improve timing accuracy for meter-falloff calc.

1 files changed, 13 insertions, 1 deletions

diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index 5b9d34f5e5..9f102a016a 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -759,13 +759,25 @@ void
 AudioEngine::meter_thread ()
 {
 	pthread_set_name (X_("meter"));
+	struct timeval clock1, clock2;
+	int64_t delay = 10000; /* 1/100th sec interval */
 
 	while (true) {
-		Glib::usleep (10000); /* 1/100th sec interval */
+		/* TODO use select() for sleep:
+		 * select() has a maxium delay time,
+		 * [u]sleep has a minimum delay time
+		 */
+		Glib::usleep (delay);
 		if (g_atomic_int_get(&m_meter_exit)) {
 			break;
 		}
+		gettimeofday(&clock1, NULL);
 		Metering::Meter ();
+		gettimeofday(&clock2, NULL);
+		const int64_t elapsed_time =
+		  (clock2.tv_sec-clock1.tv_sec) * 10000
+		  + (clock2.tv_usec-clock1.tv_usec);
+		delay = max((int64_t)0, 10000 - elapsed_time);
 	}
 }