It seems Apple have removed this feature on their iPhone 6S. But input gain is adjustable on other iPhone model (iPhone 4/4s/5/5s/6)
We have got confirmation from Apple’s Developer Team.
Please reference this article:
Quote from the article:
“No input gain control on 6s. Using isInputGainSettable will let you know if the input ports allow for the ability to set the input gain or not. Check, then do the appropriate thing for each case if you care to. Different hardware will always equal different capabilities over the lifetime of your application.”
We feel very sorry about this Apple’s lame decision….Hope they will give it back in iPhone 7.
As another developer said in the article:
“This sounds REALLY strange ! Starting from iPhone 4s till iPhone 6 this was available but on iPhone 6s this feature is gone ? Why is it so ????”