This is just a quick blog on how you can quickly stitch together a video file of a presentation and the corresponding talk slides using Open Broadcaster Software (OBS). First time I did this I had to fiddle a little bit around, so this also serves as a mini tutorial for future me. Feel free to leave tips & tricks in the comments.
You need a video file of the presentation and a second screen. Basically what you do is:
- Use the video file as input for image & sound
- Record the second screen
- Manually click through the slides, timing their appearance
Here is the end result, before you hit “record”

Under sources you add the video file using the + sign and you add your second screen, also using the + sign. I chose “Display Screen” for the screen recording part. Then under Audio Mixer you click the cog icon and you make sure that you put the “Desktop Audio” as well as your video input on “monitor and output”. Just to be sure I muted the “Misc/Aux” audio source in the main mixer screen.

Lastly you need to play around with the input and output size under “Settings” on the right side of the OBS screen. Since I’m no expert I just chose a screensize that allowed for both inputs to be next to each other.

That’s all, you just hit record and start clicking through the slides as the video plays.