A simple, but reasonably robust solution to the cam problem is just to screw around with black frames, that is, the frames in the middle of a fade out. Give yourself 20 places where you can insert an extra frame and choose 10 to insert, and you already given yourself 40 bits to play with.
(It's trivial to deal with the audio sync issues.)
Cams may have a lot of spatial unreliability, but they have a lot of temporal resolution.
And that's just my stupid of-the-cuff answer, which is already off to a decent start. And there are in fact purely-spatial solutions that do work, to which the temporal solutions can be added. The upshot is don't expect to beat these anytime soon. There's just too many bits to hide in, and so few bits needed for the identification.
> The upshot is don't expect to beat these anytime soon. There's just too many bits to hide in, and so few bits needed for the identification.
I agree. Some of the off the top of my head ideas that I literally just came up with now:
- if printing an image, drop a few dots in some rows (or columns); data is hidden in the pattern of dropped dots
- if printing text (as in, actual text goes to be rendered on the driver or printer firmware level, and not by the OS / text editor), slightly alter the shape of some letters (by adding or dropping a dot) to hide a pattern
- if printing an image, try to hide some data in its FFT (e.g. by adjusting differences between low frequencies and hiding a pattern there)
- if recording a video, slightly alter some otherwise stable global characteristic (like avg brightness of a bunch of consecutive frames in an animated movie)
- if recording a video, screw with timing patterns, as you mentioned
There are just so many properties, that the difficulty is probably mostly in picking something that's stable through usual transformations a document will undergo (e.g. scanning, JPG compression).
>Images can be cropped, rotated, recompressed, scaled, etc. and the digital watermark remains.
And none of those would impact the timing of black interim time lengths.
Also, this makes digimarc sound crappy (from their site):
>Facebook compresses images once they are posted, sometimes heavily, which can damage our invisible identifiers. Fortunately, there is a simple solution: if you pre-compress your images, then apply our identified, they should survive.
"And that's just my stupid of-the-cuff answer, which is already off to a decent start. And there are in fact purely-spatial solutions that do work, to which the temporal solutions can be added."
(It's trivial to deal with the audio sync issues.)
Cams may have a lot of spatial unreliability, but they have a lot of temporal resolution.
And that's just my stupid of-the-cuff answer, which is already off to a decent start. And there are in fact purely-spatial solutions that do work, to which the temporal solutions can be added. The upshot is don't expect to beat these anytime soon. There's just too many bits to hide in, and so few bits needed for the identification.