Introduce an accurate version of coefficient_to_dB and use it in non speed-critical

code.  Fixes mantis 2833.


git-svn-id: svn://localhost/ardour2/branches/3.0@5565 d708f5d6-7413-0410-9779-e7cbd77b26cf

8 files changed, 19 insertions, 17 deletions

diff --git a/gtk2_ardour/automation_line.cc b/gtk2_ardour/automation_line.cc
index c404da9ac7..553c23c88e 100644
--- a/gtk2_ardour/automation_line.cc
+++ b/gtk2_ardour/automation_line.cc
@@ -668,7 +668,7 @@ AutomationLine::fraction_to_string (double fraction) const
 		if (fraction == 0.0) {
 			snprintf (buf, sizeof (buf), "-inf");
 		} else {
-			snprintf (buf, sizeof (buf), "%.1f", coefficient_to_dB (slider_position_to_gain (fraction)));
+			snprintf (buf, sizeof (buf), "%.1f", accurate_coefficient_to_dB (slider_position_to_gain (fraction)));
 		}
 	} else {
 		double dummy = 0.0;
diff --git a/gtk2_ardour/canvas-waveview.c b/gtk2_ardour/canvas-waveview.c
index aab781081d..e41fe5944f 100644
--- a/gtk2_ardour/canvas-waveview.c
+++ b/gtk2_ardour/canvas-waveview.c
@@ -646,15 +646,15 @@ gnome_canvas_waveview_ensure_cache (GnomeCanvasWaveView *waveview, gulong start_
 		for (n = 0; n < cache->data_size; ++n) {
 
 			if (buf[n].max > 0.0f) {
-				buf[n].max = alt_log_meter(coefficient_to_dB(buf[n].max));
+				buf[n].max = alt_log_meter(fast_coefficient_to_dB(buf[n].max));
 			} else if (buf[n].max < 0.0f) {
-				buf[n].max = -alt_log_meter(coefficient_to_dB(-buf[n].max));
+				buf[n].max = -alt_log_meter(fast_coefficient_to_dB(-buf[n].max));
 			}
 			
 			if (buf[n].min > 0.0f) {
-				buf[n].min = alt_log_meter(coefficient_to_dB(buf[n].min));
+				buf[n].min = alt_log_meter(fast_coefficient_to_dB(buf[n].min));
 			} else if (buf[n].min < 0.0f) {
-				buf[n].min = -alt_log_meter(coefficient_to_dB(-buf[n].min));
+				buf[n].min = -alt_log_meter(fast_coefficient_to_dB(-buf[n].min));
 			}
 		}
 	}
diff --git a/gtk2_ardour/editor_ops.cc b/gtk2_ardour/editor_ops.cc
index b9a1ffdd7e..f6d9bd7950 100644
--- a/gtk2_ardour/editor_ops.cc
+++ b/gtk2_ardour/editor_ops.cc
@@ -4730,8 +4730,6 @@ Editor::adjust_region_scale_amplitude (bool up)
 		}
 
 		fraction = slider_position_to_gain (fraction);
-		fraction = coefficient_to_dB (fraction);
-		fraction = dB_to_coefficient (fraction);
 
 		if (up && fraction >= 2.0) {
 			continue;
diff --git a/gtk2_ardour/gain_meter.cc b/gtk2_ardour/gain_meter.cc
index 40d68f551d..425929c9d2 100644
--- a/gtk2_ardour/gain_meter.cc
+++ b/gtk2_ardour/gain_meter.cc
@@ -375,17 +375,17 @@ GainMeterBase::show_gain ()
 	char buf[32];
 
 	float v = gain_adjustment.get_value();
-	
+
 	if (!_is_midi) {
 		if (v == 0.0) {
 			strcpy (buf, _("-inf"));
 		} else {
-			snprintf (buf, sizeof (buf), "%.1f", coefficient_to_dB (slider_position_to_gain (v)));
+			snprintf (buf, sizeof (buf), "%.1f", accurate_coefficient_to_dB (slider_position_to_gain (v)));
 		}
 	} else {
 		snprintf (buf, sizeof (buf), "%.1f", v);
 	}
-	
+
 	gain_display.set_text (buf);
 }
 
