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CPU load problem and QuickTime when
Authored by: TvE on Jan 29, '03 05:20:44AM

I just posted this problem to the QT-Talk mailing list - the answer is VERY interesting - I hope that they'll soon get that bug fixed:
I have noticed something very odd:

I have some mpeg-1's that I am playing on my 867 MHzTiBook w. 768 MB RAM
running the latest OS X+QT.
My (PAL) TV is connected to the S-VHS output I am not using mirrored
display.
I am using QT player to play the movie.

If I display the movie NORMALLY (meaning NOT full screen) on either of the
displays the movie plays just fine at 25 fps and my CPU is being used
35-50%. Same thing if i display the movie in double size.

If I display the movie FULL SCREEN on either of the displays the movie plays
at a lower frame rate (because) the CPU load is maxed out at 98-100%!

I can't figure out why - the movie is displayed at exaclty the same size -
only difference is that QTP has to NOT display it's GUI - one should think
that that would put a smaller load on the CPU

Why???
Is it a bug?
Is there a workaround?
Is there an explanation?

- TvE


********Answer**************'
This is a long-standing bug, we're aware of it, and there is currently
no workaround. The explanation is long and gory, and has to do with
history--most of the full screen code was highly optimized to past
machines and operating systems (think system 7). In those days you had
to use some tricks to coax movies into playing full screen without
dropping frames. As it turns out, these same tricks on modern
preemptive multitasking operating systems can actually degrade
performance (certain demanding decodes are more affected by this).
Recent full screen enhancements have yielded some great improvements in
full screen playback (including new features), but not in CPU pegging.
I cannot comment on unreleased products, but suffice to say that the
shipping QuickTime Player's CPU overburdening really bothers us too.
One might imagine we would want to address this in the future.

Brad Ford
QuickTime Engineering



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