UI: Add low latency audio buffering mode to UI

This feature is meant to reduce maximum audio buffering and turn off
dynamic buffering mode. This allows the lowest possible consistent
latency for audio buffering, which is useful for the decklink and NDI
outputs which cannot rely on audio timestamps for synchronization.

This can have a negative effect of making audio segments (partial or in
full) cut out. So audio glitching or audio loss can occur if this is
enabled.

UI/data/locale/en-US.ini

@@ -1044,6 +1044,11 @@ Basic.Settings.Audio.EnablePushToTalk="Enable Push-to-talk"
 Basic.Settings.Audio.PushToTalkDelay="Push-to-talk delay"
 Basic.Settings.Audio.UnknownAudioDevice="[Device not connected or not available]"
 Basic.Settings.Audio.Disabled="Disabled"
+Basic.Settings.Audio.LowLatencyBufferingMode="Low Latency Audio Buffering Mode (For Decklink/NDI outputs)"
+Basic.Settings.Audio.LowLatencyBufferingWarning.Enabled="WARNING: Low latency audio buffering is enabled."
+Basic.Settings.Audio.LowLatencyBufferingWarning="Low latency audio buffering mode may cause audio to glitch or stop playing from some sources."
+Basic.Settings.Audio.LowLatencyBufferingWarning.Title="Enable low latency audio buffering mode?"
+Basic.Settings.Audio.LowLatencyBufferingWarning.Confirm="Are you sure you want to enable low latency audio buffering mode?"
 
 # basic mode 'advanced' settings
 Basic.Settings.Advanced="Advanced"

UI/forms/OBSBasicSettings.ui

@@ -151,8 +151,8 @@
              <rect>
               <x>0</x>
               <y>0</y>
-              <width>806</width>
-              <height>1181</height>
+              <width>803</width>
+              <height>1226</height>
              </rect>
             </property>
             <layout class="QVBoxLayout" name="verticalLayout_19">
@@ -1379,7 +1379,7 @@
               <x>0</x>
               <y>0</y>
               <width>820</width>
-              <height>679</height>
+              <height>676</height>
              </rect>
             </property>
             <layout class="QVBoxLayout" name="verticalLayout_21">
@@ -3972,7 +3972,7 @@
               <x>0</x>
               <y>0</y>
               <width>820</width>
-              <height>641</height>
+              <height>632</height>
              </rect>
             </property>
             <layout class="QVBoxLayout" name="verticalLayout_50">
@@ -4372,6 +4372,13 @@
                      </property>
                     </widget>
                    </item>
+                   <item row="2" column="1">
+                    <widget class="QCheckBox" name="lowLatencyBuffering">
+                     <property name="text">
+                      <string>Basic.Settings.Audio.LowLatencyBufferingMode</string>
+                     </property>
+                    </widget>
+                   </item>
                   </layout>
                  </widget>
                 </item>
@@ -4904,8 +4911,8 @@
              <rect>
               <x>0</x>
               <y>0</y>
-              <width>609</width>
-              <height>870</height>
+              <width>713</width>
+              <height>923</height>
              </rect>
             </property>
             <layout class="QVBoxLayout" name="verticalLayout_23">
@@ -5925,7 +5932,7 @@
   <tabstop>peakMeterType</tabstop>
   <tabstop>monitoringDevice</tabstop>
   <tabstop>disableAudioDucking</tabstop>
-  <tabstop>baseResolution</tabstop>
+  <tabstop>lowLatencyBuffering</tabstop>
   <tabstop>outputResolution</tabstop>
   <tabstop>downscaleFilter</tabstop>
   <tabstop>fpsType</tabstop>
@@ -5960,6 +5967,18 @@
   <tabstop>enableLowLatencyMode</tabstop>
   <tabstop>browserHWAccel</tabstop>
   <tabstop>hotkeyFocusType</tabstop>
+  <tabstop>hideOBSFromCapture</tabstop>
+  <tabstop>closeProjectors</tabstop>
+  <tabstop>moreInfoButton</tabstop>
+  <tabstop>ignoreRecommended</tabstop>
+  <tabstop>useStreamKeyAdv</tabstop>
+  <tabstop>baseResolution</tabstop>
+  <tabstop>hotkeyFilterSearch</tabstop>
+  <tabstop>hotkeyFilterInput</tabstop>
+  <tabstop>hotkeyFilterReset</tabstop>
+  <tabstop>hotkeyScrollArea</tabstop>
+  <tabstop>sdrWhiteLevel</tabstop>
+  <tabstop>hdrNominalPeakLevel</tabstop>
  </tabstops>
  <resources>
   <include location="obs.qrc"/>

