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How to down-sample with motion blur 60 fps framerate to 30 fps?
  • bdegaziobdegazio

    I know this isn't specifically a GH2-related question, but I've seen a lot expertise on this forum and thought someone might know how to do this. I've searched online but can't find anything relevant.

    I've got some computer generated video at 60 fps (and higher framerates up to 120 fps) which I would like to convert to standard 30 fps, with motion blur derived from blending the intermediate frames.

    Specifically, my question is, is there an After Effects or (preferably) Apple Motion plugin that does this correctly? Or some utility software like MPEG StreamClip?

    To be clear, I don't want to change the playback speed of the video, just blend intermediate frames to simulate footage shot at a lower frame rate and corresponding shutter speed.

    thanks in advance

    bruno

    [edit] - on a hunch, I just checked the export options in StreamClip. There are "frame blending" and "better downscaling" options in the "Frame Rate" section. Does anyone have experience with using these for the purpose I described? Specifically wha's on my mind is, if downscaling a high frame rate video (e.g. 120 fps) to 30 fps, are ALL intermediate frames used in the blending? And in what proportion?

  • 10 Replies sorted by
  • yeehaanowyeehaanow

    I think the frame blending option is for slow motion. Better downscaling is for resizing. As for adding motion blur, it can be quite complicated if there are multiple objects moving in different directions. I'm not an expert on this though.

  • tidatida

    Sorry not After Effects, but this would be a simple script for AVISynth to change from 60fps to 30fps with frame blending:

    DirectShowSource("C:\....\Filename.mts")

    c1=selectevery(last, 2, 0)

    c2=selectevery(last, 2, 1)

    Overlay(c1, c2, mode="blend", opacity=0.5)

    AssumeFPS("ntsc_video")

    Or to convert from 120fps to 30fps:

    DirectShowSource("C:\....\Filename.mts")

    c1=selectevery(last, 4, 0)

    c2=selectevery(last, 4, 1)

    c3=selectevery(last, 4, 2)

    c4=selectevery(last, 4, 3)

    blend1 = Overlay(c1, c2, mode="blend", opacity=0.5)

    blend2 = Overlay(c3, c4, mode="blend", opacity=0.5)

    Overlay(blend1, blend2, mode="blend", opacity=0.5)

    AssumeFPS("ntsc_video")

  • MaxMax

    'Cc force motion blur' filter in after effects

  • yeehaanowyeehaanow

    I tried the force motion blur on some video footage at all settings. Even at the highest with a 360 shutter angle it did nothing. Maybe I was doing something wrong but I suspect it's meant for only graphics. ???

  • pdluminapdlumina

    @tida Thanks for the script. I will be trying that (probably with modifications) to see if it's possible to add some blur to 29,97 footage recorded with high shutter speed. Personally I dislike the stuttering upon playback.

  • yeehaanowyeehaanow

    I don't think you can just blend the previous frame(s) with the current frame, which is what that script looks to be doing. I think, for it to be "real" it needs to account for the vectored motion of individual objects within the frame and their speed. For example, two runners, one from the left, the other from the right, running at different speeds. There's a plugin in FCP called Stop Motion Blur that blends forward, but I've never been satisfied with it.

  • yeehaanowyeehaanow

    Check this out- There is a demo ver. http://www.revisionfx.com/products/rsmb/ Just tried it and it works. The link where I found it also suggested a Motion Vector pass out of Max as being the best option.

  • RamboRambo

    Boris BCC OFX(which i use as Vegas plugin ) has a good adaptive motion blur. I used it here on high shutter Gopro footage to blur the fast moving pixels. This was 720p50 converted to 720p25

    Even the last scene where i walk away from the camera has nice motion blur where the original was a stroby mess.

  • bdegaziobdegazio

    thanks for the links and tips. Boris and the ReelSmart both look good.

  • MaxMax

    Interpret footage in AE as 30fps, result it 2x slower, speed it up with 'stretch' and then use cc force mblur

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