Changes the input gain to the specified value.
- iOS 6.0+
- tvOS 9.0+
The new gain value, which must be in the range
0represents the lowest gain setting and
1represents the highest gain setting.
true if the new gain value was set successfully,
false if it was not.
Before calling this method, check the value in the
is property to make sure the input gain level is settable for the current inputs.