Digging this thread to get some info,
Does the lightning port restrict audio output to 16bit 44khz?
I.e and hi res flac will not produce 24bit output via a player through the lightning port
Not sure about the bit-depth. But I have several audio apps which do disclose the audio frequency being output (KORG iAudioGate, radius NePLAYER).
When the Apple Lightning Ear Pods (bundled with the iPhone 7+), 44.1kHz sources are output at 44.1kHz, as they should be. And sources that are at 48kHz or multiples of 48kHz, are output at 48kHz, as they should be. Using the Apple Lightning to Headphone dongle (also bundled with the iPhone 7+) gives the same results. The iPhone Control Center identifies both as "Headphones", and NePLAYER identifes the output as "Lightning".
My Sony MDR-1ADAC supposedly supports 16-bit @ 44.1kHz/48kHz through it's Lightning cable. However, no matter what the format of sound source that I play (e.g. 44.kHz source, 48kHz source, 96kHz source, DSD source, etc), the output is sent at only 44.1kHz. Even 48kHz formats, or multiples of 48kHz, are output at 44.1kHz. The iPhone Control Center identifies as "Dock", and NePLAYER identifies the output as "Other".
If I connect the MDR-1ADAC via the Apple Lighting USB 3.0 Camera Kit to the PC micro-USB connector on the MDR-1ADAC, the audio apps send the audio at their native output frequencies, as they should, BUT no actual audio is heard on the headphones - for some reason the digital audio doesn't route correctly. The iPhone Control Center identifies as "MDR-1ADAC", as it should, but again the audio doesn't actually get sent out.
I get these results on iPhone 7, iPad Air 2, and iPhone 7+, all running iOS 10.0.2 or iOS 10.0.3.
Looks like some incompatibilities - hopefully these will get corrected in future iOS updates, but I am not holding my breath on that....