[linux-audio-dev] XAP and Event Outputs

David Olofson david at olofson.net
Mon Dec 9 19:40:01 UTC 2002


On Monday 09 December 2002 23.32, Steve Harris wrote:
> On Mon, Dec 09, 2002 at 10:09:18 +0100, David Olofson wrote:
> > That explicit delay element I'm talking about would probably be
> > an internal host object that's aware of the buffer size in the
> > loop it sits in, and subtracts the corresponding latency from the
> > delay parameter, so you get *exactly* the delay requested.
>
> That soundsa little too hosty for my tastes. I'l just believe you
> :)

Well, you could make it an ordinary plugin if you like - but it would 
still have to be aware of two things that only the host would worry 
about normally: buffer size, and the fact that there is a feedback 
loop at all.

Now, if they're "ordinary" plugins, what happens if the user chains 
two of them in the feedback loop? Which instance gets to compensate 
for the buffer latency, and how would the other instance know about 
it?


If you're willing to implement a host that supports feedback loops at 
all (with "small buffer partitions" and stuff), it might not matter 
much if you throw in some delay code as well. :-)


> > > My experience is that this isn't neccesary. Genrally nothing
> > > really supprising happens in fedback systems, unless the
> > > blocksize is very large.
> >
> > Well, most VST and DX hosts don't allow feedback loops at all,
> > AFAIK... I wouldn't think it's a major loss, unless you're doing
> > things that you *should* be doing on a modular synth.
>
> A modular synth is just the logical extreme of any synth system.

That was the way I was originally thinking about all this... No 
strict limits; let's see how far into the domains of "specialized" 
designs we can push it.


> Not being able to handle feedback is a serious failing, it rules
> out so many effects.

Then let's hack a host that supports feedback! (When we have a plugin 
API for it, that is... :-)

I don't see a good reason why there should be a conflict between 
*any* block/callback based plugin API and "well behaved" feedback 
loops. All you need is latency info (which is needed anyway) and some 
hacks in the host.


//David Olofson - Programmer, Composer, Open Source Advocate

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