I wonder how long it'd take for Google to crack down on the system abuse.
Is it really abuse if the videos are viewable / playable? Presumably the ToS either already forbids covert channel encoding or soon will.
The process of creating and using the files is prohibitively unusable and so many better solutions exist that YT doesn't need to worry about it
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.
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.
Extending that into video files and it would likely be pretty massive, although you'd have some interesting time with youtube's compression algorithms
"compression resistant watermark" turns up some good resources for it. QR codes are another good example of noise tolerant data transmission (fun fact - having logos in a QR code isn't part of the spec, you're literally covering the QR code but the error-correction can handle it).
The best way I can describe it is that humans can still read text in compressed videos. The worse the compression/noise the larger the text needs to be, but we can still read it.
If creators start encoding their source and material into their content Google would probably be fine with that because it gives them data but also gives them context for that data.
Edit: I meant like "director's commentary" and "notes about production" type stuff like you used to see added to DVDs back in the day. Not "using youtube as my personal file storage". Why is this such an unpopular opinion?
it'd depends, as I don't think people using YT to store files would watch a lot of adds
Not true at all, lol. Google has a paid file storage solution. YouTube is for streaming video and that's the activity they expect on that platform. I couldn't imagine any service designed for one format would "probably be fine" with users encoding other files inside of that format.