add fall-off

4 files changed, 61 insertions, 9 deletions

diff --git a/src/lib/level_calculator.cc b/src/lib/level_calculator.cc
index 0563d4ed8..8ec5684f2 100644
--- a/src/lib/level_calculator.cc
+++ b/src/lib/level_calculator.cc
@@ -28,11 +28,10 @@ using std::shared_ptr;
 using boost::optional;
 
 
-constexpr int frames_per_measurement = 48000 / 30;
-
-
-LevelCalculator::LevelCalculator()
-	: _enabled(false)
+LevelCalculator::LevelCalculator(int calculation_frame_rate, int falloff)
+	: _calculation_frame_rate(calculation_frame_rate)
+	, _falloff_linear(pow(10, -falloff / (calculation_frame_rate * 20.0f)))
+	, _enabled(false)
 {
 
 }
@@ -42,10 +41,11 @@ void
 LevelCalculator::put(shared_ptr<const AudioBuffers> audio, dcpomatic::DCPTime time, int frame_rate)
 {
 	if (!_enabled) {
-		std::cout << "no calcs for me.\n";
 		return;
 	}
 
+	int const frames_per_measurement = frame_rate / _calculation_frame_rate;
+
 	boost::mutex::scoped_lock lm(_current_mutex);
 
 	auto const channels = audio->channels();
@@ -65,9 +65,11 @@ LevelCalculator::put(shared_ptr<const AudioBuffers> audio, dcpomatic::DCPTime ti
 		if (_current_frames == frames_per_measurement) {
 			{
 				boost::mutex::scoped_lock lm(_store_mutex);
-				_peaks.emplace_back(time + dcpomatic::DCPTime::from_frames(frame, frame_rate), _current_peaks);
+				_peaks.emplace_back(time + dcpomatic::DCPTime::from_frames(frame + 1, frame_rate), _current_peaks);
+			}
+			for (auto channel = 0; channel < channels; ++channel) {
+				_current_peaks[channel] *= _falloff_linear;
 			}
-			std::fill(_current_peaks.begin(), _current_peaks.end(), 0.0f);
 			_current_frames = 0;
 		}
 	}
diff --git a/src/lib/level_calculator.h b/src/lib/level_calculator.h
index 9eeb5b9b8..e4d571cd4 100644
--- a/src/lib/level_calculator.h
+++ b/src/lib/level_calculator.h
@@ -34,7 +34,10 @@ class AudioBuffers;
 class LevelCalculator
 {
 public:
-	LevelCalculator();
+	/** @param calculation_frame_rate number of peak calculations to make per second
+	 *  @param falloff meter falloff in db/sec
+	 */
+	LevelCalculator(int calculation_frame_rate = 30, int falloff = 15);
 
 	LevelCalculator(LevelCalculator const&) = delete;
 	LevelCalculator& operator=(LevelCalculator const&) = delete;
@@ -46,6 +49,9 @@ public:
 	void enable(bool e);
 
 private:
+	int const _calculation_frame_rate;
+	float const _falloff_linear;
+
 	boost::mutex _current_mutex;
 	std::vector<float> _current_peaks;
 	int _current_frames = 0;
diff --git a/test/level_calculator_test.cc b/test/level_calculator_test.cc
new file mode 100644
index 000000000..828f834b4
--- /dev/null
+++ b/test/level_calculator_test.cc
@@ -0,0 +1,43 @@
+/*
+    Copyright (C) 2025 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+#include "lib/audio_buffers.h"
+#include "lib/level_calculator.h"
+#include <boost/test/unit_test.hpp>
+
+
+using std::make_shared;
+
+
+BOOST_AUTO_TEST_CASE(level_calculator_falloff_correct)
+{
+	auto pulse = make_shared<AudioBuffers>(6, 96000);
+	pulse->make_silent();
+
+	pulse->data()[0][0] = 1;
+
+	LevelCalculator calc(30, 15);
+	calc.enable(true);
+	calc.put(pulse, {}, 48000);
+
+	BOOST_CHECK_CLOSE(calc.get(dcpomatic::DCPTime::from_frames(31, 30))[0], pow(10, -15.0 / 20), 0.0001);
+}
+
diff --git a/test/wscript b/test/wscript
index b568872a3..b9eaad41f 100644
--- a/test/wscript
+++ b/test/wscript
@@ -128,6 +128,7 @@ def build(bld):
                  kdm_cli_test.cc
                  kdm_naming_test.cc
                  kdm_util_test.cc
+                 level_calculator_test.cc
                  low_bitrate_test.cc
                  markers_test.cc
                  map_cli_test.cc