Add and use dB/linear conversion functions.

10 files changed, 40 insertions, 22 deletions

diff --git a/src/lib/audio_buffers.cc b/src/lib/audio_buffers.cc
index cceb12672..cfe762659 100644
--- a/src/lib/audio_buffers.cc
+++ b/src/lib/audio_buffers.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2017 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2020 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -18,6 +18,7 @@
 
 */
 
+#include "util.h"
 #include "audio_buffers.h"
 #include "dcpomatic_assert.h"
 #include <cassert>
@@ -309,7 +310,7 @@ AudioBuffers::accumulate_frames (AudioBuffers const * from, int32_t frames, int3
 void
 AudioBuffers::apply_gain (float dB)
 {
-	float const linear = pow (10, dB / 20);
+	float const linear = db_to_linear (dB);
 
 	for (int i = 0; i < _channels; ++i) {
 		for (int j = 0; j < _frames; ++j) {
diff --git a/src/lib/hints.cc b/src/lib/hints.cc
index 6cb037ed0..3edceeee3 100644
--- a/src/lib/hints.cc
+++ b/src/lib/hints.cc
@@ -235,7 +235,7 @@ Hints::thread ()
 
 			for (size_t i = 0; i < sample_peak.size(); ++i) {
 				float const peak = max (sample_peak[i].peak, true_peak.empty() ? 0 : true_peak[i]);
-				float const peak_dB = 20 * log10 (peak) + an->gain_correction (film->playlist ());
+				float const peak_dB = linear_to_db(peak) + an->gain_correction(film->playlist());
 				if (peak_dB > -3) {
 					ch += dcp::raw_convert<string> (short_audio_channel_name (i)) + ", ";
 				}
diff --git a/src/lib/util.cc b/src/lib/util.cc
index bbb444367..e4f552c4d 100644
--- a/src/lib/util.cc
+++ b/src/lib/util.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2019 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2020 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -1171,3 +1171,16 @@ write_swaroop_chain (shared_ptr<const dcp::CertificateChain> chain, boost::files
 }
 
 #endif
+
+double
+db_to_linear (double db)
+{
+	return pow(10, db / 20);
+}
+
+double
+linear_to_db (double linear)
+{
+	return 20 * log10(linear);
+}
+
diff --git a/src/lib/util.h b/src/lib/util.h
index c8dcb29d6..12c79ea5a 100644
--- a/src/lib/util.h
+++ b/src/lib/util.h
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2019 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2020 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -128,4 +128,7 @@ vector_to_list (std::vector<T> v)
 	return l;
 }
 
+extern double db_to_linear (double db);
+extern double linear_to_db (double linear);
+
 #endif
diff --git a/src/wx/audio_dialog.cc b/src/wx/audio_dialog.cc
index 9b3a93769..2f1f1c826 100644
--- a/src/wx/audio_dialog.cc
+++ b/src/wx/audio_dialog.cc
@@ -366,7 +366,7 @@ AudioDialog::setup_statistics ()
 	}
 
 	pair<AudioAnalysis::PeakTime, int> const peak = _analysis->overall_sample_peak ();
-	float const peak_dB = 20 * log10 (peak.first.peak) + _analysis->gain_correction (_playlist);
+	float const peak_dB = linear_to_db(peak.first.peak) + _analysis->gain_correction(_playlist);
 	_sample_peak->SetLabel (
 		wxString::Format (
 			_("Sample peak is %.2fdB at %s on %s"),
@@ -384,7 +384,7 @@ AudioDialog::setup_statistics ()
 
 	if (_analysis->overall_true_peak()) {
 		float const peak = _analysis->overall_true_peak().get();
-		float const peak_dB = 20 * log10 (peak) + _analysis->gain_correction (_playlist);
+		float const peak_dB = linear_to_db(peak) + _analysis->gain_correction(_playlist);
 
 		_true_peak->SetLabel (wxString::Format (_("True peak is %.2fdB"), peak_dB));
 
diff --git a/src/wx/audio_gain_dialog.cc b/src/wx/audio_gain_dialog.cc
index 72b3f86ca..5cd936d24 100644
--- a/src/wx/audio_gain_dialog.cc
+++ b/src/wx/audio_gain_dialog.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2014 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2014-2020 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -18,10 +18,11 @@
 
 */
 
-#include <cmath>
-#include <wx/spinctrl.h>
 #include "audio_gain_dialog.h"
 #include "wx_util.h"
+#include "lib/util.h"
+#include <cmath>
+#include <wx/spinctrl.h>
 
 AudioGainDialog::AudioGainDialog (wxWindow* parent, int c, int d, float v)
 	: TableDialog (parent, _("Channel gain"), 3, 1, true)
@@ -34,7 +35,7 @@ AudioGainDialog::AudioGainDialog (wxWindow* parent, int c, int d, float v)
 	_gain->SetDigits (1);
 	_gain->SetIncrement (0.1);
 
-	_gain->SetValue (20 * log10 (v));
+	_gain->SetValue (linear_to_db(v));
 
 	layout ();
 }
@@ -46,5 +47,5 @@ AudioGainDialog::value () const
 		return 0;
 	}
 
-	return pow (10, _gain->GetValue () / 20);
+	return db_to_linear (_gain->GetValue());
 }
diff --git a/src/wx/audio_mapping_view.cc b/src/wx/audio_mapping_view.cc
index 140f18d60..937dea558 100644
--- a/src/wx/audio_mapping_view.cc
+++ b/src/wx/audio_mapping_view.cc
@@ -308,7 +308,7 @@ AudioMappingView::paint_indicators (wxDC& dc)
 					)
 				);
 
