On Tue, Aug 13, 2019 at 15:59:39 +0200, Henning Thielemann wrote: > > "Real" watermarking should be resistent to this, upto the point that > > you need to "ruin" the video (or audio, for that matter) to get rid of > > it. > > Off topic: I always wondered how "real watermarking" is able to survive > even lossy compression, but is still invisible. Wouldn't this mean that > the lossy compression is not good enough? A compressor should be able to > eliminate the invisible artifacts for more compression gain, shouldn't it?
Interesting point. You'll actually have to dive into the research papers on the net. Obviously, those companies using watermarking have put some thought and money into this. ;-) I guess basically you find the weaknesses of the known algorithms/encoders and circumvent their strength. For example I quickly found a paper concentrating on "surviving" JPEG compression, summarizing "The result shown [sic!?] that the embedded watermark is robust to JPEG compression up to image quality 60 (~91% compressed)." Obviously, this is still/single image and not motion video in this case, but you get the point. In streams with a timescale (i.e. audio and video), you can probably do stuff like e.g. a modulated wobble in volume or brightness, which may be something the compression algorithms don't consider to "optimize" away. OTOH, you can probably craft an encoder which is specifically able to remove such watermark effects, if it knows about them. A lot of waste of engineering energy, better invested into e.g. better security or saving the planet, if you ask me. ;-) Cheers, Moritz _______________________________________________ ffmpeg-user mailing list email@example.com https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".