obs-webrtc: Add Simulcast Support

UI/data/locale/en-US.ini

@@ -985,6 +985,9 @@ Basic.Settings.Stream.MultitrackVideoStreamDumpEnable="Enable stream dump to FLV
 Basic.Settings.Stream.MultitrackVideoConfigOverride="Config Override (JSON)"
 Basic.Settings.Stream.MultitrackVideoConfigOverrideEnable="Enable Config Override"
 Basic.Settings.Stream.MultitrackVideoLabel="Multitrack Video"
+Basic.Settings.Stream.SimulcastLabel="Simulcast"
+Basic.Settings.Stream.SimulcastInfo="Simulcast allows you to encode and send multiple video qualities."
+Basic.Settings.Stream.SimulcastTotalLayers="Total Layers"
 Basic.Settings.Stream.AdvancedOptions="Advanced Options"
 
 # basic mode 'output' settings

UI/forms/OBSBasicSettings.ui

@@ -1849,6 +1849,91 @@
                 </layout>
                </widget>
               </item>
+              <item>
+               <widget class="QGroupBox" name="simulcastGroupBox">
+                <property name="title">
+                 <string>Basic.Settings.Stream.SimulcastLabel</string>
+                </property>
+                <layout class="QVBoxLayout" name="verticalLayout_35">
+                 <property name="leftMargin">
+                  <number>9</number>
+                 </property>
+                 <property name="topMargin">
+                  <number>2</number>
+                 </property>
+                 <property name="rightMargin">
+                  <number>9</number>
+                 </property>
+                 <property name="bottomMargin">
+                  <number>9</number>
+                 </property>
+                 <item>
+                  <layout class="QHBoxLayout" name="horizontalLayout_33">
+                   <item>
+                    <spacer name="horizontalSpacer_33">
+                     <property name="orientation">
+                      <enum>Qt::Horizontal</enum>
+                     </property>
+                     <property name="sizeType">
+                      <enum>QSizePolicy::Fixed</enum>
+                     </property>
+                     <property name="sizeHint" stdset="0">
+                      <size>
+                       <width>170</width>
+                       <height>10</height>
+                      </size>
+                     </property>
+                    </spacer>
+                   </item>
+                   <item>
+                    <widget class="QLabel" name="simulcastInfo">
+                     <property name="text">
+                      <string>Basic.Settings.Stream.SimulcastInfo</string>
+                     </property>
+                     <property name="textFormat">
+                      <enum>Qt::RichText</enum>
+                     </property>
+                     <property name="wordWrap">
+                      <bool>true</bool>
+                     </property>
+                    </widget>
+                   </item>
+                  </layout>
+                 </item>
+                 <item>
+                  <layout class="QFormLayout" name="formLayout_39">
+                   <property name="fieldGrowthPolicy">
+                    <enum>QFormLayout::AllNonFixedFieldsGrow</enum>
+                   </property>
+                   <item row="1" column="0">
+                    <widget class="QLabel" name="simulcastTotalLayersLabel">
+                     <property name="text">
+                      <string>Basic.Settings.Stream.SimulcastTotalLayers</string>
+                     </property>
+                    </widget>
+                   </item>
+                   <item row="1" column="1">
+                    <layout class="QHBoxLayout" name="horizontalLayout_34" stretch="0,0">
+                     <item>
+                      <widget class="QSpinBox" name="simulcastTotalLayers">
+                       <property name="minimum">
+                        <number>1</number>
+                       </property>
+                       <property name="maximum">
+                        <number>4</number>
+                       </property>
+                       <property name="value">
+                        <number>1</number>
+                       </property>
+                      </widget>
+                     </item>
+                    </layout>
+                   </item>
+                  </layout>
+                 </item>
+                </layout>
+               </widget>
+              </item>
               <item>
                <widget class="QGroupBox" name="serviceAdvancedOptionsGroupBox">
                 <property name="title">

