Hi Chris,
I just want to add an additional level of complexity to the discussion.
If we want to add this feature to our engage player we have an
interesting problem to keep consistency. The videos with a different
playback speed have a different lenght from the original video. If I
select a different speed I have to normalize all navigation elements.
An example: if the video would be at 0:45 minutes in real time and I
decide too speed the video up now to 1.5x I would have to jump to minute
30 in the faster video. If I click on the segment/chapter that would be
at 1h I will need to jump to 0:40 in the video.
So there needs to be some JavaScript hacking for the player too, to make
sure that that everything acts like expected here.
Rüdiger
Am 21.03.2012 22:30, schrieb Christopher Brooks:
Hi Rajat,
I have been going through the project ideas of the *openCast*, and I
came across the idea of *Variable Playback Speed**. *However I have
some doubts regarding the project. Such as how are we going to reduce
the time of the playback. Are we going to increase the speed of the
playback (which I don't believe is the idea), or are we going to
remove some part of video from the original file ? Can anyone help
me. Or does anyone know how to contact the mentor.
There are two ways to do this, either increase the speed of playback,
or compress playback by removing uninteresting parts of the video
(called "video skims"). Either of these methods are interesting to me
as a feature, but require a different background.
Increasing the speed of playback would require investigating gstreamer,
specifically how gstreamer can read and write to file descriptors in
order to hook it up with the SOX project to pitch shift audio so it
doesn't sound too "chipmonky". Fairly minimal java code would need to
be written for this integration, and the majority of code would need to
be gstreamer related with a little UI work to show alternate videos.
Creating video skims is much more involved, but a much less naive
approach to speeding up playback. You can think of video skims as
similar to lossy compression for video, where duplicate frames or
frames of video that aren't important are removed. e.g. when an
instructor has written something on the board and hasn't said anything
because he is waiting for students to transcribe it, you can delete
some seconds video. You could imagine some parameters to creating skims
to determine how aggressive they might be (e.g. ignore one video feed
over another, ignore audio, etc.).
Of course, both approaches could be used together as well, to create a
lossy high speed playback.
I'm willing to mentor this project, but it does require a fair amount
of self study and self interest. It's not by any means a trivial
project, and would probably require hanging out in #gstreamer and
asking alot of questions. A background in gstreamer would be great.
Feel free to drop me a question if you have any more thoughts,
Chris
--
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Rüdiger Rolf, M.A.
Universität Osnabrück - Zentrum virtUOS
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E-Mail: [email protected]
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