Move backend settings to backend stanzas

scripts/shairport-sync.conf

@@ -15,9 +15,6 @@ general =
 // resync_threshold = 2205; // a synchronisation error greater than this will cause resynchronisation; 0 disables it
 // log_verbosity = 0; // "0" means no verbosity, "3" is highest.
 // ignore_volume_control = "no"; // set this to "yes" if you want the volume to be at 100% no matter what the source's volume control is set to.
-
-// This may well change -- move it to the backend's settings... 
-// audio_backend_buffer_desired_length = 6615; // If set too small, buffer underflow occurs on low-powered machines. Too long and the response times with software mixer become annoying.
 };
 
 latencies =
@@ -51,6 +48,8 @@ alsa =
 // mixer_type = "software"; // "software" or "hardware"
 // mixer_device = "default"; //actually, the mixer default is whatever the output_device is. Normally you wouldn't have to use this.
 // mixer_control_name = "PCM"; // the name of the mixer to use -- there is no default.
+// audio_backend_latency_offset = 0; // Set this offset to compensate for a fixed delay in the audio back end. E.g. if the output device delays by 100 ms, set this to -4410.
+// audio_backend_buffer_desired_length = 6615; // If set too small, buffer underflow occurs on low-powered machines. Too long and the response times with software mixer become annoying.
 };
 
 // These are parameters for the pipe back end, an experimental back end that directs output to a pipe.