[gmpi] Re: Summary 8.1: What is a parameter
- From: Marc Poirier <fipnid@xxxxxxxxx>
- To: gmpi@xxxxxxxxxxxxx
- Date: Thu, 21 Aug 2003 18:08:58 -0700 (PDT)
This seems to have good stuff describing what we think parameters are, but
also sort of some amount of jumping into answers for the forthcoming
topics, particularly the second half of your message. That's okay with
me, so long as this is those topics are still considered to be open to
discussion. Anyway, the first half or so, the stuff that just describes
what parameters are, sounds all good to me.
Marc
--- Tim Hockin wrote:
> I took the proposals for this, and tried to merge them. My own was
> longest
> and most explicit, but there was language in all three that I liked.
> Here
> is my first shot at a summary.
>
> Comments?
>
>
> 8.1: What is a Parameter?
> -------------------------
>
> A "Parameter" is an abstract way for a plugin to present some control to
> the
> host. Anything that is changeable in real-time is a Parameter. When
> the
> operation of the plugin is manipulated (by a GUI, a control surface,
> another
> plugin, etc) the change is communicated to the plugin using Parameters.
>
> Parameters have all sorts of meta-data, such as datatype, range, etc.
> This
> alone is not sufficient, however. Parameters need to be able to receive
> changes from a number of sources. Similar to Parameters, and usually
> related are Control-Inputs. Control-Inputs are where user actions are
> delivered.
>
> Every Parameter has a Control-Input, which is how Parameters get
> changed.
> Because we want to be able to connect plugins together, there must also
> exist Control-Outputs.
>
> It seems reasonable that we might want to generate very specific data
> (e.g.
> a tempo controller) or very generic data (e.g. a generic sine controller
> which can be connected to any Parameter). Therefore, it seems not
> unreasonable to have the Control-Outputs identify themselves as
> outputting
> normalized or natural data. Perhaps Control-Inputs can flag themselves
> as
> such, too.
>
> Because of the simple Control-Input model, any number of sources can
> manipulate Parameters. This includes automation playback, which is
> really
> just another event source. All Parameters can be automated.
>
> Because there are likely to be more than a single interface for a
> Parameter
> (e.g. GUI and motorized MIDI control), the current state of a Parameter
> must
> be sent to all listeners when that state changes. This may actually be
> handled by the host, rather than the plugin.
>
> Plugins may want to retain compatibility with older plugins while
> evolving.
> Parameters may be marked as hidden, so they are present, but not
> displayed
> to the user.
>
> When saving and restoring state, the majority of the state of the
> majority
> of plugins can be represented by taking a snapshot of the state of all
> Parameters. Sometimes, however, it is useful to save and restore opaque
> blobs of data (e.g. Parameters which have an ordering dependency, data
> which
> does not map well onto Parameters). Therefore, saving and restoring of
> plugin state involves Stata. Generally, a Statum will correspond to a
> Parameter, but a Statum may be also be a blob of opaque data. Not all
> Parameters will have associated Stata, and therefore will not be saved
> with
> the Plugin state.
>
>
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