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Comment by bunje | Hacker News Reader

As a teacher, I'd like to use this in presentation slides, i.e. pause the output at specific times and continue only after a button is pressed. Does anyone know if there exists a tool, e.g., to automatically pause MP4 playback at specific times?

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I built exactly this in my Manim-based library, code-video-generator [1] (via the code-video-generator command and the --slides flag). It basically turns any Manim scene.wait() call into a pause that I can then advance with a clicker. I used it for this video [2], where I was recording in front of a green screen, but wanted the exact control when the animation continued. code-video-generator played the video fullscreen, which I then captured via obs [3] and used the obs display as a monitor to see if I was pointing at the right spot. Was a bit tricky to get all set up but worked pretty well.

[1] https://github.com/sleuth-io/code-video-generator [2] https://youtu.be/e21hJnB9J5k?t=44 [3] https://obsproject.com/

Don't know how user friendly you'd like this to be, but VLC has a text-based remote control interface: https://wiki.videolan.org/documentation:modules/rc/

This allows you to e.g. get the current time (get_time) and pause playback (pause). So you just have to write a small script that issues the commands the way you want and you'll be good.

if you are comfortable with LaTeX, you can use the animate package on beamer slides. It does just that, and allows both playing the animation or running it frame by frame (fwd and back).

manim works by generating a "partial movie file" for each animation, i.e. a single mp4 file for each scene.wait() call and so on. The final output just stitches these together.

I did exactly what you want using a small reveal.js plugin that parses the list of partial files generated by manim and inserts the corresponding video files into the presentation in thst order, it worked quite well. Let me know if you're interested and I'll throw it up on a GitHub gist.

If you want to stop at specified times, you could just split the video across several slides.

Or you could pause the video manually; in Keynote, press K to play/pause.

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