Add volume curve setting

include/config.hpp

@@ -1,12 +1,21 @@
 #pragma once
 #include <filesystem>
+#include <string>
 
 #include "audio/dsp_core.hpp"
-#include "renderer.hpp"
 #include "frontend_settings.hpp"
+#include "renderer.hpp"
 
 struct AudioDeviceConfig {
+	// Audio curve to use for volumes between 0-100
+	enum class VolumeCurve : int {
+		Cubic = 0,   // Samples are scaled by volume ^ 3
+		Linear = 1,  // Samples are scaled by volume
+	};
+
 	float volumeRaw = 1.0f;
+	VolumeCurve volumeCurve = VolumeCurve::Cubic;
+
 	bool muteAudio = false;
 
 	float getVolume() const {
@@ -16,6 +25,9 @@ struct AudioDeviceConfig {
 
 		return volumeRaw;
 	}
+
+	static VolumeCurve volumeCurveFromString(std::string inString);
+	static const char* volumeCurveToString(VolumeCurve curve);
 };
 
 // Remember to initialize every field here to its default value otherwise bad things will happen

src/config.cpp

@@ -1,5 +1,7 @@
 #include "config.hpp"
 
+#include <algorithm>
+#include <cctype>
 #include <cmath>
 #include <fstream>
 #include <map>
@@ -105,6 +107,7 @@ void EmulatorConfig::load() {
 			// Our volume ranges from 0.0 (muted) to 2.0 (boosted, using a logarithmic scale). 1.0 is the "default" volume, ie we don't adjust the PCM
 			// samples at all.
 			audioDeviceConfig.volumeRaw = float(std::clamp(toml::find_or<toml::floating>(audio, "AudioVolume", 1.0), 0.0, 2.0));
+			audioDeviceConfig.volumeCurve = AudioDeviceConfig::volumeCurveFromString(toml::find_or<std::string>(audio, "VolumeCurve", "cubic"));
 		}
 	}
 
@@ -188,6 +191,7 @@ void EmulatorConfig::save() {
 	data["Audio"]["EnableAACAudio"] = aacEnabled;
 	data["Audio"]["MuteAudio"] = audioDeviceConfig.muteAudio;
 	data["Audio"]["AudioVolume"] = double(audioDeviceConfig.volumeRaw);
+	data["Audio"]["VolumeCurve"] = std::string(AudioDeviceConfig::volumeCurveToString(audioDeviceConfig.volumeCurve));
 	data["Audio"]["PrintDSPFirmware"] = printDSPFirmware;
 
 	data["Battery"]["ChargerPlugged"] = chargerPlugged;
@@ -203,3 +207,26 @@ void EmulatorConfig::save() {
 	file << data;
 	file.close();
 }
+
+AudioDeviceConfig::VolumeCurve AudioDeviceConfig::volumeCurveFromString(std::string inString) {
+	// Transform to lower-case to make the setting case-insensitive
+	std::transform(inString.begin(), inString.end(), inString.begin(), [](unsigned char c) { return std::tolower(c); });
+
+	if (inString == "cubic") {
+		return VolumeCurve::Cubic;
+	} else if (inString == "linear") {
+		return VolumeCurve::Linear;
+	}
+
+	// Default to cubic curve
+	return VolumeCurve::Cubic;
+}
+
+const char* AudioDeviceConfig::volumeCurveToString(AudioDeviceConfig::VolumeCurve curve) {
+	switch (curve) {
+		case VolumeCurve::Linear: return "linear";
+
+		case VolumeCurve::Cubic:
+		default: return "cubic";
+	}
+}

src/core/audio/miniaudio_device.cpp

@@ -134,6 +134,12 @@ void MiniAudioDevice::init(Samples& samples, bool safe) {
 			} else {
 				// If our volume is in [0.0, 1.0) then just multiply by the volume. No need to clamp, since there is no danger of our samples wrapping
 				// around due to overflow
+
+				// If we're applying cubic volume curve, raise volume to the power of 3
+				if (self->audioSettings.volumeCurve == AudioDeviceConfig::VolumeCurve::Cubic) {
+					audioVolume = audioVolume * audioVolume * audioVolume;
+				}
+
 				for (usize i = 0; i < samplesWritten; i += 2) {
 					s16 l = s16(float(sample[0]) * audioVolume);
 					s16 r = s16(float(sample[1]) * audioVolume);

src/panda_qt/config_window.cpp

@@ -240,6 +240,16 @@ ConfigWindow::ConfigWindow(ConfigCallback configCallback, MainWindowCallback win
 	connectCheckbox(muteAudio, config.audioDeviceConfig.muteAudio);
 	audioLayout->addRow(muteAudio);
 
+	QComboBox* volumeCurveType = new QComboBox;
+	volumeCurveType->addItem(tr("Cubic"));
+	volumeCurveType->addItem(tr("Linear"));
+	volumeCurveType->setCurrentIndex(static_cast<int>(config.audioDeviceConfig.volumeCurve));
+	connect(volumeCurveType, &QComboBox::currentIndexChanged, this, [&](int index) {
+		config.audioDeviceConfig.volumeCurve = static_cast<AudioDeviceConfig::VolumeCurve>(index);
+		updateConfig();
+	});
+	audioLayout->addRow(tr("Volume curve"), volumeCurveType);
+
 	QSpinBox* volumeRaw = new QSpinBox();
 	volumeRaw->setRange(0, 200);
 	volumeRaw->setValue(config.audioDeviceConfig.volumeRaw * 100);