Re: AU2 - questions about presets and ClassInfo
Re: AU2 - questions about presets and ClassInfo
- Subject: Re: AU2 - questions about presets and ClassInfo
- From: Bill Stewart <email@hidden>
- Date: Wed, 02 Oct 2002 12:41:21 -0700
on 2/10/02 11:42 AM, Marc Poirier wrote:
>
Hi. I am trying to wrap my head around state and preset management in AU
>
world and have a few questions...
>
>
Is the host responsible for keeping track of and saving data of any user
>
presets, and the AU is responsible for saving its factory presets?
Yes, except that the factory presets are what ships with the AU - it is
"not" expected that these can be modified in any way, or that the AU would
need to provide a mechanism for these to be stored, etc..
>
Is it expected that factory presets can be modified?
No
>
If so, is the host responsible for saving and restoring those
>
modifications?
The host can save the state of the AU at any time, and can associate a name
with that saved state
>
If not, is it expected that a factory preset, once modified, becomes a
>
user preset?
Yes
(Think of a factory preset as a ROM and you'll get the idea)
>
In DispatchSetProperty for case kAudioUnitProperty_CurrentPreset, there is
>
a notification mechanism for when the incoming preset is a factory preset
>
(NewFactoryPresetSet is called), but not for when the incoming preset is
>
a user preset. Please discuss...
All this property sets is described in:
struct AUPreset {
SInt32 presetNumber;
CFStringRef presetName;
};
So - if you're passing in a factory preset it WILL change the state of the
AU (because it can and actually should).
If you're passing in a name for a user preset, it still can't do anything
aside from associate that name with the current state when you then save
that state (it doesn't do anything about associating the preset number in
the saved state by default)
The "name" of a user preset (and a factory preset for that matter) doesn't
really mean anything - its there to associate a state with a sensible
description of that state for the user - whether that state has been
provided by the AU (factory) and modified by the user.
Bill
>
>
Thanks,
>
Marc
>
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