HLS feels like the best format to actually embed effective watermarks in. With a traditional "large-file" video format, this is non-trivial, as you need to ree

HLS feels like the best format to actually embed effective watermarks in. With a traditional "large-file" video format, this is non-trivial, as you need to reencode (or at least remux) the entire video for each user. This is not only computationally intensive, it also prevents you from hosting your videos on a CDN, increasing bandwidth costs. With a segmented format like HLS, you can just embed the watermark in a few key segments, leaving the rest of the video intact. As long as the user can't distinguish between watermarked and non-watermarked segments, you get most of the benefit at a much lower cost. Crucially, you can keep serving the non-watermarked segments off a CDN. This makes me wonder whether there are "segment-native" watermarking algorithms. The idea would be to pre-encode each segment multiple times, with each file containing a different watermark. A random variant of each segment would be chosen for each download, with the IDs of the chosen variants saved in a database. THe security of such an algorithm would rely on the combinatorial explosion resulting from the number of allowed variant combinations. For example, with just 3 variants per segment, 15 segments would give you 59 million distinct watermarks.