diff --git a/gtk2_ardour/rc_option_editor.cc b/gtk2_ardour/rc_option_editor.cc
index 9ed1a8f982..662387ef1c 100644
--- a/gtk2_ardour/rc_option_editor.cc
+++ b/gtk2_ardour/rc_option_editor.cc
@@ -803,7 +803,7 @@ public:
 			if (val == 0.0) {
 				snprintf (buf, sizeof (buf), "-inf");
 			} else {
-				snprintf (buf, sizeof (buf), "%.2f", coefficient_to_dB (val));
+				snprintf (buf, sizeof (buf), "%.2f", accurate_coefficient_to_dB (val));
 			}
 
 			_db_display.set_text (buf);
diff --git a/gtk2_ardour/route_ui.cc b/gtk2_ardour/route_ui.cc
index f0f9827b73..ad63daad5d 100644
--- a/gtk2_ardour/route_ui.cc
+++ b/gtk2_ardour/route_ui.cc
@@ -1428,23 +1428,23 @@ RouteUI::parameter_changed (string const & p)
 void
 RouteUI::step_gain_up ()
 {
-	_route->set_gain (dB_to_coefficient (coefficient_to_dB (_route->gain_control()->get_value()) + 0.1), this);
+	_route->set_gain (dB_to_coefficient (accurate_coefficient_to_dB (_route->gain_control()->get_value()) + 0.1), this);
 }
 
 void
 RouteUI::page_gain_up ()
 {
-	_route->set_gain (dB_to_coefficient (coefficient_to_dB (_route->gain_control()->get_value()) + 0.5), this);
+	_route->set_gain (dB_to_coefficient (accurate_coefficient_to_dB (_route->gain_control()->get_value()) + 0.5), this);
 }
 
 void
 RouteUI::step_gain_down ()
 {
-	_route->set_gain (dB_to_coefficient (coefficient_to_dB (_route->gain_control()->get_value()) - 0.1), this);
+	_route->set_gain (dB_to_coefficient (accurate_coefficient_to_dB (_route->gain_control()->get_value()) - 0.1), this);
 }
 
 void
 RouteUI::page_gain_down ()
 {
-	_route->set_gain (dB_to_coefficient (coefficient_to_dB (_route->gain_control()->get_value()) - 0.5), this);
+	_route->set_gain (dB_to_coefficient (accurate_coefficient_to_dB (_route->gain_control()->get_value()) - 0.5), this);
 }
diff --git a/libs/ardour/ardour/dB.h b/libs/ardour/ardour/dB.h
index 6ee6279b12..1b5bb03d1f 100644
--- a/libs/ardour/ardour/dB.h
+++ b/libs/ardour/ardour/dB.h
@@ -26,8 +26,12 @@ static inline float dB_to_coefficient (float dB) {
 	return dB > -318.8f ? pow (10.0f, dB * 0.05f) : 0.0f;
 }
 
-static inline float coefficient_to_dB (float coeff) {
+static inline float fast_coefficient_to_dB (float coeff) {
 	return 20.0f * fast_log10 (coeff);
 }
 
+static inline float accurate_coefficient_to_dB (float coeff) {
+	return 20.0f * log10 (coeff);
+}
+
 #endif /* __ardour_dB_h__ */
diff --git a/libs/ardour/meter.cc b/libs/ardour/meter.cc
index c8546c8ffa..76d2be262c 100644
--- a/libs/ardour/meter.cc
+++ b/libs/ardour/meter.cc
@@ -197,7 +197,7 @@ PeakMeter::meter ()
 		/* compute new visible value using falloff */
 
 		if (new_peak > 0.0) {
-			new_peak = coefficient_to_dB (new_peak);
+			new_peak = fast_coefficient_to_dB (new_peak);
 		} else {
 			new_peak = minus_infinity();
 		}