XML CO538 Anonymous Questions and Answers Keyword Index

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Keyword reference for video

Question 5 (2007):

Submission reference: IN1289

Just out of interest, would it be possible to write an application to convert videos into other formats using occam? Or would using various codecs and such be a pain?

I just mention this as all the apps ive seen that convert a video into dvd format seem to only use two cores at the most (on a quad core machine).

I guess that occam could do this task pretty well if it were possible?

Answer 5:

I (Fred) don't know a huge amount about video format conversion, but my understanding of things like MPEG4/AVI/etc. is that you have "key-frames", from which a number of successive frames are derived (as in, difference between individual frames, with the key-frame being a whole new frame). It should be possible to parallelise such things sensibly, either at a fairly high level by picking out N bunches of M frames and encoding those N in parallel, or at a low-level by computing the frame differences in parallel (should be possible to divide up an image fairly easily!).

As for programming in occam, you can call out to C libraries and such to get at the actual codec libraries (well, I have confidence in doing such things in Unix, don't know about Windows!). So it should be plausible to do video conversion in parallel and utilise all your cores.. Carl Ritson (now an RA in the department) did a video processing framework in occam-pi for his final-year project, which covers some relevant things, so you could try asking him :-) (C.G.Ritson@kent.ac.uk). One of the neat things here was playing multiple videos in parallel, or processing several video streams (from USB webcams), picking the stream with the most "interesting" features (motion detection), and dumping that to a viewer or encoded to a file. Unfortunately we haven't gotten around to including it in the KRoC distribution yet!

Keywords: video , application