UI: Add option to disable audio ducking on windows

The audio subsystem of windows is by default configured to lower the
volume of other things while a communications device (mic) is currently
active.  This patch prevents that from being enabled with OBS.  If the
user needs audio ducking enabled again for whatever reason, there is now
an option to re-enable it in advanced settings.

Closes jp9000/obs-studio#884

UI/data/locale/en-US.ini

@@ -610,6 +610,7 @@ Basic.Settings.Advanced.Video.ColorRange.Partial="Partial"
 Basic.Settings.Advanced.Video.ColorRange.Full="Full"
 Basic.Settings.Advanced.Audio.MonitoringDevice="Audio Monitoring Device"
 Basic.Settings.Advanced.Audio.MonitoringDevice.Default="Default"
+Basic.Settings.Advanced.Audio.DisableAudioDucking="Disable Windows audio ducking"
 Basic.Settings.Advanced.StreamDelay="Stream Delay"
 Basic.Settings.Advanced.StreamDelay.Duration="Duration (seconds)"
 Basic.Settings.Advanced.StreamDelay.Preserve="Preserve cutoff point (increase delay) when reconnecting"

UI/forms/OBSBasicSettings.ui

@@ -3755,6 +3755,13 @@
                    <item row="0" column="1">
                     <widget class="QComboBox" name="monitoringDevice"/>
                    </item>
+                   <item row="1" column="1">
+                    <widget class="QCheckBox" name="disableAudioDucking">
+                     <property name="text">
+                      <string>Basic.Settings.Advanced.Audio.DisableAudioDucking</string>
+                     </property>
+                    </widget>
+                   </item>
                   </layout>
                  </widget>
                 </item>

UI/obs-app.cpp

@@ -410,6 +410,11 @@ bool OBSApp::InitGlobalConfigDefaults()
 	config_set_default_bool(globalConfig, "BasicWindow",
 			"ShowStatusBar", true);
 
+#ifdef _WIN32
+	config_set_default_bool(globalConfig, "Audio", "DisableAudioDucking",
+			true);
+#endif
+
 #ifdef __APPLE__
 	config_set_default_bool(globalConfig, "Video", "DisableOSXVSync", true);
 	config_set_default_bool(globalConfig, "Video", "ResetOSXVSyncOnExit",
@@ -733,6 +738,13 @@ OBSApp::OBSApp(int &argc, char **argv, profiler_name_store_t *store)
 
 OBSApp::~OBSApp()
 {
+#ifdef _WIN32
+	bool disableAudioDucking = config_get_bool(globalConfig, "Audio",
+			"DisableAudioDucking");
+	if (disableAudioDucking)
+		DisableAudioDucking(false);
+#endif
+
 #ifdef __APPLE__
 	bool vsyncDiabled = config_get_bool(globalConfig, "Video",
 			"DisableOSXVSync");
@@ -851,6 +863,13 @@ void OBSApp::AppInit()
 	config_set_default_string(globalConfig, "Basic", "SceneCollectionFile",
 			Str("Untitled"));
 
+#ifdef _WIN32
+	bool disableAudioDucking = config_get_bool(globalConfig, "Audio",
+			"DisableAudioDucking");
+	if (disableAudioDucking)
+		DisableAudioDucking(true);
+#endif
+
 #ifdef __APPLE__
 	if (config_get_bool(globalConfig, "Video", "DisableOSXVSync"))
 		EnableOSXVSync(false);

UI/platform-windows.cpp

@@ -30,6 +30,11 @@ using namespace std;
 #include <shellapi.h>
 #include <shlobj.h>
 #include <Dwmapi.h>
+#include <mmdeviceapi.h>
+#include <audiopolicy.h>
+
+#include <util/windows/HRError.hpp>
+#include <util/windows/ComPtr.hpp>
 
