Years ago purchased an inbetween NAV/TV Module cable for my E46. It had input / output video / audio. The audio input and output was not stereo (mono). They still sell they "ready made" on Ebay. When you buy the OEM cable it doesn't really have inputs / outputs and you would have to adjust same cable for your own use. I use the setup with my CarPC. It works OK. In this car I have all separates - TV Module, AUX module and IBUS module. Not optimal for a CarPC but more for an analogue video connection (like a DVD player-rear camera setup).

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E83 - Aero PKG Mods installed: Homelink mirror. CIS-IBUS video module, AUX, Rr Dr Release, stock wheels, Remote start, CarPC (Atom) & mud flaps - NAV - MKIV - NA Map DVD - 2011
E46 - 18.5 wheels/tires (summer), 17 stock (winter), Homelink, NAV software upgrade, BMW video module, Radio to V53, AUX, USB IBUS interface,BMW alarm install, CarPC(Epia), remote starter, tank battery & angel eyes. NAV - MKIII - NA Map CD - High Version 2008.1