Re: User-land CoreAudio driver and Leopard
Re: User-land CoreAudio driver and Leopard
- Subject: Re: User-land CoreAudio driver and Leopard
- From: Stéphane Letz <email@hidden>
- Date: Thu, 15 Nov 2007 21:53:39 +0100
On Nov 14, 2007, at 12:37 PM, Stéphane Letz wrote:
You need to make your device disappear from the device list in this
case using the standard methods available to you. If the device
can't
be used, it should not be presented to the user. When the server
gets
relaunched, then you can make your device re-appear on the system.
Actually I'm not even speaking of trying to update a device list for
a given application *while* the applications is running!
Let me explain in another way with teh following sequence of actions:
- start the jack server:
- open AMS, or Sound Preferences (or HALLab)
- since our jack server is running, the JackRouter plug-in will see
that and thus appears as an available device for the application.
- select JackRouter as the default input/output
- quits AMS:
So you have a happy functioning device at this point that has been set
as the default device.
- stops jack server
At this point, the device ceases to be happy or functioning. Any
currently running app should be told that the device has died and it
should be removed from the device list.
- open AMS: AMS tries to "restore" JackRouter as the defaut input/
output,
As I said in one of the previous emails, coreaudiod is where the
default device is tracked. AMS just reports what the server says.
but since the jack server does not run, the JackRouter plug-in
throw this kAudioHardwareIllegalOperationError and thus is not
available as a possible device
Ah. The problem here is that you are showing a non-functioning device
in the first place. You should just not be presenting it to the
system. It should not be in the device list, period.
- AMS does display the list correctly: the list is even completely
unsable (grayed)
Since this is the responsability of AMS to access the device list
and display correctly, what can be done?
No, it is your plug-in that is in the wrong here. AMS is just showing
what you are telling it. Your plug-in is presenting a non-functioning
device to the system. It should not be doing this.
--
OK.
So I implemented a start/stop notification mechanism based on
CFNotificationCenterPostNotification/CFNotificationCenterAddObserver
(CFNotificationCenter.h)
so that the jack server notify the JackRouter plugin.
- in the JackRouter I guess the plugin constructor is called once
when the application is loaded
- the created plugin object is kept in a static global variable so that:
- if a "stop" notification is received from the jacks server, the
instance can be used to call the "Teardown" method (so that the
plugin is removed for the application)
- if a "start" notification is received later on from the jacks
server, the global instance can be used to call the "Initialize"
method (so that the plugin appear again for the application)
This work more or less, but:
- it seems the insteraction with "coreaudiod" does not always work
(thus this incorrect displayed device list remains..)
- and sometimes it crash in the "Teardown" or "Initialize" method
Is there a better way for the start/stop notification called in the
pluging to remove/restore the plugin?
Thanks
Stephane Letz
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