Questions about digital audio output from iPhones

I was trying to figure out how Dragonfly DACs could work with the analog audio output from an iPhone; apparently, the answer is Apple's Lightning to USB Camera Kit, which allows you to output a digital audio stream to a USB DAC (please correct me if there is another way to get digital output without the Camera Kit). Does anyone know what kind of format(s) the iPhone can output this way? Can it output SPDIF, DSD or PCM? Or is it some proprietary Apple digital audio format?
I have found the adapter to work well. My DAC shows the input as 16/48.
Not 16/44?  I would have thought Redbook was possible (assuming you had it stored that way on the iPhone), but I've never seen a 16/48 PCM format. 
I have this set-up.  I don't know if it outputs SPDIF or DSD, but it definitely outputs 96.0kHz/24bit PCM to the DragonFly when using the Onkyo HF Player app, with the Hi-Rez add-on.  It might even output 192.0kHz/24bit PCM, but the DragonFly only accepts up to 96.0kHz/24bit PCM, so I don't know if it does or not.  I can play my 192.0kHz/24bit PCM files, but assume they are down coded.
 Thanks for your responses folks!  does anyone have a hypothesis on what controls the output format? Is it the format in which you store the file on your iPhone, or is there a conversion that takes place inside the iPhone so that everything is  sent out with the same format?