Re: What corresponds to kAudioDevicePropertyDeviceIsRunningSomewhere in an audio driver?
Re: What corresponds to kAudioDevicePropertyDeviceIsRunningSomewhere in an audio driver?
- Subject: Re: What corresponds to kAudioDevicePropertyDeviceIsRunningSomewhere in an audio driver?
- From: Jeff Moore <email@hidden>
- Date: Tue, 27 May 2003 11:22:00 -0700
On Monday, May 26, 2003, at 01:16 PM, Sean McBride wrote:
Jeff Moore (email@hidden) wrote on Fri, 23 May 2003 16:21:54 -0700:
QT is a funny beast.
You can say that again. :)
It needs to run the audio hardware as long as
there is an open movie with a sound track around so that it's clock
can
update itself. So you would see a start, but probably not see the stop
until you close all the movies.
Actually I don't observe this at all. With PhantomAudioDriver and the
Built-in Apple driver I see start when starting a playback, and stop
when
pausing a playback. With my own driver I see start when starting a
playback, but I don't see stop at all: not after pause, not after
closing
the movie, not after quitting the app, and not after loging out.
That certainly seems odd. When I run the HAL against the built-in
hardware, a USB device or the MotU 828, I see the device's
IsRunningSomewhere status update as I expect. I also just tried the
PhantomAudioDriver and saw the behavior I expected as well, including
the notification bug.
Usually, the IsRunningSomewhere change lags the IsRunning change by a
small amount while the IOAudio Family keeps the hardware running after
the Stop call in order to play and erase the last bits of data. I see
this quite clearly in my brief testing.
I would do your testing with an app like Daisy (in
/Developer/Examples/CoreAudio/HAL/Daisy), where there is a direct
connection between hitting the buttons in the UI and the calls to the
driver.
I've just tried Daisy and, again, for PhantomAudioDriver and the
Built-in
Apple driver I see start and stop as expected. For my driver I notice
2
strange things:
1) Audio does not playback at all! (but it works in QT Player, FCP,
iTunes, etc.)
2) the Daisy UI does not update the 'file name' and other fields
after I
choose an AIFF file
Is this symptomatic of anything you've come across before? I'm
presently
gutting my driver as much as possible to make it more like
PhantomAudioDriver, but so far no luck.
I just tried out the Daisy code in the December Developer Tools
release, and it all seemed to work OK for me, including loading files.
If Daisy doesn't display the name of the file and it's vital info, that
means that Daisy had trouble loading the file in question.
--
Jeff Moore
Core Audio
Apple
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