Allowing a user-space driver to be the default system driver

Subject: Allowing a user-space driver to be the default system driver
From: Eric Gorouben <email@hidden>
Date: Mon, 4 May 2009 23:14:50 +0200

Hi,

I've found this post from 2005 and Jeff Moore's reply that matches exactly my problem... but not the solution.

On Mar 24, 2005, at 7:40 AM, Stéphane Letz wrote:

We are developing a user-space driver (that implement the AudioHardwarePlugIn.h API). What is the right way to allow this kind of driver to be the default system output or input driver?
(When selecting our driver in AudioMidi setup as the default system output or input, this "state" is not saved, thus when opening again the AudioMidi setup, our driver does not appear as default system output or input anymore.)

Jeff's reply

You need to implement the following properties in each device:
kAudioDevicePropertyDeviceCanBeDefaultDevice = 'dflt',
// a UInt32 where 0 means that the device cannot be selected as the default
// device and 1 menas that it can. The isInput argument selects which kind
// of default device is being queried.

kAudioDevicePropertyDeviceCanBeDefaultSystemDevice = 'sflt',
// a UInt32 where 0 means that the device cannot be selected as the default
// system device and 1 menas that it can. The isInput argument selects which
// kind of default system device is being queried. Note that this property can
// only be queried for output.

In addition, the HAL shell adds other restrictions including (but not limited to) disallowing non-mixable devices as well as non-linear PCM devices.

I implement both properties, my device is mixable and linear PCM.

I can't however, select it as the default system output device in Tiger. It works perfectly in Leopard, but not in Tiger.

Sytem Prefernces sends me that error

2009-05-04 21:51:46.061 System Preferences[28053] Error !dev occurred while trying to set default sOut device to 262

which means,

kAudioHardwareBadDeviceError: The AudioDeviceID passed to the function doesn't map to a valid AudioDevice.

Is it related to the "...(but not limited to)..." above?

Does anybody have a solution?

Thanks in advance

Eric

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