UI/window-basic-main.cpp

@@ -4409,7 +4409,7 @@ bool OBSBasic::ResetAudio()
 {
 	ProfileScope("OBSBasic::ResetAudio");
 
-	struct obs_audio_info ai;
+	struct obs_audio_info2 ai = {};
 	ai.samples_per_sec =
 		config_get_uint(basicConfig, "Audio", "SampleRate");
 
@@ -4431,7 +4431,14 @@ bool OBSBasic::ResetAudio()
 	else
 		ai.speakers = SPEAKERS_STEREO;
 
-	return obs_reset_audio(&ai);
+	bool lowLatencyAudioBuffering = config_get_bool(
+		GetGlobalConfig(), "Audio", "LowLatencyAudioBuffering");
+	if (lowLatencyAudioBuffering) {
+		ai.max_buffering_ms = 20;
+		ai.fixed_buffering = true;
+	}
+
+	return obs_reset_audio2(&ai);
 }
 
 extern char *get_new_source_name(const char *name, const char *format);

UI/window-basic-settings.cpp

@@ -760,6 +760,8 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 		SLOT(SurroundWarning(int)));
 	connect(ui->channelSetup, SIGNAL(currentIndexChanged(int)), this,
 		SLOT(SpeakerLayoutChanged(int)));
+	connect(ui->lowLatencyBuffering, SIGNAL(clicked(bool)), this,
+		SLOT(LowLatencyBufferingChanged(bool)));
 	connect(ui->simpleOutRecQuality, SIGNAL(currentIndexChanged(int)), this,
 		SLOT(SimpleRecordingQualityChanged()));
 	connect(ui->simpleOutRecQuality, SIGNAL(currentIndexChanged(int)), this,
@@ -926,6 +928,7 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 
 	channelIndex = ui->channelSetup->currentIndex();
 	sampleRateIndex = ui->sampleRate->currentIndex();
+	llBufferingEnabled = ui->lowLatencyBuffering->isChecked();
 
 	QRegularExpression rx("\\d{1,5}x\\d{1,5}");
 	QValidator *validator = new QRegularExpressionValidator(rx, this);
@@ -934,6 +937,8 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 
 	connect(ui->useStreamKeyAdv, SIGNAL(clicked()), this,
 		SLOT(UseStreamKeyAdvClicked()));
+
+	UpdateAudioWarnings();
 }
 
 OBSBasicSettings::~OBSBasicSettings()
@@ -2536,6 +2541,8 @@ void OBSBasicSettings::LoadAudioSettings()
 		config_get_double(main->Config(), "Audio", "MeterDecayRate");
 	uint32_t peakMeterTypeIdx =
 		config_get_uint(main->Config(), "Audio", "PeakMeterType");
+	bool enableLLAudioBuffering = config_get_bool(
+		GetGlobalConfig(), "Audio", "LowLatencyAudioBuffering");
 
 	loading = true;
 
@@ -2572,6 +2579,7 @@ void OBSBasicSettings::LoadAudioSettings()
 		ui->meterDecayRate->setCurrentIndex(0);
 
 	ui->peakMeterType->setCurrentIndex(peakMeterTypeIdx);
+	ui->lowLatencyBuffering->setChecked(enableLLAudioBuffering);
 
 	LoadAudioDevices();
 	LoadAudioSources();
@@ -3754,6 +3762,14 @@ void OBSBasicSettings::SaveAudioSettings()
 		main->UpdateVolumeControlsPeakMeterType();
 	}
 
+	if (WidgetChanged(ui->lowLatencyBuffering)) {
+		bool enableLLAudioBuffering =
+			ui->lowLatencyBuffering->isChecked();
+		config_set_bool(GetGlobalConfig(), "Audio",
+				"LowLatencyAudioBuffering",
+				enableLLAudioBuffering);
+	}
+
 	for (auto &audioSource : audioSources) {
 		auto source = OBSGetStrongRef(get<0>(audioSource));
 		if (!source)
@@ -4287,9 +4303,12 @@ void OBSBasicSettings::AudioChangedRestart()
 	if (!loading) {
 		int currentChannelIndex = ui->channelSetup->currentIndex();
 		int currentSampleRateIndex = ui->sampleRate->currentIndex();
+		bool currentLLAudioBufVal =
+			ui->lowLatencyBuffering->isChecked();
 
 		if (currentChannelIndex != channelIndex ||
-		    currentSampleRateIndex != sampleRateIndex) {
+		    currentSampleRateIndex != sampleRateIndex ||
+		    currentLLAudioBufVal != llBufferingEnabled) {
 			audioChanged = true;
 			ui->audioMsg->setText(
 				QTStr("Basic.Settings.ProgramRestart"));
@@ -4318,13 +4337,9 @@ void OBSBasicSettings::SpeakerLayoutChanged(int idx)
 	bool surround = IsSurround(speakerLayout.c_str());
 
