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Comment by aw3c2 | Hacker News Reader

Yeah, that was fun:

  #starting at 467s and outputting the images of the next 3 seconds
  ffmpeg -ss 467 -t 3 -i video.mkv output.%04d.png
  # crop image to 1px slices 280 pixels from the left.
  gm mogrify -crop 1x+280+0 *.png
  # stitch them
  gm montage -border 0 -geometry +0+0 -tile x1 *.png image.jpg

Perfect example how easy and straightforward it is to use command line utilities.

Now someone just has to find movies with static camera scenes that have a lot of horizontal actor/object movement.

Random example showing Bill Bailey as a demon: http://i.imgur.com/AWWG8.jpg

Some static rallye car cameras from http://www.youtube.com/watch?v=D2QMuT04EOw -> http://i.imgur.com/GV3bY.jpg

Needs either higher framerate videos or longer scenes.

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Corollory : One could produce a whole range of image0%d.png from vertical slices through the video, and stitch them together into a movie. Essentially rotating the movie abouts its y axis (in the x-t plane).

If we assume 50fps, then every 1000px wide video would become a 3-4 minute short. But movies would require a very wide screen...

I tried that with a Super Metroid run (hoping that the results would be easier to see with a video game):

http://i.imgur.com/8TOPA.gif

Nice! That's much neater than I thought it would be.

P.S. you can use "output.%03d.png" to zero pad the output to 011 (and %04d for 0011 etc.)

Yeah, just noticed that myself. Thanks. :)

Cool demo. The 'gm montage' step isn't working for me and I'm finding its options completely non-intuitive. I produced a series of 1979 PNGs from a 66-second video, and when I stitch them with:

  gm montage -borderwidth 0 -geometry +0+0 -tile x1 *.png image.jpg

I get an image that is 45, not 1979, pixels wide. In fact the number of PNGs used as input and the resulting width have a nonlinear relationship:

    # of 1-px wide PNGs     Resulting width (px)
    5                       3
    10                      4
    20                      5
    50                      8
    100                     10
    200                     15
    500                     23
    1000                    32
    1979                    45

Note that I made a couple changes: to speed things up I used "-vf crop=1:1080:280:0" with ffmpeg to skip the separate cropping step and output 1x1080 PNGs, and my version of gm didn't accept the -border option so I assumed you meant -borderwidth.

What's up with the crazy widths on the result? What is GraphicsMagick doing?

Cool hack! I learn something new today.

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