[gmpi] 8a.0 What is a Parameter?
- From: Mike Berry <mberry@xxxxxxxxx>
- To: gmpi@xxxxxxxxxxxxx
- Date: Thu, 07 Aug 2003 13:54:10 -0600
From Tim:
8a.0) Define "parameter".
In XAP we called these 'controls'. My spin (off the top of my head):
* A parameter is an explicity exported representation of some variable(s)
inside a plugin.
* Parameters may represent things like knobs on hardware, plugs in a CV
module, coefficients of algorithms, or more abstract values like tempo or
MIDI controllers.
* The set of exported parameters are a snapshot of the current state of a
plugin.
* Saving and restoring a full set of parameters is sufficient to resotre the
state of a plugin 'patch'.
This can work if one of the parameter types is arbitrary data (this is a
term that Premiere and AfterEffects use in their API's). Basically, in
addition to the host-intelligible parameters, a plugin can have arb data
parameters, which is basically an opaque chunk. VST has a variation on
this with its getChunk and setChunk functions, but they are split off
from being parameters, and therefore cannot change over time. This can
actually be a very powerful mechanism, because it means that plugins are
not limited to the data types that GMPI provides. This can allow us to
keep the data type list short. For example, lets say a plugin has a
user-editable frequency representation using an FFT. Rather than expose
1024 float parameters for bin volume, which would be unuseable in a host
expecting 10 parameters or so, the plugin exposes 1 arb data parameter.
These can only be set using UI that the plugin provides, but it means
that the host can still automate the fft shape without knowing anything
about it.
* Parameters must be independant of each other.
Is this necessary? I'm not sure that it is.
* Parameters can change in real-time.
I would add:
--
Mike Berry
Adobe Systems
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