[LAU] New stuff: zita-dpl

Fons Adriaensen fons at linuxaudio.org
Mon Dec 5 09:40:15 UTC 2011


On Mon, Dec 05, 2011 at 01:12:45AM +0100, Julien Claassen wrote:

>   Having read the description of the dpl1, I was wondering, if you might  
> consider including a LADSPA version of this. It sounds very interesting. 
> I remember, that we had a few discussions and you occasionally mentioned, 
> that you could see a few flaws in currently used limiters. I find, that 
> limiting for me too, can turn into a bit of a hassle. It will work very 
> smooth for most of the song and then distort in two or three places, 
> resulting in less limiting for the complete piece, which I suspect 
> wouldn't so easily happen with your app?

Every form of peak limiting produces distortion (almost by
definition), the question is if it remains acceptable or not.
You are right that DPL1 won't produce the amounts of distortion
that you would have with e.g. a scaling limiter - it really tries
to remain linear in the short term, and gain changes are always
smooth even if they can be quite fast.

The way it is intended to be used (at least on a mix) is to limit
occasional short peaks (which can be done without too much impact
on the sound) so as to allow a higher average level. If you drive
it so the limiting is active all the time (which can be done with
DPL1), little more is gained in terms of loudness, and whatever 
remains as dynamics is then controlled by peak sample levels which
in almost all cases produces something horrible.

So you need to monitor what it is doing, and that's one reason 
why DPL1 has the type of display it has, and why it is not a
Ladspa plugin. 

A second one is that I wrote this to have a limiter that can be
used on multichannel (mainly AMB here) mixes. Since Ladspa has
no 'create-time' parameters, this would require a different
plugin for each channel count. 
 
I could make mono and stereo Ladspa versions, but then they
would either require some way to monitor the gain reduction
(which can't be reduced to some slow-changing number easily),
or you'd need careful control of the input level. So that
leads to my question: how do you monitor levels ?

Ciao,

-- 
FA

Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.



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