How does video IFE work? How does audio IFE work? How do airlines stream movies and music into their seats? How would airlines download content onto the seats? What supplies would be needed?
It is more common for airlines to make you use your own device since most already have something. American for example will make you download and use the American app and then you can watch movies using the inflight wifi for free.
Although some airlines do now offer online streaming, often by connecting to onboard WiFi, in-seat IFE is usually stored on a main system which is physically onboard the aircraft, and the videos are viewed from this main system by the passenger.