[linux-audio-dev] Sidechains, was Re: [linux-audio-announce] [ANN] swh-plugins 0.3.4

[Robert Jonsson]

Hi,

> 
> SC4 is more-or-less like SC3, but has no sidechain and a subtly different
> algorithm. The sidechain was confusing hosts.
> 

Yes, I was wondering how the 3<-->2 port sidechain compressor plugin 
would be handled in hosts...

Sidechains are a very powerful feature however and I'd want one for sure.

I've been giving this some thinking, don't know if this has been 
discussed before... Theoretically speaking, the compressor sidechain is 
more or less just a special case for the more generic need: Audio-data 
used as control-data.

What if the sidechain was a separate ladspa plugin that in turn uses 
some ipc mechanism to communicate to the plugin being controlled?
I have no idea what kind of ipc is best for this, named pipes seem easy 
but they are probably slow, yes?
By using one of the controls of the ladspa plugin to select which 
sidechain "channel" (e.g. 1-10) they should send and receive on (much 
like a comm-radio) you could have several different sidechains up and 
running simultaneously.

This construction has a number of interesting side effects (pun not 
intended):
* 1-n setups can be produced, one sidechain can control several effects.
* Atleast with named pipes the control would be application agnostic.
   The sidechain would not need to be used in the same host as the effect
   plugin.
* I don't know if other types of plugins are applicable to this, but
   since the sidechain is a separate plugin you could make _any_ plugin
   sidechain aware. mmmm audio controlled room-size  for reverbs...mmmm
   :-D.
* Very interesting
   things can be done if other values than boolean are possible, ramps
   and what not.


Any thoughts?

mmmm... what about a sidechain that sends on several channels, but with 
some kind of arpeggio algorithm??? :-D ...I should shut up...

---

Moreover, I have only recently taking up recording......... again, after 
about two years of void (since I last used Windows for recording music), 
Ardour and MusE are getting quite usable! (now if I only could get rid 
of all those xruns :-/)
Since starting to record again I've noticed there are some specific 
plugins I'm missing that I'd like to have if anyone has got the time to 
implement them.

Top priority is a LADSPA stereo delay, I couldn't find one in Steves 
collection.
But it would also be nice with:
- stereo autopanner
- auto sweeping filters.
Apologies if these infact are available and it's just my poor eyesight.

Regards,
Robert