Originally Posted by pfschim
Android devices use USB as the interface (along with a 3.5mm stereo input), so Android is going to have to enable what's called music streaming over USB if the platform is ever expected to be used as a semi-serious music making device. The stereo jack is typically pretty poor quality and is plagued by noise (on any device). Androids somewhat close cousin uses music streaming over USB and a kernel app called ALSA (Advanced Linux Sound Architecture), to enable high quality music functions.
iOS devices with the original 30 pin port allowed direct links to the device DAC and core software functions that enable digital recording and other useful things for musicians. Its my understanding that the new Lightning port on iP 5 does not support much of the old 30pin port functions (including music streaming over USB), nor access to the internal DAC, so it is not currently a good fit for music apps like the ones I described. That's a major reason why I don't care about the iP5.
I don't have any experience with car audio systems that is meaningful to this conversation so I can't comment on how Android works in this environment.
How it works with USB enabled car audio, stereos and active speakers. These devices play the MP3s directly from whatever is plugged into their USB port, usually it''s a USB stick. But I've found pretty much anything that uses a FAT file system that can be read by USB, should work, hard drives, Android phones, PMPs, digital cameras, etc. I've even got a really cheap USB enabled FM radio that can play music over USB from my Lenovo Android, it just looks for MP3s on the phone and plays them. The 3.5mm headphone jack is not used. That's what I understand music over USB is.
Sounds like you've got dedicated iOS devices that use the 30pin dock connector on iOS devices, apart from iPhone 5. I know Apple does a $30 adaptor, so you're supposed to be able to use your regular 30pin dock devices with the iPhone 5, but there's problems apparently. One I heard about was with BMW car audio systems not working with it.