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      01-21-2013, 03:41 PM   #33
alexwhittemore
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Quote:
Originally Posted by jphughan View Post
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.
There's nothing proprietary about what's happening either over the USB-only connection or the BMW Y cable. If the connection is USB (normal apple USB-Lightning or USB-30pin) the car is employing the USB Audio Class (http://www.usb.org/developers/devclass_docs/audio10.pdf). If you're using the Y cable (in the case of BMW, lots of other cars have their own connector for adapters to third-party connectors like the 30pin, for example, the Golf and GTI), the car is using the iPod Accessory Protocol on the RS232 pins of the 30pin connector to control play (send play/pause/skip/etc commands, receive data about current song, playlist, library, etc). As far as I'm aware, no car with an 'iPod' interface has ever used disk mode (i.e. accessing the raw library data via the Mass Storage Class), and I'm not even sure it'd work. Would be an interestring experiment, though, maybe it would.

Quote:
Originally Posted by jphughan View Post
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.
It does ONLY in the case of USB Audio Class output. Because the output format in that case is digital (running over USB) and unencrypted (you seem to be confusing encryption and encoding, they're quite different), it violates the terms of the licensing agreements that cover DRM. In theory, you could build a USB Audio Class host device which could copy the exact digital original of a previously DRM'd song played by an iPod, which is exactly the vector DRM tries to curtail.

Quote:
Originally Posted by jphughan View Post
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.
Some of this is true, some isn't. The iDevice WOULD BE (IS) doing the decryption/DRM removal. Since apple doesn't license FairPlay to third parties under any circumstances, BMW definitely couldn't license it and do the De-DRM in-headunit. Of course, that's only assuming USB Audio Class supports encrypted (DRM'd) transfer, which it doesn't. There's the problem. Apple isn't allowed to (wasn't allowed to then, presumably is now considering they'll let you get updated DRM-free copies of your previously-protected content) decrypt a song then transmit it digitally under any circumstance, so USB Audio Class would have been out.

Now, you're totally RIGHT about the dock connector being analog (or at least, having an analog line out, and the lightning adaptor having a built-in DAC). That's EXACTLY why the Y cable and other manufacturers' proprietary cables USE the dock connector, but DON'T support a pure USB solution. In DRM parlance, this is referred to as the Analog Hole (or A-Hole, if you're generally opposed to DRM). This is, fundamentally, why DRM was always a broken and stupid system to begin with. Sure, you couldn't make a perfect digital copy of the original, but you COULD ALWAYS make one of perfectly equivalent analog fidelity.

Quote:
Originally Posted by jphughan View Post
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.
By that which I've just responded to, the Y cable shouldn't be necessary at all, nor should it ever have been so long as iDevices supported USB Audio Class (which they have for a surprisingly long time), so I'm not sure I follow your logic. Anyway, read the USB Audio Class spec document I posted a link to above, then design me a functional Y cable (no buying online, that's cheating!), and let me know if you still think it's not complicated.

Quote:
Originally Posted by Bulldog_335xi View Post
My iPhone 5 works fine with the USB cable. All the same functionalities as with the previous 4. However now and then it will only play music on the phone despite still controlling with the idrive. I just restart the phone and it works again.
You have a newer model car with a combox.
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