 static inline bool check_path(const char* data, const char *path,
 		string &output)
@@ -216,3 +221,41 @@ void SetWin32DropStyle(QWidget *window)
 	ex_style |= WS_EX_ACCEPTFILES;
 	SetWindowLongPtr(hwnd, GWL_EXSTYLE, ex_style);
 }
+
+bool DisableAudioDucking(bool disable)
+{
+	ComPtr<IMMDeviceEnumerator>   devEmum;
+	ComPtr<IMMDevice>             device;
+	ComPtr<IAudioSessionManager2> sessionManager2;
+	ComPtr<IAudioSessionControl>  sessionControl;
+	ComPtr<IAudioSessionControl2> sessionControl2;
+
+	HRESULT result = CoCreateInstance(__uuidof(MMDeviceEnumerator),
+			nullptr, CLSCTX_INPROC_SERVER,
+			__uuidof(IMMDeviceEnumerator),
+			(void **)&devEmum);
+	if (FAILED(result))
+		return false;
+
+	result = devEmum->GetDefaultAudioEndpoint(eRender, eConsole, &device);
+	if (FAILED(result))
+		return false;
+
+	result = device->Activate(__uuidof(IAudioSessionManager2),
+			CLSCTX_INPROC_SERVER, nullptr,
+			(void **)&sessionManager2);
+	if (FAILED(result))
+		return false;
+
+	result = sessionManager2->GetAudioSessionControl(nullptr, 0,
+			&sessionControl);
+	if (FAILED(result))
+		return false;
+
+	result = sessionControl->QueryInterface(&sessionControl2);
+	if (FAILED(result))
+		return false;
+
+	result = sessionControl2->SetDuckingPreference(disable);
+	return SUCCEEDED(result);
+}

UI/platform.hpp

@@ -42,6 +42,7 @@ uint32_t GetWindowsVersion();
 void SetAeroEnabled(bool enable);
 void SetProcessPriority(const char *priority);
 void SetWin32DropStyle(QWidget *window);
+bool DisableAudioDucking(bool disable);
 #endif
 
 #ifdef __APPLE__

UI/window-basic-settings.cpp

@@ -392,6 +392,9 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 	HookWidget(ui->resetOSXVSync,        CHECK_CHANGED,  ADV_CHANGED);
 #if defined(_WIN32) || defined(__APPLE__)
 	HookWidget(ui->monitoringDevice,     COMBO_CHANGED,  ADV_CHANGED);
+#endif
+#ifdef _WIN32
+	HookWidget(ui->disableAudioDucking,  CHECK_CHANGED,  ADV_CHANGED);
 #endif
 	HookWidget(ui->filenameFormatting,   EDIT_CHANGED,   ADV_CHANGED);
 	HookWidget(ui->overwriteIfExists,    CHECK_CHANGED,  ADV_CHANGED);
@@ -461,6 +464,7 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 	delete ui->advancedGeneralGroupBox;
 	delete ui->enableNewSocketLoop;
 	delete ui->enableLowLatencyMode;
+	delete ui->disableAudioDucking;
 	ui->rendererLabel = nullptr;
 	ui->renderer = nullptr;
 	ui->adapterLabel = nullptr;
@@ -470,6 +474,7 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 	ui->advancedGeneralGroupBox = nullptr;
 	ui->enableNewSocketLoop = nullptr;
 	ui->enableLowLatencyMode = nullptr;
+	ui->disableAudioDucking = nullptr;
 #endif
 
 #ifndef __APPLE__
@@ -2065,6 +2070,10 @@ void OBSBasicSettings::LoadAdvancedSettings()
 	ui->resetOSXVSync->setChecked(resetOSXVSync);
 	ui->resetOSXVSync->setEnabled(disableOSXVSync);
 #elif _WIN32
+	bool disableAudioDucking = config_get_bool(App()->GlobalConfig(),
+			"Audio", "DisableAudioDucking");
+	ui->disableAudioDucking->setChecked(disableAudioDucking);
+
 	const char *processPriority = config_get_string(App()->GlobalConfig(),
 			"General", "ProcessPriority");
 	bool enableNewSocketLoop = config_get_bool(main->Config(), "Output",
@@ -2585,6 +2594,16 @@ void OBSBasicSettings::SaveAdvancedSettings()
 	SaveCombo(ui->monitoringDevice, "Audio", "MonitoringDeviceName");
 	SaveComboData(ui->monitoringDevice, "Audio", "MonitoringDeviceId");
 #endif
+
+#ifdef _WIN32
+	if (WidgetChanged(ui->disableAudioDucking)) {
+		bool disable = ui->disableAudioDucking->isChecked();
+		config_set_bool(App()->GlobalConfig(),
+				"Audio", "DisableAudioDucking", disable);
+		DisableAudioDucking(disable);
+	}
+#endif
+
 	SaveEdit(ui->filenameFormatting, "Output", "FilenameFormatting");
 	SaveEdit(ui->simpleRBPrefix, "SimpleOutput", "RecRBPrefix");
 	SaveEdit(ui->simpleRBSuffix, "SimpleOutput", "RecRBSuffix");