pcm/MixRampAnalyzer: a MixRamp implementation

src/pcm/MixRampAnalyzer.cxx

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "MixRampAnalyzer.hxx"
+#include "util/ConstBuffer.hxx"
+
+inline void
+MixRampData::Add(MixRampItem item) noexcept
+{
+	for (std::size_t i = 0; i < mixramp_volumes.size(); ++i) {
+		if (start[i].time < FloatDuration{} &&
+		    item.volume >= mixramp_volumes[i])
+			start[i] = item;
+
+		if (item.volume >= mixramp_volumes[i])
+			end[i] = item;
+	}
+
+}
+
+void
+MixRampAnalyzer::Process(ConstBuffer<ReplayGainAnalyzer::Frame> src) noexcept
+{
+	while (!src.empty()) {
+		std::size_t chunk_remaining = chunk_frames - chunk_fill;
+		assert(chunk_remaining > 0);
+
+		if (chunk_remaining > src.size) {
+			gain_analyzer.Process(src);
+			chunk_fill += src.size;
+			return;
+		}
+
+		gain_analyzer.Process({src.data, chunk_remaining});
+		src.skip_front(chunk_remaining);
+
+		gain_analyzer.Flush();
+
+		const double gain = (double)gain_analyzer.GetGain();
+		const double volume = -gain;
+
+		result.Add({GetTime(), volume});
+
+		++chunk_number;
+		chunk_fill = 0;
+		gain_analyzer = {};
+	}
+}

src/pcm/MixRampAnalyzer.hxx

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#pragma once
+
+#include "ReplayGainAnalyzer.hxx"
+#include "Chrono.hxx"
+
+constexpr auto mixramp_volumes = std::array{
+	-90., -60., -40., -30., -24., -21., -18.,
+	-15., -12., -9., -6., -3.,  0.,  3.,  6.,
+};
+
+struct MixRampItem {
+	FloatDuration time;
+	double volume;
+
+	constexpr bool operator==(const MixRampItem &other) const noexcept {
+		return time == other.time && volume == other.volume;
+	}
+
+	constexpr bool operator!=(const MixRampItem &other) const noexcept {
+		return !(*this == other);
+	}
+};
+
+using MixRampArray = std::array<MixRampItem, mixramp_volumes.size()>;
+
+struct MixRampData {
+	MixRampArray start, end;
+
+	constexpr MixRampData() noexcept:start{}, end{} {
+		for (std::size_t i = 0; i < mixramp_volumes.size(); ++i) {
+			start[i].time = end[i].time = FloatDuration{-1};
+			start[i].volume = end[i].volume = mixramp_volumes[i];
+		}
+	}
+
+	void Add(MixRampItem item) noexcept;
+};
+
+/**
+ * Analyze a 44.1 kHz / stereo / float32 audio stream and calculate
+ * MixRamp tags.
+ */
+class MixRampAnalyzer {
+	static constexpr std::size_t chunk_duration_fraction = 10;
+	static constexpr std::size_t chunk_frames =
+		ReplayGainAnalyzer::SAMPLE_RATE / chunk_duration_fraction;
+	static constexpr FloatDuration chunk_duration{1.0 / chunk_duration_fraction};
+
+	WindowReplayGainAnalyzer gain_analyzer;
+
+	MixRampData result;
+
+	std::size_t chunk_number = 0;
+
+	std::size_t chunk_fill = 0;
+
+public:
+	void Process(ConstBuffer<ReplayGainAnalyzer::Frame> src) noexcept;
+
+	FloatDuration GetTime() const noexcept {
+		return chunk_number * chunk_duration;
+	}
+
+	const auto &GetResult() const noexcept {
+		return result;
+	}
+};

src/pcm/meson.build

@@ -48,6 +48,7 @@ pcm_sources = [
   'ConfiguredResampler.cxx',
   'AudioCompress/compress.c',
   'ReplayGainAnalyzer.cxx',
+  'MixRampAnalyzer.cxx',
 ]
 
 libsamplerate_dep = dependency('samplerate', version: '>= 0.1.3', required: get_option('libsamplerate'))

test/RunMixRampAnalyzer.cxx

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "ReadFrames.hxx"
+#include "pcm/MixRampAnalyzer.hxx"
+#include "io/FileDescriptor.hxx"
+#include "util/ConstBuffer.hxx"
+#include "util/PrintException.hxx"
+
+#include <array>
+#include <memory>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int
+main(int, char **) noexcept
+try {
+	constexpr std::size_t frame_size = sizeof(ReplayGainAnalyzer::Frame);
+
+	const FileDescriptor input_fd(STDIN_FILENO);
+
+	MixRampAnalyzer a;
+
+	while (true) {
+		std::array<ReplayGainAnalyzer::Frame, 4096> buffer;
+
+		size_t nbytes = ReadFrames(input_fd,
+					   buffer.data(), sizeof(buffer),
+					   frame_size);
+		if (nbytes == 0)
+			break;
+
+		const std::size_t n_frames = nbytes / frame_size;
+		a.Process({buffer.data(), n_frames});
+	}
+
+	const auto data = a.GetResult();
+
+	const auto total_time = a.GetTime();
+
+	printf("MIXRAMP_START=");
+
+	MixRampItem last{};
+
+	for (const auto &i : data.start) {
+		if (i.time >= FloatDuration{} && i != last) {
+			printf("%.2f %.2f;", i.volume, i.time.count());
+			last = i;
+		}
+	}
+
+	printf("\n");
+
+	printf("MIXRAMP_END=");
+	last = {};
+	for (const auto &i : data.end) {
+		if (i.time >= FloatDuration{} && i != last) {
+			printf("%.2f %.2f;", i.volume, (total_time - i.time).count());
+			last = i;
+		}
+	}
+	printf("\n");
+
+	return EXIT_SUCCESS;
+} catch (...) {
+	PrintException(std::current_exception());
+	return EXIT_FAILURE;
+}

test/meson.build

@@ -567,6 +567,17 @@ executable(
   ],
 )
 
+executable(
+  'RunMixRampAnalyzer',
+  'RunMixRampAnalyzer.cxx',
+  'ReadFrames.cxx',
+  include_directories: inc,
+  dependencies: [
+    pcm_dep,
+    io_dep,
+  ],
+)
+
 #
 # Encoder
 #