H ELECTRICITY
H04 ELECTRIC COMMUNICATION TECHNIQUE
H04N PICTORIAL COMMUNICATION, e.g. TELEVISION
H04N21/00 Selective content distribution, e.g. interactive television or video on demand [VOD]
H04N21/80 Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
H04N21/83 Generation or processing of protective or descriptive data associated with content; Content structuring
H04N21/835 Generation of protective data, e.g. certificates
H04N21/8358 involving watermark