[linux-audio-dev] PTAF link and comments

[David Olofson]

On Saturday 08 February 2003 06.19, Tim Hockin wrote:
> > > BUT (you knew that was coming): the wrapped plugin is kind of a
> > > parameter, more than a control.  Changing the parameter can
> > > change the ENTIRE metadata of the plugin.
> > >
> > > Maybe we should formalize that?
> >
> > We could hint the Control as "will cause metadata changes!", but
> > who cares, really? Just for starters, if it's done that way,
> > hosts have to snoop any connections to such controls, or Really
> > Bad Things will happen.
>
> Which is what I originally was thinking.  How do presets work for
> wrappers? We need to make sure that these 'gestalting' controls
> always get loaded first.

Yes! Good point.


> Doesn't that violate some rule we tried
> to establish about order not mattering?

It does. *heh* The rule was about controls that may "refuse to accept" 
certain values depending on the values of other controls. The 
consensus was that control inputs are *inputs*, period. They can't 
change spontaneously, so plugins will have to deal with it internally 
- and consider *only* the values at any time; not order of changes.

Well, I guess it's ok to just hint them as "write us first!", so hosts 
know how to load presets. In fact, it's more like "write us before 
making any connections!" - because if you don't, first the plugins 
won't fit in the net description, and then any connections you manage 
to make despite that will be broken.


> Are there other repurcussions?

This isn't enough? ;-)


> > > > > The spec should not dictate ABI, either.  The ABI is an
> > > > > articat of the platform.  If my platform uses 32 registers
> > > > > to pass C function arguments, it is already binary
> > > > > imcompatible with your PC :)
> >
> > Well, all we really need is to pick the most widely supported
> > calling conventions for each platform. Is there *any* platform
> > that has relevant languages that do not support the native
> > variant of C calling conventions...? (At least, most compilers on
> > Un*x and Win32 seem to support at least two or three variants.)
>
> No, we need to go with whatever the native conventions are.  I
> think the original poin in the spec was that C++ code would use
> PTAF as extern "C". That is fine, you just need to put it in the
> header.

Yeah, that should do. Users of other languages, or wrapper authors, 
will have to know whether or not they have to do anything special to 
call C functions.


> Don't burden DSP programmers with things like ABI.

Right.


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

.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`---------------------------> http://olofson.net/audiality -'
   --- http://olofson.net --- http://www.reologica.se ---