This class is used by the audio engine to represent time.
- iOS 8.0+
- macOS 10.10+
- tvOS 9.0+
- watchOS 2.0+
Instances of this class are immutable.
A single moment in time may be represented in two different ways:
mach_absolute_time(), the system's basic clock. Referred to as “host time.”
Audio samples at a particular sample rate.
AVAudio instance may contain either or both representations; it might represent only a sample time, only a host time, or both.