The php web script that I’m using allows the admin panel to add a url, pointing to an image, that will appear as a watermark on the video when it plays on the site, but when the video is downloaded, it has no watermark (it appears). So, my question is, can the ffmpeg code be modified so that a watermark appears with the downloaded video?
Well, that means editing the video. You can do that with FFmpeg library. But, if you want the watermark to stay throughout the video, you basically have to recode the entire video. This takes a huge amount of processing and would bog down your server. Not really feasible for server usage. If these are very small video’s, you might get away with FFmpeg handling. Google FFmpeg warermarks and you can find a lot of samples.