 	if (surround) {
-		QString warning = QTStr(MULTI_CHANNEL_WARNING ".Enabled") +
-				  QStringLiteral("\n\n") +
-				  QTStr(MULTI_CHANNEL_WARNING);
 		/*
 		 * Display all bitrates
 		 */
-		ui->audioMsg_2->setText(warning);
 		PopulateAACBitrates(
 			{ui->simpleOutputABitrate, ui->advOutTrack1Bitrate,
 			 ui->advOutTrack2Bitrate, ui->advOutTrack3Bitrate,
@@ -4335,7 +4350,6 @@ void OBSBasicSettings::SpeakerLayoutChanged(int idx)
 		 * Reset audio bitrate for simple and adv mode, update list of
 		 * bitrates and save setting.
 		 */
-		ui->audioMsg_2->setText(QString());
 		RestrictResetBitrates(
 			{ui->simpleOutputABitrate, ui->advOutTrack1Bitrate,
 			 ui->advOutTrack2Bitrate, ui->advOutTrack3Bitrate,
@@ -4351,6 +4365,8 @@ void OBSBasicSettings::SpeakerLayoutChanged(int idx)
 		SaveCombo(ui->advOutTrack5Bitrate, "AdvOut", "Track5Bitrate");
 		SaveCombo(ui->advOutTrack6Bitrate, "AdvOut", "Track6Bitrate");
 	}
+
+	UpdateAudioWarnings();
 }
 
 void OBSBasicSettings::HideOBSWindowWarning(int state)
@@ -5257,6 +5273,56 @@ void OBSBasicSettings::SurroundWarning(int idx)
 	lastChannelSetupIdx = idx;
 }
 
+#define LL_BUFFERING_WARNING "Basic.Settings.Audio.LowLatencyBufferingWarning"
+
+void OBSBasicSettings::UpdateAudioWarnings()
+{
+	QString speakerLayoutQstr = ui->channelSetup->currentText();
+	bool surround = IsSurround(QT_TO_UTF8(speakerLayoutQstr));
+	bool lowBufferingActive = ui->lowLatencyBuffering->isChecked();
+
+	QString text;
+
+	if (surround) {
+		text = QTStr(MULTI_CHANNEL_WARNING ".Enabled") +
+		       QStringLiteral("\n\n") + QTStr(MULTI_CHANNEL_WARNING);
+	}
+
+	if (lowBufferingActive) {
+		if (!text.isEmpty())
+			text += QStringLiteral("\n\n");
+
+		text += QTStr(LL_BUFFERING_WARNING ".Enabled") +
+			QStringLiteral("\n\n") + QTStr(LL_BUFFERING_WARNING);
+	}
+
+	ui->audioMsg_2->setText(text);
+}
+
+void OBSBasicSettings::LowLatencyBufferingChanged(bool checked)
+{
+	if (checked) {
+		QString warningStr = QTStr(LL_BUFFERING_WARNING) +
+				     QStringLiteral("\n\n") +
+				     QTStr(LL_BUFFERING_WARNING ".Confirm");
+
+		auto button = OBSMessageBox::question(
+			this, QTStr(LL_BUFFERING_WARNING ".Title"), warningStr);
+
+		if (button == QMessageBox::No) {
+			QMetaObject::invokeMethod(ui->lowLatencyBuffering,
+						  "setChecked",
+						  Qt::QueuedConnection,
+						  Q_ARG(bool, false));
+			return;
+		}
+	}
+
+	QMetaObject::invokeMethod(this, "UpdateAudioWarnings",
+				  Qt::QueuedConnection);
+	QMetaObject::invokeMethod(this, "AudioChangedRestart");
+}
+
 void OBSBasicSettings::SimpleRecordingQualityLosslessWarning(int idx)
 {
 	if (idx == lastSimpleRecQualityIdx || idx == -1)

UI/window-basic-settings.hpp

@@ -120,6 +120,7 @@ private:
 	std::string savedTheme;
 	int sampleRateIndex = 0;
 	int channelIndex = 0;
+	bool llBufferingEnabled = false;
 
 	int lastSimpleRecQualityIdx = 0;
 	int lastServiceIdx = -1;
@@ -379,6 +380,8 @@ private slots:
 	void ReloadAudioSources();
 	void SurroundWarning(int idx);
 	void SpeakerLayoutChanged(int idx);
+	void LowLatencyBufferingChanged(bool checked);
+	void UpdateAudioWarnings();
 	void OutputsChanged();
 	void Stream1Changed();
 	void VideoChanged();