[gmpi] Re: Reqs 3.8 Events - gesture start/end

On Tue, Dec 30, 2003 at 07:39:02PM +0100, David Olofson wrote:
> This sounds a bit related to what we eventually called "latched 
> controls" in XAP; controls that maintain values that are only 
> considered ("latched") when certain state changes occur. State 
> changes, in turn, are triggered by well defined changes in other 
> controls. For example, MIDI style NoteOn velocity would be a latched 
> control whose value is read only when the GATE control switches to 
> "on".

Right.  To explain a bit more of XAP:

Essentially every control is a continuous control.  You can send event at
any time.  However, some controls only matter at some times.

Example:
For a triangle simulator, the velocity control only matters at note-on time.
It just doesn't make sense after that.

For a violin simulator, the velocity control can vary continuously.

So the triangle would add some meta-data hint that velocity was 'latched'
(in the EE sense) at note-on.  When the note began, the velocity control
would be examined.  All other events for velocity would be dropped.

As it turns out, the only two latch-events that we could think up were
note-on and note-off.  So controls had two bits of meta-data.

>       2. Events are to take effect at the audio time
>          indicated by their timestamps. Ordering of events
>          with the same timestamp is irrelevant. Plugins
>          must act as if events with the same timestamp
>          are processed at the exact same time.

This makes sense to me.


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