[linux-audio-dev] XAP spec - early scribbles

[torbenh at gmx.de]

On Thu, Feb 06, 2003 at 10:38:22AM +0000, Steve Harris wrote:
> On Wed, Feb 05, 2003 at 02:41:44 -0800, Tim Hockin wrote:
> > > Nice. Can be used for "optimized silence", of course - which leads to 
> > > a question: How about *outputs*? Plugins that keep track of whether 
> > > or not they're actually generating audio would need a way to mark 
> > > each output as "audible" or "silent", before returning from each 
> > > process/run() call.
> > 
> > Yes - we have a few options here.  This is something that can save MASSIVE
> > CPU, and is really needed.
> 
> This souds like a really bad idea, I think the intention of the plugin
> reporting its RT60 (or whatever) tail size is for post roll, not silence
> detection. Silence detection is pretty pointless in RT systems, and likly
> to a huge source of bugs.

But silence detection before some delays can be ok.

> 
> You cant use the "free" cycles, because youre never sure when the plugin
> is going to wake up and start chewing CPU again, and in any case you dont
> know how much it was really using.

the free cycles can be used for faster GUI updates. i think it is useful.

> Ontop of that the RT60 time is only a guideline, depending on the
> processing graph it may be totally inapropraite to assert silence after
> the nominal decay time.

A Delay or similar would never emit silent buffers.

>  
> > If a chain of plugins starts with a voiced instrument, we have a clue when
> > there is nothing coming down the chain (instruments need to confirm it, of
> > course).  Each plugin in the chain might eventually be silent, with silent
> > input.  Silence needs no processing.
> 
> "Silence" is relative. A reverb will onyl decay to mathematic silence
> after a really long time, but that isnt the intention of this hint IMNSHO.

Silence should be a hint on the buffer, and a Delay would only emit a silent
Buffer after being instantiated and not having input.
which in fact means never :)

-- 
torben Hohn
http://galan.sourceforge.net -- The graphical Audio language