Add fade in/out option to the content audio tab (#1026).

6 files changed, 139 insertions, 6 deletions

diff --git a/src/lib/audio_content.cc b/src/lib/audio_content.cc
index 32e713ff2..ad8d7df0f 100644
--- a/src/lib/audio_content.cc
+++ b/src/lib/audio_content.cc
@@ -53,6 +53,8 @@ using namespace dcpomatic;
 int const AudioContentProperty::STREAMS = 200;
 int const AudioContentProperty::GAIN = 201;
 int const AudioContentProperty::DELAY = 202;
+int const AudioContentProperty::FADE_IN = 203;
+int const AudioContentProperty::FADE_OUT = 204;
 
 
 AudioContent::AudioContent (Content* parent)
@@ -90,6 +92,8 @@ AudioContent::AudioContent (Content* parent, cxml::ConstNodePtr node)
 {
 	_gain = node->number_child<double> ("AudioGain");
 	_delay = node->number_child<int> ("AudioDelay");
+	_fade_in = ContentTime(node->optional_number_child<ContentTime::Type>("AudioFadeIn").get_value_or(0));
+	_fade_out = ContentTime(node->optional_number_child<ContentTime::Type>("AudioFadeOut").get_value_or(0));
 
 	/* Backwards compatibility */
 	auto r = node->optional_number_child<double>("AudioVideoFrameRate");
@@ -127,6 +131,8 @@ AudioContent::as_xml (xmlpp::Node* node) const
 	boost::mutex::scoped_lock lm (_mutex);
 	node->add_child("AudioGain")->add_child_text(raw_convert<string>(_gain));
 	node->add_child("AudioDelay")->add_child_text(raw_convert<string>(_delay));
+	node->add_child("AudioFadeIn")->add_child_text(raw_convert<string>(_fade_in.get()));
+	node->add_child("AudioFadeOut")->add_child_text(raw_convert<string>(_fade_out.get()));
 }
 
 
@@ -420,3 +426,57 @@ AudioContent::modify_trim_start (ContentTime& trim) const
 	/* XXX: we're in trouble if streams have different rates */
 	trim = trim.round (_streams.front()->frame_rate());
 }
+
+
+void
+AudioContent::set_fade_in (ContentTime t)
+{
+	maybe_set (_fade_in, t, AudioContentProperty::FADE_IN);
+}
+
+
+void
+AudioContent::set_fade_out (ContentTime t)
+{
+	maybe_set (_fade_out, t, AudioContentProperty::FADE_OUT);
+}
+
+
+vector<float>
+AudioContent::fade (AudioStreamPtr stream, Frame frame, Frame length, int frame_rate) const
+{
+	auto const in = fade_in().frames_round(frame_rate);
+	auto const out = fade_out().frames_round(frame_rate);
+
+	/* Where the start trim ends, at frame_rate */
+	auto const trim_start = _parent->trim_start().frames_round(frame_rate);
+	/* Where the end trim starts within the whole length of the content, at frame_rate */
+	auto const trim_end = ContentTime(ContentTime::from_frames(stream->length(), stream->frame_rate()) - _parent->trim_end()).frames_round(frame_rate);
+
+	if (
+		(in == 0  || (frame >= (trim_start + in))) &&
+		(out == 0 || ((frame + length) < (trim_end - out)))
+	   ) {
+		/* This section starts after the fade in and ends before the fade out */
+		return {};
+	}
+
+	/* Start position relative to the start of the fade in */
+	auto in_start = frame - trim_start;
+	/* Start position relative to the start of the fade out */
+	auto out_start = frame - (trim_end - out);
+
+	vector<float> coeffs(length);
+	for (auto coeff = 0; coeff < length; ++coeff) {
+		coeffs[coeff] = 1.0;
+		if (in) {
+			coeffs[coeff] *= logarithmic_fade_in_curve(static_cast<float>(in_start + coeff) / in);
+		}
+		if (out) {
+			coeffs[coeff] *= logarithmic_fade_out_curve(static_cast<float>(out_start + coeff) / out);
+		}
+	}
+
+	return coeffs;
+}
+
diff --git a/src/lib/audio_content.h b/src/lib/audio_content.h
index 4dc45f114..ba998a5ad 100644
--- a/src/lib/audio_content.h
+++ b/src/lib/audio_content.h
@@ -42,6 +42,8 @@ public:
 	static int const STREAMS;
 	static int const GAIN;
 	static int const DELAY;
+	static int const FADE_IN;
+	static int const FADE_OUT;
 };
 
 
@@ -76,6 +78,19 @@ public:
 		return _delay;
 	}
 
+	dcpomatic::ContentTime fade_in () const {
+		boost::mutex::scoped_lock lm (_mutex);
+		return _fade_in;
+	}
+
+	dcpomatic::ContentTime fade_out () const {
+		boost::mutex::scoped_lock lm (_mutex);
+		return _fade_out;
+	}
+
+	void set_fade_in (dcpomatic::ContentTime time);
+	void set_fade_out (dcpomatic::ContentTime time);
+
 	std::string processing_description (std::shared_ptr<const Film> film) const;
 
 	std::vector<AudioStreamPtr> streams () const {
@@ -93,6 +108,13 @@ public:
 	void modify_position (std::shared_ptr<const Film> film, dcpomatic::DCPTime& pos) const;
 	void modify_trim_start (dcpomatic::ContentTime& pos) const;
 
