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.
That is not accessing QC in a thread-safe manner which is a potential
crasher. Just do [self performSelector:afterDelay:] on your app
controller object.
________________________________________________________
Pierre-Olivier Latour email@hidden
Quartz Composer Team Apple Computer, Inc.
