Ola ShilVin! Thanks for your answer! Like in QuickTime.. Alpha channel, it’s a extra channel which represents opacity. https://developer.apple.com/documentation/appkit/nsimagerep/1534506-alpha?language=occ https://developer.apple.com/documentation/appkit/nscolor Thanks Tom -- Sent from: http://gstreamer-devel.966125.n4.nabble.com/