The trick with OEM interfaces is designing for the lowest common denominator - most OEM CD-changer interfaces don't support text transfer, just track and disc number (some don't even support a time count). You need to provide an intuitive interface for several hundred CDs using controls and feedback designed for 6 or maybe 10 CDs. The PhatBox had a good stab at it once they added voice feedback (without that, it was just too complex), but the stagnating Rio prototype had a better go in my opinion.

You could add text transfer support for those protocols that can handle it, at the expense of much-increased complexity (almost as many interface configurations as head-units!). Of course, you are still left with designing an interface that has to seem intuitive while only having track up/down and disc selection controls (either disc up/down or direct disc selection depending on the unit).

If OEM head units could be designed with proper HDD-player integration in mind, either as a DJ or more directly connected, the interface could be made much more user-friendly, but we are slow enough embracing MP3-CDs....

When voice recognition gets added, and you can just say the artist/album/playlist, then we will have the OEM-acceptable safe HMI solution!

I wish I could refute Rob's comments about dealing with the auto industry, but in this case I may just have to take the criticism!! Obviously, I will pretend I am the exception

Nick