o alsa -evp -el:sc4,0,40,40,-18,3,6,6,0,0 -evp -c
ecasound> start
ecasound> cop-status

... as you can note, the 8. and 9. parameters of SC4 are updated. You can
also use the -evp operator to monitor peak-amplitudes before and after

With 'cop-set' you can modify SC4 parameters in real-time and immediately
hear the results.

But, but, for interactive use I strongly recommend using JAMin if at all
possible. It provides a nice and powerful UI with playing with the
compressor parameters.

I also recommend trying out the "-eca" compressor. It is not as flexible
as the LADSPA compressors, but requires less tweaking of parameters, and
thus suits better for ecasound-style use.

And to try all of this, a new snapshot with the LADSPA parsing fix
included is available at:

  Audio software for Linux!
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Received on Thu Mar 31 04:15:16 2005

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