Subject: Re: [linux-audio-dev] XAP spec - early scribbles
From: Dave Griffiths (dave@pawfal.org)
Date: Thu Feb 06 2003 - 13:18:47 EET
On Thu, 6 Feb 2003 10:40:30 +0000, Steve Harris wrote
> On Thu, Feb 06, 2003 at 01:27:39 -0500, Paul Davis wrote:
> > >Again, I think we are speaking of slightly different things. I am talking
> > >about the time when (for example) the synth at the head of the chain has
> > >stopped playing notes. A reverb with this as it's input would be told 'your
> > >input is now silent'. It has a tail, of course. It can be marked silent
> > >when it's tail is done. Once it is silent, it does not need to be
> > >processed._
> >
> > this sounds very dangerous to me.
> >
> > your description sounds OK. but ... my kawai k5000 is an additive
> > synth with a moderately interesting FX bank. its still producing sound
> > for most patches long after all of its "voices" are off. if someone
> > were to write a plugin modelled on this kind of design, you can't
> > really know when the top of the chain is silent.
>
> I agree, and more than that its not a usful optimisation (in RT
> processing), I dont htink the offline case is important enough to warrent
> this level of complexit and debugging nightmare.
>
> If you can point me to a working (not pure research) implemntation I
> will consider that it might not be total insanity ;)
I had a vague attempt at doing something like this (after noticing that
filters filtering silence uses up a lot of cpu). Each sample buffer object
that ssm uses would record whether it had been written to, and setting them to
zero (by calling memset via a Zero() function in the sample object) would
clear this flag.
In this way plugins would know whether there was any information worth
processing in the buffer. I ended up coming to the same conclusion too
complex/not enough of a win to be worth the effort.
dave
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