Comment by pbhjpbhj
4 years ago
I'd expect you could store more data steganographically than the raw video data.
You can probably do things like add frames that can't be decoded and so are skipped by a decoder; that effectively allows arbitrary added hidden data. That's maybe cheating.
If you stipulate that you can't already have a copy of the unaltered file, and the data has to be extractable from a pixel copy of the rendered frames ... that becomes more interesting, I think.
Youtube doesn't give you the raw video back, it does transcoding to their given standard bitrates/resolution sets.
You'll notice this if someone has just uploaded a video to Youtube and the only version available for playback is some 360p/480p version for a few hours until Youtube gets around to processing higher bitrates.
So whatever you're encoding has to survive that transcode process.