Continuing to check the high-volume limiter. Add configuration file settings for default and threshold volume settings and timeout. Include in diagnostics, set tentative defaults.

scripts/shairport-sync.conf

@@ -43,9 +43,24 @@ general =
 //		"standard" makes the volume change more quickly at lower volumes and slower at higher volumes.
 //		"flat" makes the volume change at the same rate at all volumes.
 //	volume_control_combined_hardware_priority = "no"; // when extending the volume range by combining the built-in software attenuator with the hardware mixer attenuator, set this to "yes" to reduce volume by using the hardware mixer first, then the built-in software attenuator.
+
+//	default_airplay_volume = 24.0; // this is the suggested volume after a reset or after the high_volume_threshold has been exceed and the high_volume_idle_timeout_in_minutes has passed
+
+//	The following settings are for dealing with potentially surprising high ("very loud") volume levels.
+//	When a new play session starts, it usually requests a suggested volume level from Shairport Sync. This is normally the volume level of the last session.
+//	This can cause unpleasant surprises if the last session was (a) very loud and (b) a long time ago.
+//	Thus, the user could be unpleasantly surprised by the volume level of the new session.
+
+//	To deal with this, when the last session volume is "very loud", the following two settings will lower the suggested volume after a period of idleness:
+
+//	high_threshold_airplay_volume = -16.0; // airplay volume greater or equal to this is "very loud"
+//	high_volume_idle_timeout_in_minutes = 0; // if the current volume is "very loud" and the device is not playing for more than this time, suggest the default volume for new connections instead of the current volume.
+//		Note 1: This timeout is set to 0 by default to disable this feature. Set it to some positive number, e.g. 180 to activate the feature.
+//		Note 2: Not all applications use the suggested volume: MacOS Music and Mac OS System Sounds use their own settings.
+
 //	run_this_when_volume_is_set = "/full/path/to/application/and/args"; //	Run the specified application whenever the volume control is set or changed.
 //		The desired AirPlay volume is appended to the end of the command line – leave a space if you want it treated as an extra argument.
-//		AirPlay volume goes from 0 to -30 and -144 means "mute".
+//		AirPlay volume goes from 0.0 to -30.0 and -144.0 means "mute".
 
 //	audio_backend_latency_offset_in_seconds = 0.0; // This is added to the latency requested by the player to delay or advance the output by a fixed amount.
 //		Use it, for example, to compensate for a fixed delay in the audio back end.