Superimposer — combine presentation videos with slides

You have: pdf slides and a video of you talking about them.

You want: a video of your slides with you in the corner.

You need: superimposer.

So, you presented something, and now have a recording of it, that's awesome! But the slides are hard to read, or got cropped out somehow, and you want to fix that. Fear not, superimposer has you covered! Just tell it what slide to display when, point it at your slides and your video, and it will generate a new video for you with the slides front and center, and your video tucked away nicely in a corner.

To get up and running, you first need the video file for your presentation (let's say it's presentation.mp4) and a PDF file with your slides (let's say it's slides.pdf). Then, create a file called transitions.txt and write:

00:00 1

You probably get the gist here. Play through your presentation, and every time you change slides, write down a new line with the current timestamp (the O hotkey in mpv is handy here) and the desired slide number. When you're done, run:

$ superimposer presentation.mp4 slides.pdf superimposed.mp4

This will eventually kick off ffmpeg, which will take a while to encode your video. When it's done, superimposed.mp4 should have what you want!

Superimposer takes a bunch of handy command-line arguments to tweak the output. Run superimposer --help to see them. If you're using H.264, you may want to consider also giving:

-- -tune stillimage

If you are significantly resizing the camera video, you may want to change the scaling algorithm with:

-- -sws_flags lanczos

Requirements

• ffmpeg and ffprobe (usually installed with ffmpeg)
• pdftoppm (part of Poppler)

Normalizing audio

If your audio is sad, try ffmpeg-normalizer with something like:

$ ffmpeg-normalize superimposed.mp4 -o superimposed-normalized.mp4 -c:a aac

Hardware acceleration

You can pass additional parameters to the ffmpeg encoder by placing them after -- in the argument list to superimposer. You'll probably want to read up on hardware acceleration in ffmpeg, and maybe the ffmpeg VAAPI encoding docs.

Examples

Here are some examples of what the resulting video looks like: