[linux-audio-dev] PTAF link and comments

[David Olofson]

On Monday 03 February 2003 16.42, Steve Harris wrote:
> On Mon, Feb 03, 2003 at 04:12:19 +0200, Sami P Perttu wrote:
> > I think this is bad. There should be just one process() function,
> > which could be given two gain values, one for previous output and
> > another for the plugin's own output. Plugins would do
> >
> > out[i] = previous_gain * out[i] + gain * myoutput;
>
> David is about to say non-mixing process() is a performance hack
> ;),

Well, it is for chains of inserts among other things.


> but allways using this adds too much cost to fast plugins.

Yeah, that's what I thought at first. However, if you track the 
previous_gain and gain controls, you can select between a number of 
optimized inner loops internally. What you get is basically the same 
thing as a bunch of different callbacks, except that it's not part of 
the API, and plugins can handle it any way they like.

Oh, you *do* have to check the control events for those two controls, 
of course.

That said, I still think it seems easier to just provide a few 
different callbacks of which plugin authors can pick one or more. A 
fully optimized plugin would implement all of them, but you'll get 
away with just one. It's not as flexible, but all the complexity is 
in the host SDK; all you have to do in the plugins is copy/paste some 
code. (Which I don't like of course, but really; if you want to 
optimize, there's no other way, unless source level macro abuse 
counts...)


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

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