What does a DVRs “watermark” function do?
Digital watermarking provides a method to ensure that recorded video hasn’t been tampered with to make it more suitable as courtroom evidence. This is done by embedding coded data into every video frame as it is recorded. The watermark data does not interfere with the video image and is not visually detectable. However, if the video file is edited or changed in anyway, the watermark verification will indicate so. This is sometimes done by tinting the video output red upon encountering altered video. Digital watermarking is also be used to embed copyright information into commercially produced video and music files in an effort to detect and trace pirated media that is propogated via peer to peer file sharing services.