Re: NullAudio example driver creates "Data Source Item 0"
Re: NullAudio example driver creates "Data Source Item 0"
- Subject: Re: NullAudio example driver creates "Data Source Item 0"
- From: Kyle Sluder <email@hidden>
- Date: Wed, 13 Mar 2013 22:01:29 -0700
And then right after you send mail to the list you take a second look at
the code and understand it better.
For some reason I thought the "data source" items should have had their
own object ID numbers. But they are not themselves objects; they are
different values for the selector property
kAudioDataSourceControlClassID in both the input and output scopes.
The "Data Source Item" prefix is actually vended by the driver. My
Cocoa-colored glasses caused me to assume the naming scheme was the
result of the System Preferences or Audio MIDI Setup interfaces using
Cocoa Bindings or cloning some NSMenuItems.
I'm still intrigued that the speaker icon and System Preferences
disagree on how to refer to the currently-selected data source.
Sorry for the noise.
--Kyle Sluder
On Wed, Mar 13, 2013, at 09:52 PM, Kyle Sluder wrote:
> I built and installed the NullAudio sample driver from
> <https://developer.apple.com/library/mac/#samplecode/UserLandDriverReference/Introduction/Intro.html>.
>
> * If I select the Null device in Audio MIDI Setup, the Source popup for
> both Input and Output gives the option of choosing from Data Source Item
> 0 through Data Source Item 4.
>
> * If I open the Sound preference pane in System Preferences, four new
> items appear on the Input and Output panes: Null and Data Source Item 0
> through Data Source Item 3.
>
> * If I option-click on the speaker icon in the menu bar, a new item
> appears: Data Source Item 0.
>
> I have two questions:
>
> 1. Why are there four items appearing in System Preferences and Audio
> MIDI Setup? Does NullAudio not sufficiently describe these items as
> input- or output-only devices? Does it not sufficiently describe them as
> stereo pairs?
>
> 2. I'm assuming the "Data Source Item" names are stemming from
> NullAudio's lack of providing names for its objects. But why does the
> name show up as Null in the Sound preference pane, but Data Source Item
> 0 in the speaker menu extra's option-click menu?
>
> --Kyle Sluder
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