Subject: Re: [linux-audio-dev] Plugin APIs (again)
From: David Olofson (david_AT_olofson.net)
Date: Sun Dec 08 2002 - 03:44:12 EET
On Sunday 08 December 2002 02.25, John Lazzaro wrote:
> > David Olofson writes:
> >
> > The point I think you're missing is that a "control change" event
> > is *exactly* the same thing as a "voice start" event on the bits
> > and bytes level.
>
> Lossy MIDI filters will prune away two MIDI Control Change commands
> in a row for the same controller value with the same data value,
> apart from controller numbers (like All Notes Off) whose semantics
> have meaning in this case. And the assumption underlying the
> behavior of these filters are present in subtle ways in other MIDI
> gear and usages too. For example, a programming language that
> presents an array with 128 members, holding the last-received (or
> default) value of each MIDI controller, presents an API that
> implicitly does this filtering, no matter how frequently the
> program samples the array.
Yes - but we're not talking about MIDI here. We *may* require that
events are never lost, and even that it's not legal to send two
identical events in line to an event port, unless you really mean
something else than to set a controller to the same value twice.
Anyway, the examples I gave in one of the other posts don't rely on
this at all. They still go by the controller *values* - for example
changes from and to 0.
The point I was trying to make was that with an event system (or a
callback system, for that matter) you don't have to constantly poll a
number of control ports to see these transitions. You only have to
check when you actually get a "change" event, since that's the only
way a control can change it's value.
//David Olofson - Programmer, Composer, Open Source Advocate
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