The device is a multi-media hub given both devices are COMPATIBLE.
IN your case your car stereo is not compatible. It was designed to work via USB with Apple products. had you had the BT option it would be working just fine.. more then likely that is.
Thru my WiFi i can go home and play music / videos / pictures via the media share app on my PS3.
I can stream music thru bluetooth, when i am in my truck i have a stereo with a 3.5mm stereo jack to plug into.
Hell its even got MHL support.
Apple products are designed to play music thru the cable because they dont use a standard micro usb pin out. They have thier own 30 or 32 or what ever number pins thier wide adapters have. This allows them to be hooked up to docking stations and charge, play, and manipulate controls via that data port. Audio is not designed on our devices to be played directly thru the micro usb port.
I would have to respectfully disagree.
My stereo is compatible with many other Android devices, including others made by Samsung. It is simply THIS phone that is not compatible. It is not the stereo lacking the capabilities, as evidenced by other Android devices playing just fine through the cable.
And Samsung should be smart enough to tailor their devices towards the market and make it compatible as such. They should not expect every other manufacturer to change their products to suit the Epic Touch 4G. Companies do this for Apple products because they dominate the market. If Samsung, or any other manufacturer, wants to compete with Apple then your products better be capable of operating in that universe and being user friendly. This is the perfect example of how Samsung has failed. Don't get me wrong...I love this phone. The stereo issue is really my only complaint. But it is a big one in my book.