Re: AudioServerPlugin: kAudioObjectPropertyCustomPropertyInfoList
Re: AudioServerPlugin: kAudioObjectPropertyCustomPropertyInfoList
- Subject: Re: AudioServerPlugin: kAudioObjectPropertyCustomPropertyInfoList
- From: Jeff Moore <email@hidden>
- Date: Mon, 11 Nov 2013 15:29:01 -0800
Comments inline.
—
Jeff Moore
Core Audio
Apple
On Nov 11, 2013, at 7:16 AM, Bertrand Van Kempen <email@hidden> wrote:
> Hi,
>
> I have a question about kAudioObjectPropertyCustomPropertyInfoList:
>
> For string, I have to use kAudioServerPlugInCustomPropertyDataTypeCFString
> For struct/dictionary, I have to use a CFPropertyList (kAudioServerPlugInCustomPropertyDataTypeCFPropertyList)
>
> But, for simple types as uint32_t, should I also use kAudioServerPlugInCustomPropertyDataTypeCFPropertyList.
Yes. That is correct. Custom properties support just those two types.
> I noticed that when I provide mPropertyDataType = kAudioServerPlugInCustomPropertyDataTypeNone then I can pass a uint32_t data through Get/GetPropertyData.
> It works but I'm not sure it is allowed to do that; do I have to put the uint32_t data to a CFPropertyList and use kAudioServerPlugInCustomPropertyDataTypeCFPropertyList?
> If yes, what is the size I should return in GetPropertyDataSize() for a custom property (uint32_t); sizeof(CFPropertyList)?
This is an unsupported configuration. In fact, I’d call it a bug that the HAL let’s you have a property whose data type is kAudioServerPlugInCustomPropertyDataTypeNone. The intention is that the ‘None’ type is only used for qualifier data but is not meant to be used for property data. I wrote myself a bug to enforce this at some point in the future. So, I would not ship anything based on this particular mistake in the API implementation.
> Do you have a little sample which demonstrates the use of custom properties?
We do not at the moment. But I wrote a note to make sure we add something in this area to the examples.
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