UI/simulcast-encoders.hpp

@@ -0,0 +1,69 @@
+#pragma once
+
+struct SimulcastEncoders {
+public:
+	void Create(const char *encoderId, OBSBasic *main)
+	{
+		int rescaleFilter = config_get_int(main->Config(), "AdvOut", "RescaleFilter");
+		if (rescaleFilter == OBS_SCALE_DISABLE) {
+			rescaleFilter = OBS_SCALE_BICUBIC;
+		}
+
+		std::string encoder_name = "simulcast_0";
+		auto simulcastTotalLayers = config_get_int(main->Config(), "Stream1", "SimulcastTotalLayers");
+		if (simulcastTotalLayers <= 1) {
+			return;
+		}
+
+		auto widthStep = video_output_get_width(obs_get_video()) / simulcastTotalLayers;
+		auto heightStep = video_output_get_height(obs_get_video()) / simulcastTotalLayers;
+
+		for (auto i = simulcastTotalLayers - 1; i > 0; i--) {
+			uint32_t width = widthStep * i;
+			width -= width % 2;
+
+			uint32_t height = heightStep * i;
+			height -= height % 2;
+
+			encoder_name[encoder_name.size() - 1] = std::to_string(i).at(0);
+			auto simulcast_encoder =
+				obs_video_encoder_create(encoderId, encoder_name.c_str(), nullptr, nullptr);
+
+			if (simulcast_encoder) {
+				obs_encoder_set_video(simulcast_encoder, obs_get_video());
+				obs_encoder_set_scaled_size(simulcast_encoder, width, height);
+				obs_encoder_set_gpu_scale_type(simulcast_encoder, (obs_scale_type)rescaleFilter);
+				simulcastEncoders.push_back(simulcast_encoder);
+				obs_encoder_release(simulcast_encoder);
+			} else {
+				blog(LOG_WARNING,
+				     "Failed to create video streaming simulcast encoders (BasicOutputHandler)");
+			}
+		}
+	}
+
+	void Update(obs_data_t *videoSettings, int videoBitrate)
+	{
+		auto bitrateStep = videoBitrate / static_cast<int>(simulcastEncoders.size() + 1);
+		for (auto &simulcastEncoder : simulcastEncoders) {
+			videoBitrate -= bitrateStep;
+			obs_data_set_int(videoSettings, "bitrate", videoBitrate);
+			obs_encoder_update(simulcastEncoder, videoSettings);
+		}
+	}
+
+	void SetVideoFormat(enum video_format format)
+	{
+		for (auto enc : simulcastEncoders)
+			obs_encoder_set_preferred_video_format(enc, format);
+	}
+
+	void SetStreamOutput(obs_output_t *streamOutput)
+	{
+		for (size_t i = 0; i < simulcastEncoders.size(); i++)
+			obs_output_set_video_encoder2(streamOutput, simulcastEncoders[i], i + 1);
+	}
+
+private:
+	std::vector<OBSEncoder> simulcastEncoders;
+};

UI/window-basic-main-outputs.cpp

@@ -305,6 +305,10 @@ inline BasicOutputHandler::BasicOutputHandler(OBSBasic *main_) : main(main_)
 	}
 	if (multitrack_enabled)
 		multitrackVideo = make_unique<MultitrackVideoOutput>();
+
+	if (config_get_int(main->Config(), "Stream1", "SimulcastTotalLayers") > 1) {
+		simulcastEncoders = make_unique<SimulcastEncoders>();
+	};
 }
 
 extern void log_vcam_changed(const VCamConfig &config, bool starting);
@@ -541,6 +545,10 @@ void SimpleOutput::LoadStreamingPreset_Lossy(const char *encoderId)
 	if (!videoStreaming)
 		throw "Failed to create video streaming encoder (simple output)";
 	obs_encoder_release(videoStreaming);
+
+	if (simulcastEncoders != nullptr) {
+		simulcastEncoders->Create(encoderId, main);
+	}
 }
 
 /* mistakes have been made to lead us to this. */
@@ -800,11 +808,18 @@ void SimpleOutput::Update()
 		break;
 	default:
 		obs_encoder_set_preferred_video_format(videoStreaming, VIDEO_FORMAT_NV12);
+		if (simulcastEncoders != nullptr) {
+			simulcastEncoders->SetVideoFormat(VIDEO_FORMAT_NV12);
+		}
 	}
 
 	obs_encoder_update(videoStreaming, videoSettings);
 	obs_encoder_update(audioStreaming, audioSettings);
 	obs_encoder_update(audioArchive, audioSettings);
+
+	if (simulcastEncoders != nullptr) {
+		simulcastEncoders->Update(videoSettings, videoBitrate);
+	}
 }
 
 void SimpleOutput::UpdateRecordingAudioSettings()
@@ -1094,6 +1109,9 @@ std::shared_future<void> SimpleOutput::SetupStreaming(obs_service_t *service, Se
 		}
 
 		obs_output_set_video_encoder(streamOutput, videoStreaming);
+		if (simulcastEncoders != nullptr) {
+			simulcastEncoders->SetStreamOutput(streamOutput);
+		}
 		obs_output_set_audio_encoder(streamOutput, audioStreaming, 0);
 		obs_output_set_service(streamOutput, service);
 		return true;
@@ -1568,6 +1586,9 @@ AdvancedOutput::AdvancedOutput(OBSBasic *main_) : BasicOutputHandler(main_)
 		throw "Failed to create streaming video encoder "
 		      "(advanced output)";
 	obs_encoder_release(videoStreaming);
+	if (simulcastEncoders != nullptr) {
+		simulcastEncoders->Create(streamEncoder, main);
+	}
 
 	const char *rate_control =
 		obs_data_get_string(useStreamEncoder ? streamEncSettings : recordEncSettings, "rate_control");
@@ -1668,6 +1689,9 @@ void AdvancedOutput::UpdateStreamSettings()
 	}
 
 	obs_encoder_update(videoStreaming, settings);
+	if (simulcastEncoders != nullptr) {
+		simulcastEncoders->Update(settings, obs_data_get_int(settings, "bitrate"));
+	}
 }
 
