Do you actually know that or are you speculating?

I wouldn't be surprised if MP4 (or other video formats) provided a mechanism for tweaking the timing of a given frame. Of course, if you're using such a primitive watermark you might as well just add a note in the metadata...

Yes, I know that - I work in film and post-production for a living and I can explain the origin and workflow aspects of video frame rates to you in excruciating detail.

You know how annoying it is when you watch a movie and there's some sort of 2-dimensional 'hacker' character and s/he just says some gobbledegook about 'hacking the password' or whatever, you see something a progress bar briefly on screen, and then the actor says 'we're in!' In short, how stupid movies can be about computer topics? Well that's how it feels when someone who knows nothing about video formats or editing comes up with suggestions about adjusting the length between scenes by a few milliseconds and having it slightly different for every viewer.

This is a good time to bring up the Gell-Mann Amnesia effect(xhe).

It's where you read a page full of comments about something you really and truly deep know something about and see how very, every wrong nearly everyone is...

...then you go on to take every other page pretty seriously without remembering just how far off people were on the topic that you know about. I experienced this the other day when people were talking about beep.js on HN.

(xhe) http://www.goodreads.com/quotes/65213-briefly-stated-the-gel...

> This is a good time to bring up the Gell-Mann Amnesia effect

Thanks. Now I know the name for this.

thank you

I'm not wrong. Not because such things aren't possible (duh, we have cameras that can do varying frame rates), but because I am aware that content creators contract to deliver a product that will play back properly anywhere. Distributors' deliverables lists specify the exact frame and sample rates that they want, as opposed to what's potentially achievable within the format. Handing them something encoded with variable frame rate is going to result in automatic rejection.

Here's an example of a deliverables manual, from Netflix: http://newworlddistro.com/wp-content/uploads/2013/10/FullTec... You will get something similar from any broadcaster or video distributor. I'm not making careless extrapolations of my knowledge here, but telling you what the industry standards are. I have long involved email conversations about these things with distributors so that stuff I submit to them doesn't get sent back, triggering contractual penalty clauses for late/non-delivery that will make a producer cross with me.

But wouldn't it be trivial to notice that in the reencoding step and throw it away?

"Huh, this frame is supposed to be delayed by 3ms. Ah, screw it, [checks 'force to 23.97 fps' button]."

Yes, we know that. Video playback has physical constraints; a file format where image elements are sampled at irregular time intervals is obviously possible and useful for very "scientific" purposes like measuring when images are acquired and interpolating the raw data, but not reasonable for playing back on a screen with good compression and easy decompression.

Huh? VC-1 in WMV and H.264 in MKV both support VFR. It's not uncommon for handheld video cameras or some anime sources.

VFR exists, but would be very obvious in the metadata and would make the file unplayable on many devices.

Yeah, it's not really possible and as others have said it's by far the silliest possible way to accomplish unique file fingerprints.

its very straightforward. video comes in frames, what happens in between frames is that the same image is being displayed for that whole time. there is no way to end a scene half way through the frame - there is no visual cue or anything.

not to mention how you would go about defining the ends of scenes...

no standard format that i am aware of has variable framerate. it makes no sense.