+	/** @param frame frame within the whole (untrimmed) content.
+	 *  @param frame_rate The frame rate of the audio (it may have been resampled).
+	 *  @return a fade coefficient for @ref length samples starting at an offset @frame within
+	 *  the content, or an empty vector if the given section has no fade.
+	 */
+	std::vector<float> fade (AudioStreamPtr stream, Frame frame, Frame length, int frame_rate) const;
+
 	static std::shared_ptr<AudioContent> from_xml (Content* parent, cxml::ConstNodePtr, int version);
 
 private:
@@ -101,6 +123,8 @@ private:
 	double _gain = 0;
 	/** Delay to apply to audio (positive moves audio later) in milliseconds */
 	int _delay = 0;
+	dcpomatic::ContentTime _fade_in;
+	dcpomatic::ContentTime _fade_out;
 	std::vector<AudioStreamPtr> _streams;
 };
 
diff --git a/src/lib/maths_util.cc b/src/lib/maths_util.cc
index 35e3879c4..76681afb6 100644
--- a/src/lib/maths_util.cc
+++ b/src/lib/maths_util.cc
@@ -19,6 +19,7 @@
 */
 
 
+#include "maths_util.h"
 #include <cmath>
 
 
@@ -35,3 +36,19 @@ linear_to_db (double linear)
 	return 20 * log10(linear);
 }
 
+
+float
+logarithmic_fade_in_curve (float t)
+{
+	auto const c = clamp(t, 0.0f, 1.0f);
+	return std::exp(2 * (c - 1)) * c;
+}
+
+
+float
+logarithmic_fade_out_curve (float t)
+{
+	auto const c = clamp(t, 0.0f, 1.0f);
+	return std::exp(-2 * c) * (1 - c);
+}
+
diff --git a/src/lib/maths_util.h b/src/lib/maths_util.h
index 8adefbbc4..24c4b547f 100644
--- a/src/lib/maths_util.h
+++ b/src/lib/maths_util.h
@@ -30,6 +30,21 @@
 extern double db_to_linear (double db);
 extern double linear_to_db (double linear);
 
+/** @return linear gain according to a logarithmic curve, for fading in.
+ *  t < 0:       linear gain of 0
+ *  0 >= t >= 1: logarithmic fade in curve
+ *  t > 1:       linear gain of 1
+ */
+extern float logarithmic_fade_in_curve (float t);
+
+
+/** @return linear gain according to a logarithmic curve, for fading out.
+ *  t > 1:       linear gain of 0
+ *  0 >= t >= 1: logarithmic fade out curve
+ *  t < 0:       linear gain of 1
+ */
+extern float logarithmic_fade_out_curve (float t);
+
 
 template <class T>
 T clamp (T val, T minimum, T maximum)
diff --git a/src/lib/player.cc b/src/lib/player.cc
index abd051bed..12a53bc63 100644
--- a/src/lib/player.cc
+++ b/src/lib/player.cc
@@ -1049,12 +1049,28 @@ Player::audio (weak_ptr<Piece> wp, AudioStreamPtr stream, ContentAudio content_a
 
 	DCPOMATIC_ASSERT (content_audio.audio->frames() > 0);
 
-	/* Gain */
-
-	if (content->gain() != 0) {
-		auto gain = make_shared<AudioBuffers>(content_audio.audio);
-		gain->apply_gain (content->gain());
-		content_audio.audio = gain;
+	/* Gain and fade */
+
+	auto const fade_coeffs = content->fade (stream, content_audio.frame, content_audio.audio->frames(), rfr);
+	if (content->gain() != 0 || !fade_coeffs.empty()) {
+		auto gain_buffers = make_shared<AudioBuffers>(content_audio.audio);
+		if (!fade_coeffs.empty()) {
+			/* Apply both fade and gain */
+			DCPOMATIC_ASSERT (fade_coeffs.size() == static_cast<size_t>(gain_buffers->frames()));
+			auto const channels = gain_buffers->channels();
+			auto const frames = fade_coeffs.size();
+			auto data = gain_buffers->data();
+			auto const gain = db_to_linear (content->gain());
+			for (auto channel = 0; channel < channels; ++channel) {
+				for (auto frame = 0U; frame < frames; ++frame) {
+					data[channel][frame] *= gain * fade_coeffs[frame];
+				}
+			}
+		} else {
+			/* Just apply gain */
+			gain_buffers->apply_gain (content->gain());
+		}
+		content_audio.audio = gain_buffers;
 	}
 
 	/* Remap */
diff --git a/src/lib/video_content.cc b/src/lib/video_content.cc
index 9ff35ffdf..853204575 100644
--- a/src/lib/video_content.cc
+++ b/src/lib/video_content.cc
@@ -173,6 +173,7 @@ VideoContent::VideoContent (Content* parent, cxml::ConstNodePtr node, int versio
 	_yuv = node->optional_bool_child("YUV").get_value_or (true);
 
 	if (version >= 32) {
+		/* These should be VideoFadeIn and VideoFadeOut but we'll leave them like this until 2.18.x */
 		_fade_in = node->number_child<Frame> ("FadeIn");
 		_fade_out = node->number_child<Frame> ("FadeOut");
 	} else {