[linux-audio-dev] more on XAP Virtual Voice ID system

[David Olofson]

On Tuesday 07 January 2003 10.28, Steve Harris wrote:
[...]
> > This is also for debate - David dislikes (and I agree) the notion
> > that you have to send a note-on but the plugin does not have
> > enough info to handle (for example) a velocity-mapped sampler
> > until later.  Process events in order.  So a few ideas are on the
> > table.
>
> You do have enough infomation, its just that it may be superseded
> later. Velocity can have a default.
>
> ONe great thing about this scheme is that it encourages people not
> to think of certain, arbitary parameters as instantiation
> parameters, withc are special in some way, 'cos there not.

Well, they *are* special in that they're latched only at certain 
points. The problem is that if synths cannot effectively *implement* 
it that way, it becomes the host's/sender's responsibility to know 
the difference, and make sure that these controls are handled the 
right way. And unless the host/sender can tell the synth exactly when 
to latch the values, there is no way to get this right.

What I'm saying is that synths should preferably behave is if *all* 
voice controls ever received are tracked on a per-VVID basis, so they 
can be latched as intended when the synth decides to start a physical 
voice. That way, you can play continous control data on latched 
control synths and vice versa, without nasty side effects or "smart" 
event processing in the host/sender.

Obviously, this just isn't possible if the number of VVIDs used to 
control a synth is unknown or very large. However, I don't see a 
reason why you would use many more VVIDs than there are physical 
voices, so I don't see this as a real problem.

Synths that don't allocate physical voices as soon as a VVID gets 
it's first control may have to allocate virtual voices upon 
connection, but I think that's acceptable, considering the 
alternatives.


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

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