Audio Units secrets: how to handle plugin state save/restore?

[sinosoidal]

Hi,

I'm trying to save/restore my plugin state across DAW project sessions. On my AU class that extends AUInstrumentBase I have extended the two following methods:

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OSStatus SaveState(CFPropertyListRef *outData);

OSStatus IAu::SaveState(CFPropertyListRef *outData)
{
    AUInstrumentBase::SaveState(outData);
}

OSStatus RestoreState(CFPropertyListRef *inData);

OSStatus IAu::RestoreState(CFPropertyListRef *inData)
{
    AUInstrumentBase::RestoreState(inData);
}

When I hit save, I have a call on SaveState. My internals save the plugin state in JSON. What is a CFPropertyListRef and how can I convert the JSON to this? Can I simply save binary data?

What about restore? Is it only called when SaveState actually sets anything to outData? Is there any example on how to do it? So far I have only looked onto Will Pirkle books examples.

Any tips?

Thanks!

Regards,

Nuno

[Guillaume Piolat]

You may want to look at what IPlug is doing in IPlugAU.cpp
AU will require some defined format to be validated, but you can put arbitrary binary data in it.

[sinosoidal]

Thanks for the tip! I will give a look then.

Regards

[sinosoidal]

I have gave a look to IPlugAU.cpp and couldn't find state save/restore stuff. What am I missing?

[Vokbuz]

In short, this is save and load states from IPlugAU:
https://github.com/olilarkin/wdl-ol/blo ... .cpp#L1463
https://github.com/olilarkin/wdl-ol/blo ... .cpp#L1492

CFPropertyListRef is a special virtual type describing Core Foundation containers. In AU context I haven't seen use of any other container except CFDictionaryRef.

When saving you must create dictionary and set the following keys in it:

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kAUPresetVersionKey
kAUPresetTypeKey
kAUPresetSubtypeKey
kAUPresetManufacturerKey

And save your data in kAUPresetDataKey key.

When restoring state you should check values of those keys to make sure that the data is generated by your plugin and read data from kAUPresetDataKey.

[sinosoidal]

It took me a while to digest this but it's done! Thanks for your help. Regards