Hi, I found this old thread about watermarking. http://linux-audio.4202.n7.nabble.com/Looking-for-Audio-Watermarking-Advice… I have a potential use for watermarking that is entirely above board and completely within the realms of open source technology while also being business friendly at the same time. It's a potential solution to an AV sync issue where there are no other hardware sync solutions available (BLE, NFC, wifi, etc...) The host environment has ONLY audio and video hardware installed. In this situation it has been suggested that watermarking could allow syncing an audio track located on a mobile device with the main audio stream that is playing on speakers in the display room. Obviously the success of this solution is entirely dependant on the response of the mic->signal processing->output chain. I don't think Android devices will be viable in this situation ;-) However I thought it might be interesting for some people here as a counterpoint to the more sinister use of audio watermarking. The processing algorithm could be 100% open source. -- Patrick Shirkey Boost Hardware Ltd