For HD videos, no. If you did not back them up to a USB storage device previously, then they are lost forever. You would have to buy them again. For SD videos, if you had copied the video to a compatible portable Playstation console such as a PSP or a Vita, then you could copy it back to the PS3 from the portable console after you restore. If you don't have the video on another console, and you didn't make a backup, then the videos are gone for good. You have to buy them again.