Checks if the output has been started and is active.
If the device has not been started, then 0 is returned. If the device has been started, then 1 is returned if it is currently active and 2 is returned if it is inactive (nothing is playing and BASS_CONFIG_DEV_NONSTOP is disabled).
When using multiple devices, the current thread's device setting (as set with BASS_SetDevice) determines which device this function call applies to.
On iOS, the return value may be 3 to indicate that the app's audio is currently interrupted, but only if the output was started prior to the interruption.
BASS_ChannelIsActive, BASS_Pause, BASS_Start, BASS_Stop, BASS_CONFIG_DEV_NONSTOP