TroikaTronix Forum: Isadora: Bugs (Released Versions): backward speed = huge slow down


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backward speed = huge slow down

:.rux:.
Novice

Sep 24, 2007, 8:51 PM

Post #1 of 5 (2165 views)
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backward speed = huge slow down	Can't Post

i'm having a huge slow down in my system every time i play a movie in negative speed (backwards)...
i'm using both video and sound from the movie clip, a motionjpeg, 'every frame is a keyframe' .qt movie file
this is killing me..
every time i play a movie backwards my sistem slows down from 30fps to 6fps or less and starts a stuttering behaviour...

i'm still on qt 7.1.6, izzy 1.2.8
is this also happening to anyone else?
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:.rux:.
Novice

Sep 29, 2007, 12:06 PM

Post #2 of 5 (2139 views)
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Re: [:.rux:.] backward speed = huge slow down [In reply to]	Can't Post

(bump)
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Mark Coniglio
TroikaTronix / Moderator

Mar 27, 2008, 9:55 AM

Post #3 of 5 (893 views)
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Re: [:.rux:.] backward speed = huge slow down [In reply to]	Can't Post

this is MJPEG right? Not JPEG 2000?

When you say "every frame is a keyframe" that is normal for Photo JPEG, (and perhaps Motion JPEG A and Motion JPEG B too) , because each frame is compressed individually. But probably not for JPEG 2000.

Playing contemporary codecs like H264 backwards will throw the software fits, as it has to do a huge amount of work to go in that direction. (Backup, find keyframe, decompress up to the required frame, etc.) This would probably be true for _any_ codec that offers keyframes as an option.

This is why DV and Photo JPEG are superior for scrubbing and backward playing, because each frame is compressed individually.

Hope that helps,
Mark

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Mark Coniglio / TroikaTronix
Creator of Isadora

:.rux:.
Novice

Mar 27, 2008, 10:38 AM

Post #4 of 5 (891 views)
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Re: [Mark Coniglio] backward speed = huge slow down [In reply to]	Can't Post

iep, i'm using photoJpeg and motionJpeg, not h.264 nor any other mpeg..

.r
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http://www.rux-werx-here.essaycollective.org

Mark Coniglio
TroikaTronix / Moderator

Mar 27, 2008, 10:40 AM

Post #5 of 5 (890 views)
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Re: [:.rux:.] backward speed = huge slow down [In reply to]	Can't Post

and the speed is minus what? -1, -10?

Best,
Mark

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Mark Coniglio / TroikaTronix
Creator of Isadora

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