Just a quick command I found on stackoverflow to take a still image/thumbnail out of a video every second:
ffmpeg -i video.avi -r 0.01979 -f image2 output_%05d.jpg
Thanks to this stackoverflow post: https://stackoverflow.com/a/14710478/522859
I ran into a bit of a weird issue with a raspberry pi camera preview today. After starting the preview I hit an uncaught exception which meant that exitPreview was never called.
To get around this use the terminal hotkey and kill the python process. Note that while you won’t be able to see the terminal, it will be running in the background.
ctrl + alt + t