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Post-Production Options for Converting 30p MJPEG to 24p?
  • A lot of us are excited about MJPEG but the lack of 24p prevents us from using it on all/most/many of our projects.

    Given the new exciting possibilities w/ MJPEG (like Lpowell's recent contribution) I think it's worth starting a topic on ways to convert 30p mjpeg to 24p IN POST. (I know that this cannot be achieved with the hack (yet?)).

    Hunter Richards posted this a while back: I haven't tried his method yet, in no small part because I don't have "Shake" and it looks hard to find.

    Perhaps we should use thread as mainly for (1) listing or linking to methods of conversion and (2) examples. Also important is (3) how to get this kind of conversion to work flawlessly with types of audio recording

    Let's try to keep discussions of "why would you want to do this, etc" out of this thread unless you think there's something really important to state.
  • 7 Replies sorted by
  • Use AVCHD. It is fine.
    What software you run though. Are you looking to not change the timing of the shot: 1 second @ 30fps => 1 second @24fps (or @23,976fps) or are you looking for a mild slow motion: 1 second @ 30fps => .8 second @24fps (or @23.976fps)?
  • "Use AVCHD. It is fine."

    Guess you didn't read the last sentence of my post?

    "Are you looking to not change the timing of the shot: 1 second @ 30fps => 1 second @24fps (or @23,976fps) or are you looking for a mild slow motion: 1 second @ 30fps => .8 second @24fps (or @23.976fps)?"

    NOT slow motion. 30fps interpolated to 24fps.
  • Read it, ignored it.
    There is no good way that allows for artifact-free conversion. You may look into Kronos or Twixtor plug-ings (both are optical flow tech). Twixtor Pro (though more expensive) allows for more extensive than Kronos/Timewarp guiding the algorithm and thus helps to avoid chicken/egg problem (ie "I am not human, I am computer, is it a fence or is it a part of a part of a car?" problem)
  • If you can get to grips with it, Avisynth (I can hear the grumbling already!) is pretty good for this sort of thing.

    I occasionally edit videos for youth and community projects and they'll use anything from those little Kodak Zi8 cameras (which shoot at 29.97) to regular camcorders which will use 50i/25fps as we're in the UK.

    There are numerous filters available but I tend to use TDecimate (which is part of TIVTC) and MBlockFPS or MFlowFPS from MVTools2.

    TDecimate, when set to 5 cycles, can usually do a pretty good job of bringing 29.97 material down to 23.976 - the rounding isn't exact, which is why AssumeFPS(24000,1001) should be used afterwards to ensure an accurate frame rate. This filter is pretty fast and is usually good enough, but with excessive motion you'll see a lot of choppiness.

    MBlockFPS isn't as fast, but works much better for motion. Like most of the MVTools filters, it's motion compensated and so produces fewer artefacts. Frankly, the quality it produces rivals most encoding software suites, especially if you're doing an awkward conversion like 29.97fps to 25fps. MFlowFPS is another alternative, but I stick with BlockFPS as it seems to deliver better results.
  • 30fps conformed to 24fps actually looks pretty cool. It's basically the same look you get with the built in 80% slow-motion. It's great for music videos and montage shots!
  • @bwhitz True, but OP is looking for conversion rather than conforming.
  • This was pretty common a few years back when the 5DmkII came out as 30p-only. Converting to 24p in Shake works quite well, but was massively time-consuming from a rendering perspective - plus you can't buy a copy of Shake these days, although of course it's still around. MJPEG would be great for me, especially using the 4x3 mode for 2x anamorphics, but I can't get over the 30p hurdle.