From: Colin Fletcher <colin.m.fletcher@googlemail.com>
Date: Wed, 12 Feb 2014 21:49:00 +0000 (+0000)
Subject: Make 'Tap tempo' set the bpm to a running average
X-Git-Tag: 4.0-rc1~1601^2~631
X-Git-Url: https://git.carlh.net/gitweb/?a=commitdiff_plain;h=61d413ada423f456ad7687b2ae2d39047c7f53a6;p=ardour.git

Make 'Tap tempo' set the bpm to a running average

Keep a running average of the interval between clicks on the 'Tap tempo'
button, and use that average to set the bpm value.
---

diff --git a/gtk2_ardour/tempo_dialog.cc b/gtk2_ardour/tempo_dialog.cc
index 9173393ff5..56e375dc91 100644
--- a/gtk2_ardour/tempo_dialog.cc
+++ b/gtk2_ardour/tempo_dialog.cc
@@ -263,17 +263,28 @@ TempoDialog::tap_tempo ()
 	if (last_tap.tv_sec >= 0 || last_tap.tv_usec > 0) {
 		struct timeval diff;
 		double interval, bpm;
+		static const double decay = 0.5;
+
 		timersub (&now, &last_tap, &diff);
 		interval = diff.tv_sec + diff.tv_usec * 1.0e-6;
-	
-		bpm = 60.0 / interval;
-		if (bpm >= 20) {
+		if (interval <= 0.25) {
+			// >= 15 bpm, say
+			if (average_interval > 0) {
+				average_interval = interval * decay
+					+ average_interval * (1.0-decay);
+			} else {
+				average_interval = interval;
+			}
+
+			bpm = 60.0 / average_interval;
 			bpm_spinner.set_value (bpm);
+		} else {
+			average_interval = 0;
 		}
+	} else {
+		average_interval = 0;
 	}
 	last_tap = now;
-
-	
 }
 
 MeterDialog::MeterDialog (TempoMap& map, framepos_t frame, const string&)
diff --git a/gtk2_ardour/tempo_dialog.h b/gtk2_ardour/tempo_dialog.h
index 848b55cb59..9e97afa98d 100644
--- a/gtk2_ardour/tempo_dialog.h
+++ b/gtk2_ardour/tempo_dialog.h
@@ -58,6 +58,7 @@ private:
 	NoteTypes note_types;
 
 	struct timeval last_tap;
+	double average_interval;
 
 	Gtk::ComboBoxText pulse_selector;
 	Gtk::Adjustment   bpm_adjustment;