Your best bet would be to connect the output of the Video Input
patch to an Input Splitter whose type is boolean. If the sequence
grabber initialization fails, it will output nil images which are
typecast to false over the Input Splitter. Publish the output of
the splitter and use -valueForOutputKey in your code.
Thanks for the very clever suggestion! It works fine in QC, but from
my app -valueForOutputKey: seems to return before the video is quite
established, giving a false negative. Not sure how I would go about
stalling or delaying the output of a published port... Or is there
another QC way? Right now, in my app, I have to detach a thread,
sleep, and then do -valueForOutputKey: from the thread, which is
ugly, to say the least.
This call loads my .qtz video composition, and all works well
unless the iSight camera is munged. Then, it issues the "Sequence
grabber initialization failed" error message to the console. My
app doesn't seem to know the difference. In either case, it
appears that a healthy QCRenderer object is returned.
So how can my app tell if the .qtz video composition actually was
able to connect to the camera?
Is there some way I can trap this error in my QC/Cocoa video app,
so I can put up an alert panel to the user? I don't see what QC
component/call is issuing it. Is there a corresponding
notification issued that I could listen for?
Roland
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