ffmpeg convert 1 jpeg frame to 10 sec video
found here: https://talotics.com/post/videos/ffmpeg-add-call-to-action-image-after/
Create a 5 second video from a png as follows:
ffmpeg -loop 1 -i image.png -pix_fmt yuv420p -t 5 promo-image.mp4

This will create a video called {promo-image.mp4} from {image.png} with a duration of {5 seconds}