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Which framerate to mix 24p and HBR25/30 footage?
  • Please help!

    I'm planning to do a comparison of various video modes and shutter speeds and I'd like in the end to export one video that mixes thge following material:

    • 24p footage @ 2fps that will be speed up 13x

    • 24p footage @ 2.5fps that will be speed up 10x

    • HBR30 footage @ 2.5fps that wil be speed up 12x

    • HBR25 footage @ 5fps that wil be speed up 5x

    How should I handle this in After Effects?


  • 4 Replies sorted by
  • You need a frame rate of 1950 fps. :)

    But seriously, I think it would be easier and more practical to speed each source up to the same frame rate. Variable frame rate video is hard to make and not very portable.

  • @balazer said: "But seriously, I think it would be easier and more practical to speed each source up to the same frame rate"

    Yes, that's what I thought, but is it possible to get one that avoids frame blending altogether?

  • Get one what? Frame rate? If you speed up to a frame rate that matches your target format, no blending will be necessary. Speed 2 fps up 15x to 30 fps. Speed 2.5 fps up 12x to 30 fps. Speed 5 fps up 6x to 30 fps. (or different factors for 25 fps, or 24 fps, or whatever your target format is)

    If you're asking how to do this in After Effects, I have no idea. The problem is that your video with a frame rate of 2 fps, for example, has an effective frame rate of 2 fps (1.844 fps, actually), but the video sequence is 23.976 fps, with 13 identical frames for each exposure. Before you can do anything useful with that 23.976-fps sequence, you need to eliminate the duplicate frames and get yourself a 1.844-fps sequence in which each frame is a different exposure. In Avisynth, that's easy: SelectEvery(13, 0). Then to speed it up to 29.970 fps, you'd do AssumeFPS("ntsc_video").

    If you want help using Avisynth to do all of this and get it into After Effects, I can walk you through it.

  • Thanks for the help @balazer. I probably wasn't all that clear, I was looking for one common base frame rate (possibly 30) to which I could speed up all videos without frame blending, but it's becoming clear that I should probably put up 3 different videos, each for every unique source frame rate, just to make sure I'm avoiding frame blending.

    But since I'm a lot more experienced in AviSynth/VirtualDub, I'm going to give it a go and see what comes out with frame rate conversion. Thanks for the tip, I'm trying so hard to jump into AE that I almost forgot how simple and predictable VDub's workflow can be.