Firstly, YouTube don't tend to support downloading videos as raw video files. So it wouldn't really make sense for YouTube to provide a signature when you're no

Firstly, YouTube don't tend to support downloading videos as raw video files. So it wouldn't really make sense for YouTube to provide a signature when you're not really supposed to be able to access a video file in the first place. This also wouldn't really work because a YouTube video isn't a single file. Videos are available in different qualities and formats. The video component tends to be separated from the audio component. If you want to combine them into a single file, you have to mux them. However, this process is not deterministic, so the resulting hash would differ depending on a multitude of factors.