I have a Raspberry on which I want to create a timelapse movie.
All examples I see in the internet FIRST save a bunch of images and THEN converts them into a movie all at once.
I want to create a movie over a long period of time so I can't save thousands of images. What I need is a tool that adds an image to a movie right after the image is captured.
Is there a chance to do that?
There's a flaw in your logic, I think - by adding each image to the movie, you would necessarily be adding a full-frame, rather than only a diff frame. This will result in higher quality, sure - but it will also not save you anything in terms of space as compared to saving the entire image. The space savings you see in adding things to movies is all about that diff, rather than storing a full frame.
Doing a partial diff with check-frames at increments might work, but I'm not sure what format you're targeting, nor what codexes would be needed in order to arbitrarily tack on either a diff frame or a full frame, depending on some external condition - encoding usually takes place as a series of operations rather than singly.