Media Disc Player
WARNING: This page is about a different car, the 2018 Buick Regal TourX and 2018 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
The Remote Media Player feature sends information through a USB connection to the Rear Seat Infotainment and outputs digital audio/video to vehicle displays and to the Radio over the Ethernet bus. The Rear Seat Infotainment system also has a USB hub with an auxiliary port for digital media file access.
The media disc player receives battery power and ground from the vehicle harness, and also communicates on GMLAN.