-			float const value_dB = 20 * log10 (_map.get(y, x));
+			float const value_dB = linear_to_db(_map.get(y, x));
 			int const range = 18;
 			int height = 0;
 			if (value_dB > -range) {
@@ -504,7 +504,7 @@ AudioMappingView::full ()
 void
 AudioMappingView::minus6dB ()
 {
-	_map.set (_menu_input, _menu_output, pow (10, -6.0 / 20));
+	_map.set (_menu_input, _menu_output, db_to_linear(-6));
 	map_values_changed ();
 }
 
@@ -599,7 +599,7 @@ AudioMappingView::motion (wxMouseEvent& ev)
 					safe_output_channel_name(channels->second)
 					);
 			} else {
-				float const dB = 20 * log10 (gain);
+				float const dB = linear_to_db(gain);
 				s = wxString::Format (
 					_("Audio will be passed from %s channel %s to %s channel %s with gain %.1fdB."),
 					_from,
diff --git a/src/wx/audio_panel.cc b/src/wx/audio_panel.cc
index d6137ad9f..37d6f8bb6 100644
--- a/src/wx/audio_panel.cc
+++ b/src/wx/audio_panel.cc
@@ -381,7 +381,7 @@ AudioPanel::peak () const
 		playlist->add (_parent->film(), sel.front());
 		try {
 			shared_ptr<AudioAnalysis> analysis (new AudioAnalysis(_parent->film()->audio_analysis_path(playlist)));
-			peak_dB = 20 * log10 (analysis->overall_sample_peak().first.peak) + analysis->gain_correction(playlist);
+			peak_dB = linear_to_db(analysis->overall_sample_peak().first.peak) + analysis->gain_correction(playlist);
 		} catch (...) {
 
 		}
diff --git a/src/wx/audio_plot.cc b/src/wx/audio_plot.cc
index 3da7a50ff..0b7b29923 100644
--- a/src/wx/audio_plot.cc
+++ b/src/wx/audio_plot.cc
@@ -267,7 +267,7 @@ AudioPlot::y_for_linear (float p, Metrics const & metrics) const
 		p = 1e-4;
 	}
 
-	return metrics.height - (20 * log10(p) - _minimum) * metrics.y_scale - metrics.y_origin;
+	return metrics.height - (linear_to_db(p) - _minimum) * metrics.y_scale - metrics.y_origin;
 }
 
 void
@@ -294,7 +294,7 @@ AudioPlot::plot_peak (wxGraphicsPath& path, int channel, Metrics const & metrics
 			Point (
 				wxPoint (metrics.db_label_width + i * metrics.x_scale, y_for_linear (peak, metrics)),
 				DCPTime::from_frames (i * _analysis->samples_per_point(), _analysis->sample_rate()),
-				20 * log10(peak)
+				linear_to_db(peak)
 				)
 			);
 	}
@@ -363,7 +363,7 @@ AudioPlot::plot_rms (wxGraphicsPath& path, int channel, Metrics const & metrics)
 			Point (
 				wxPoint (metrics.db_label_width + i * metrics.x_scale, y_for_linear (p, metrics)),
 				DCPTime::from_frames (i * _analysis->samples_per_point(), _analysis->sample_rate()),
-				20 * log10(p)
+				linear_to_db(p)
 				)
 			);
 	}
@@ -397,7 +397,7 @@ AudioPlot::get_point (int channel, int point) const
 {
 	AudioPoint p = _analysis->get_point (channel, point);
 	for (int i = 0; i < AudioPoint::COUNT; ++i) {
-		p[i] *= pow (10, _gain_correction / 20);
+		p[i] *= db_to_linear(_gain_correction);
 	}
 
 	return p;
diff --git a/test/torture_test.cc b/test/torture_test.cc
index 10d343268..8bd541ad2 100644
--- a/test/torture_test.cc
+++ b/test/torture_test.cc
@@ -63,7 +63,7 @@ BOOST_AUTO_TEST_CASE (torture_test1)
 	staircase->set_position (film, DCPTime::from_frames (2000, film->audio_frame_rate()));
 	staircase->set_trim_start (ContentTime::from_frames (12, 48000));
 	staircase->set_trim_end (ContentTime::from_frames (35, 48000));
-	staircase->audio->set_gain (20 * log10(2));
+	staircase->audio->set_gain (linear_to_db(6));
 
 	/* And again at an offset of 50000 samples, trimmed both start and end, with a gain of 6dB */
 	staircase = content_factory("test/data/staircase.wav").front ();
@@ -72,7 +72,7 @@ BOOST_AUTO_TEST_CASE (torture_test1)
 	staircase->set_position (film, DCPTime::from_frames(50000, film->audio_frame_rate()));
 	staircase->set_trim_start (ContentTime::from_frames (12, 48000));
 	staircase->set_trim_end (ContentTime::from_frames (35, 48000));
-	staircase->audio->set_gain (20 * log10(2));
+	staircase->audio->set_gain (linear_to_db(6));
 
 	/* 1s of red at 5s in */
 	shared_ptr<Content> red = content_factory("test/data/flat_red.png").front ();