[gmpi] Re: R: Re: Topic 4: Host Interface

On Fri, 28 Mar 2003, Bill Gardner wrote:

> I'm understanding correctly, a plug would communicate to the rest of the
> world in three ways: a number of synchronous pins for sample data, a number
> of asynchronous pins for events, and a direct connection to a single host
> for access to interfaces.

Yep, though it may be that synchronous pins are used for more than just
what we traditionally think of as sample data - as an example, VST2
delivers MIDI musical data events synchronously with audio data. At some
stage we will need a discussion as to which possible events belong in
which category, and why.

> For example, automation data could be events
> sent on pins (and thus plugs could be sources of automation data), or it
> could be done via an interface. One important issue is buffering, events
> can sit in buffers whereas interfaces are immediate. Another is the duplex
> issue, if you want an immediate response an interface seems to be the way
> to go. So for automation, I can imagine having both a parameter interface
> that describes parameters, converts from values to text, etc., and having
> the automation data sent to the plug via an asynchronous pin.

Sounds good. The host may often need to read state information from
plug-ins immediately, so interfaces are good for that; on the other hand,
seems like we should try to keep state transitions within the plugs
synchronous as far as possible [or at least transition requests... if the
transition is going to take a long time for the plug to accomplish, it may
have to do the work asynchronously so as not to block the
process-thread].. by keeping this synchronous you don't have to worry
so much about multithreading issues within the plugs.

Regards,
        Angus.


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