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Re: frameimageattime returns black frame when QuickTime is busy René J . V . Bertin Thu May 05 02:00:05 2011


I've noticed something that might be related playing back movies that
refer to large Photo JPEG streams with considerable and variable
intervals between image frames. Playing back normally on OS X I get
the occasional red frame, never at the same spot. Doesn't happen in QT
for Win32, nor when I play all frames (which probably corresponds more
to your situation).

Just some thoughts/things you might try:

- Request realtime mode in your application each time you ask for a
new frame, for the expected duration of the operation. This probably
works only when the 'extraction' occurs on the same thread (which I'm
not sure about). The OS X function to look into is thread_policy_set .

- check the load average (cf. getloadavg (3))

- What happens when you do the frame extraction N times (N possibly
depending on the load average), either in consecutive calls or looping
through the movie?

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