AndroidMonotonicClock

Android's monotonic clock, on the exact time base AudioTimestamp.nanoTime reports: System.nanoTime(), which is CLOCK_MONOTONIC.

NOT SystemClock.elapsedRealtimeNanos(): that is CLOCK_BOOTTIME, which keeps counting while the device is in deep sleep, while CLOCK_MONOTONIC stops. The two agree until the first suspend and then sit apart by the accumulated sleep time, which can be hours. AOSP documents AudioTimestamp.nanoTime as being on the System.nanoTime() base, and the platform's own players compare it against System.nanoTime().

This pairing is the whole point of the object. The sink anchors the engine's master clock to the deadline its render callback carries, and that deadline is computed from an AudioTimestamp. Measure the rest of the engine's time from any other source and audio and video sit at a constant offset no correction can find, because both sides believe they are right. AndroidOutputBackend pairs this clock with the AudioTrack sink so the mismatch cannot be assembled, mirroring what the Apple output asserts at construction.