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      01-20-2013, 09:12 AM   #30
jphughan
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Quote:
Originally Posted by alexwhittemore View Post
What they MIGHT be able to tell you is that most cars before late 2009/2010/2011 have a proprietary iPod (and thus iPhone) interface, where newer cars than that often work simply over USB. The short answer why is that the iTunes Music Store went fully DRM free by April '09. Before that, you couldn't play DRM'd songs via USB output, thus most cars wouldn't support it.
This isn't actually accurate. First of all, even cars that have regular USB inputs rather than a built-in dock connector cable have software that allows access to iPods/iPhones over a proprietary API since those devices don't allow you to just browse the stored media as if it were a flash drive. The "Enable disk use" option that was available on older iPods hasn't been available on newer devices for quite a while.

But the far greater misinformation in the quoted post is the claim about DRM audio output restrictions. As long as the DRMed audio files are being hosted on an Apple device authorized to play them, DRM has nothing to do with the ability to play those files on an external device, be it a car or a boombox. The reason is that the iDevice is doing the decryption and (usually) conversion to analog audio, so ANY device that accepts its audio via a headphone jack (or Bluetooth streaming, which is digital but decoded on the device) will be able to play any file on the device, regardless of encryption. If the device attaches purely via a dock connector built into the car, chances are it's outputting analog audio there too since the dock connector spec assigns pins for that function. And if it's using the dock connector's digital output (or the Lightning connector's digital output without an adapter that includes a DAC), even THEN it should be possible to play back DRMed files because here again the iDevice would be removing the encryption. When it comes to iOS devices and even the newer non-iOS devices, Apple doesn't even give third parties the ability to access files stored in the device's media library directly, never mind the ability to decrypt them externally; they simply provide an API to browse the library and control playback, and the iDevice does all of the decoding and output.

The ONLY case where DRMed songs not being playable via USB output would be true is if you put a bunch of DRMed files onto a USB flash drive (or some other device that allows mass storage access) rather than an iDevice and tried to play them directly. Or if you had your music on an older iDevice that supported direct file access and the external accessory chose to access the files that way rather than through Apple's APIs. That would indeed fail since in that scenario you don't have the iDevice decrypting them for you, but that also wouldn't apply to the vast majority of people who use iTunes and therefore most likely use a (likely more current) iDevice to play their music in their cars.

Quote:
Originally Posted by alexwhittemore View Post
The reasons you need a Y cable are touched upon above. If you REALLY want to know the gory technical details (you don't) I can write it up in a blog post and provide the link. But it really is that complicated a topic.
I'm sorry, what? I already covered the reasons a Y-cable is necessary above -- twice. It's not THAT complicated an explanation, and considering the incorrect information you posted above, maybe you should hold off offering to write blog posts and long, detailed explanations "fit for an engineer" until you've made sure you've got your facts straight.

Last edited by jphughan; 01-20-2013 at 09:33 AM.