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

10 Jan 2003

Sorry, replied direct to Robert, not list.

----- Forwarded message from Steve Harris &lt;S.W.Harris(a)ecs.soton.ac.uk-----

Date: Fri, 10 Jan 2003 09:25:32 +0000
From: Steve Harris &lt;S.W.Harris(a)ecs.soton.ac.uk&gt;
Subject: Re: Sidechains, was Re: [linux-audio-announce] [ANN] swh-plugins 0.3.4
To: Robert Jonsson &lt;robert.jonsson(a)dataductus.se&gt;

On Fri, Jan 10, 2003 at 09:47:26 +0100, Robert Jonsson wrote:
...
  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... 
The answer is 'badly'. ;)

...
  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? 
Pipes are non-deterministic, so banned in LADSPA. The only one thats an
option is shared memory.

...
  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. 
Its an interesting idea.

...
  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. 
The same is true of SHM, but if the hosts are not running in sample sync
all hell will break loose.

...
  * 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. 
Ahh, theres a misundersantding about what sidechains do here, they really
are just an audio stream.

...
  Any thoughts? 
Neat idea. Kinda evil though. Very tempting...

...
  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. 
What do you want from a stereo delay? There is an left-centre-right delay,
but thats actually a mono delay that takes stereo input and pans the
result. A stereo delay would be easy to implemnt, what controls do you
want?

There is an auto-phaser (sweeping allpass filter), but no auto wah
(sweeping bandpass), or auto panner, true. I tend to build things like
that out of SSM or pd. But there should be complete plugins.

- Steve