The server hosting my website doesn\'t have ffmpeg and I am not allowed to install any additional extensions. Is there any other way I can make video thumbnails dynamically?
Using external service won't be feasible, since even if you find one, you'll have to PUSH whole video to it and get the thumbnail results back.
I recommend you that you host your videos somewhere where you can install ffmpeg or some other utility that will produce your thumbnails, then access (reference) whole deal from your original server location.
EDIT:
Yet another alternative is to create thumbnails on the client. Can you describe what is the way of creating and uploading videos?