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Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err?

Subject: Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err?
From: Jeff Moore <email@hidden>
Date: Mon, 19 Mar 2007 14:06:55 -0700
Delivered-to: email@hidden
Delivered-to: email@hidden


On Mar 19, 2007, at 1:24 PM, Michael Dautermann wrote:

Hi Jeff, thanks for following up!
On Mar 19, 2007, at 12:45 PM, Jeff Moore wrote:
My audio plug-in should be selectable without having live audio streams (or a device connected) though, right?
Can you explain a bit more about what you mean?
I see how that's a confusing choice of words on my part.
The more succinct question I should have asked was: "if somebody in DTS were looking at my plug-in code, they should be able to select & open the plug-in via the sequence grabber even though they wouldn't have my unique device connected nor would they necessarily hear modulating audio, right?"

My plugin claims an AudioDeviceID in its Initialize function. At the same time, the plugin also claims two AudioStreamID's (one for the left and one for the right channel) and marks those two stream id's as created via AudioHardwareStreamsCreated. And it's through those id's the "DeviceGetProperty" and "StreamGetProperty" functions are presumably being called.

In this case, I would expect that applications would see a device with two streams.

You can confirm or deny this by using HALLab, which is one of the sample projects in our SDK. HALLab basically tries to be a GUI onto the raw HAL API. So, you can see all the properties and their values that your device is exposing. Often, this can expose where your API conformance is a bit lacking, so it's a good place to make sure your device is working as you expect before trying it out with the rest of the system.

If you plug-in is currently not exposing any AudioDevices, then the Sequence Grabber won't see anything. If you plug-in is exposing an AudioDevice without any AudioStreams, then I imagine that most apps would ignore your device.

If it's something else, you'll need to get into more detail about what you are doing and what you expect to see happen.
What I was expecting to happen was that the Sequence Grabber successfully selects my Audio Hardware Plugin and starts reading off the streams (at which point, I could fire up a separate pthread to start processing incoming audio data).

Or do I need to be firing some kind of "Process" (i.e. stream processing) thread (or callbacks) to stuff audio bytes into my output mBuffers even before the sequence grabber attempts to select my plug-in?

I think you need to step back and start with the basics of creating a proper HAL plug-in. It's not at all clear to me that you have done that yet. As I mentioned above, HALLab is a great way to make sure things are working in accordance to how the system expects your device to behave. HALLab also will give you a better idea about how the HAL works because it's pretty clear that you aren't too sure about that either.

Once you have something that works in HALLab, then you can expand your testing to APIs that are layered on top of the HAL, such as the Sequence Grabber.

--

Jeff Moore
Core Audio
Apple


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References:
	>what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Michael Dautermann <email@hidden>)
	>Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Brad Ford <email@hidden>)
	>Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Michael Dautermann <email@hidden>)
	>Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Jeff Moore <email@hidden>)
	>Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Michael Dautermann <email@hidden>)
	>Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Jeff Moore <email@hidden>)
	>Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Michael Dautermann <email@hidden>)
	>Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Jeff Moore <email@hidden>)
	>Re: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err? (From: Michael Dautermann <email@hidden>)

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