[QLab] Update on the freeze bug--please read if you're encountering the freeze

[Christopher Ashworth]

Hi everyone,

As you'll recall, I'm trying to track down this ugly bug where QLab  
will freeze at launch when some kinds of FireWire devices are  
connected during launch.  I have not yet been able to recreate this  
bug on my development machines, despite the fact that I have obtained  
several of the devices that are causing the problems in the field.

The logs that many of you sent helped me narrow in on a single  
function call where QLab is freezing.  Basically, it is freezing when  
QLab tries to load in the Sound Cue plugin.  This happens before any  
code is executed in the plugin.  The plugin never finishes loading.

With your help I was able to narrow it that far, but I needed more  
information.

Yesterday Jesse Kriss (who helped me write the first version of QLab)  
was able to provide a lot of help on this.  Since his system is  
seeing the freeze with an Edirol FA-101, he graciously did some  
diagnostic work on it last night.  (Thanks very much Jesse.)

That information indicated that the freeze was occurring during some  
CoreAudio initialization routines.  This morning I sent a note to the  
CoreAudio mailing list, which, I'd like to note, is populated by some  
of the most responsive Apple engineers of any of the Mac developer  
mailing lists (for which I'm extremely grateful), and asked if this  
was possibly a CoreAudio bug.

Jeff Moore from Apple just wrote to say:

"It looks like somebody's user-land audio driver is attempting to  
open a component. This isn't something that the HAL does, so it  
pretty much means that it's a third party driver. You'd need to find  
out what driver it is from the user."

So the search is on.  I'll be trying to determine what third-party  
driver may be causing this.  For those of you who are seeing it, if  
you are able to send me a list of your audio drivers that could make  
this process much faster.  I'll also be examining the profiles you  
have sent me, but at first glance I'm not sure if it's possible to  
positively identify which components in the profile belong to audio  
device drivers.  (If anyone has tips on this I'm all ears.)

If this is indeed the cause of the problem, I won't be able to fix  
the bug outright since it would not be my bug.  But we could at least  
identify the culprit and try to work around it as well as notify the  
authors of the problem.

Thanks again for all your help!

Christopher