diff --git a/gtk2_ardour/tempo_dialog.cc b/gtk2_ardour/tempo_dialog.cc index 0b570abdaa..a7a6f4ae75 100644 --- a/gtk2_ardour/tempo_dialog.cc +++ b/gtk2_ardour/tempo_dialog.cc @@ -267,39 +267,38 @@ TempoDialog::pulse_change () bool TempoDialog::tap_tempo_button_press (GdkEventButton *ev) { - gint64 now; - now = g_get_monotonic_time (); // microseconds + double t; + // Linear least-squares regression if (tapped) { - double interval, bpm; - static const double decay = 0.5; + t = 1e-6 * (g_get_monotonic_time () - first_t); // Subtract first_t to avoid precision problems - interval = (now - last_tap) * 1.0e-6; - if (interval <= 6.0) { - // <= 6 seconds (say): >= 10 bpm - if (average_interval > 0) { - if (average_interval > interval / 1.2 && average_interval < interval * 1.2) { - average_interval = interval * decay - + average_interval * (1.0-decay); - } else { - average_interval = 0; - } - } else { - average_interval = interval; - } + double n = tap_count; + sum_y += t; + sum_x += n; + sum_xy += n * t; + sum_xx += n * n; + double T = (sum_xy/n - sum_x/n * sum_y/n) / (sum_xx/n - sum_x/n * sum_x/n); - if (average_interval > 0) { - bpm = 60.0 / average_interval; - bpm_spinner.set_value (bpm); - } + if (t - last_t < T / 1.2 || t - last_t > T * 1.2) { + tapped = false; } else { - average_interval = 0; + bpm_spinner.set_value (60.0 / T); } - } else { - average_interval = 0; + } + if (!tapped) { + first_t = g_get_monotonic_time (); + t = 0.0; + sum_y = 0.0; + sum_x = 1.0; + sum_xy = 0.0; + sum_xx = 1.0; + tap_count = 1.0; + tapped = true; } - last_tap = now; + tap_count++; + last_t = t; return true; } diff --git a/gtk2_ardour/tempo_dialog.h b/gtk2_ardour/tempo_dialog.h index eda4e61f1a..06c5db196d 100644 --- a/gtk2_ardour/tempo_dialog.h +++ b/gtk2_ardour/tempo_dialog.h @@ -60,8 +60,10 @@ private: NoteTypes note_types; bool tapped; // whether the tap-tempo button has been clicked - gint64 last_tap; - double average_interval; + double sum_x, sum_xx, sum_xy, sum_y; + double tap_count; + double last_t; + gint64 first_t; Gtk::ComboBoxText pulse_selector; Gtk::Adjustment bpm_adjustment;