 inline void AdvancedOutput::UpdateRecordingSettings()
@@ -2082,6 +2106,9 @@ std::shared_future<void> AdvancedOutput::SetupStreaming(obs_service_t *service,
 		}
 
 		obs_output_set_video_encoder(streamOutput, videoStreaming);
+		if (simulcastEncoders != nullptr) {
+			simulcastEncoders->SetStreamOutput(streamOutput);
+		}
 		obs_output_set_audio_encoder(streamOutput, streamAudioEnc, 0);
 
 		if (!is_multitrack_output) {

UI/window-basic-main-outputs.hpp

@@ -5,6 +5,7 @@
 #include <string>
 
 #include "multitrack-video-output.hpp"
+#include "simulcast-encoders.hpp"
 
 class OBSBasic;
 
@@ -37,6 +38,8 @@ struct BasicOutputHandler {
 	obs_scene_t *vCamSourceScene = nullptr;
 	obs_sceneitem_t *vCamSourceSceneItem = nullptr;
 
+	std::unique_ptr<SimulcastEncoders> simulcastEncoders;
+
 	std::string outputType;
 	std::string lastError;
 
@@ -99,6 +102,8 @@ struct BasicOutputHandler {
 						      size_t main_audio_mixer, std::optional<size_t> vod_track_mixer,
 						      std::function<void(std::optional<bool>)> continuation);
 	OBSDataAutoRelease GenerateMultitrackVideoStreamDumpConfig();
+	void CreateSimulcastEncoders(const char *encoderId);
+	void SimulcastEncodersUpdate(obs_data_t *videoSettings, int videoBitrate);
 };
 
 BasicOutputHandler *CreateSimpleOutputHandler(OBSBasic *main);

UI/window-basic-settings-stream.cpp

@@ -102,6 +102,7 @@ void OBSBasicSettings::InitStreamPage()
 void OBSBasicSettings::LoadStream1Settings()
 {
 	bool ignoreRecommended = config_get_bool(main->Config(), "Stream1", "IgnoreRecommended");
+	int simulcastTotalLayers = config_get_int(main->Config(), "Stream1", "SimulcastTotalLayers");
 
 	obs_service_t *service_obj = main->GetService();
 	const char *type = obs_service_get_type(service_obj);
@@ -198,10 +199,13 @@ void OBSBasicSettings::LoadStream1Settings()
 	if (use_custom_server)
 		ui->serviceCustomServer->setText(server);
 
-	if (is_whip)
+	if (is_whip) {
 		ui->key->setText(bearer_token);
-	else
+		ui->simulcastGroupBox->show();
+	} else {
 		ui->key->setText(key);
+		ui->simulcastGroupBox->hide();
+	}
 
 	ServiceChanged(true);
 
@@ -215,6 +219,7 @@ void OBSBasicSettings::LoadStream1Settings()
 	ui->streamPage->setEnabled(!streamActive);
 
 	ui->ignoreRecommended->setChecked(ignoreRecommended);
+	ui->simulcastTotalLayers->setValue(simulcastTotalLayers);
 
 	loading = false;
 
@@ -316,6 +321,9 @@ void OBSBasicSettings::SaveStream1Settings()
 
 	SaveCheckBox(ui->ignoreRecommended, "Stream1", "IgnoreRecommended");
 
+	auto oldSimulcastTotalLayers = config_get_int(main->Config(), "Stream1", "SimulcastTotalLayers");
+	SaveSpinBox(ui->simulcastTotalLayers, "Stream1", "SimulcastTotalLayers");
+
 	auto oldMultitrackVideoSetting = config_get_bool(main->Config(), "Stream1", "EnableMultitrackVideo");
 
 	if (!IsCustomService()) {
@@ -343,7 +351,8 @@ void OBSBasicSettings::SaveStream1Settings()
 	SaveCheckBox(ui->multitrackVideoConfigOverrideEnable, "Stream1", "MultitrackVideoConfigOverrideEnabled");
 	SaveText(ui->multitrackVideoConfigOverride, "Stream1", "MultitrackVideoConfigOverride");
 
-	if (oldMultitrackVideoSetting != ui->enableMultitrackVideo->isChecked())
+	if (oldMultitrackVideoSetting != ui->enableMultitrackVideo->isChecked() ||
+	    oldSimulcastTotalLayers != ui->simulcastTotalLayers->value())
 		main->ResetOutputs();
 
 	SwapMultiTrack(QT_TO_UTF8(protocol));
@@ -576,6 +585,12 @@ void OBSBasicSettings::on_service_currentIndexChanged(int idx)
 	} else {
 		SwapMultiTrack(QT_TO_UTF8(protocol));
 	}
+
+	if (IsWHIP()) {
+		ui->simulcastGroupBox->show();
+	} else {
+		ui->simulcastGroupBox->hide();
+	}
 }
 
 void OBSBasicSettings::on_customServer_textChanged(const QString &)

UI/window-basic-settings.cpp

@@ -407,6 +407,7 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 	HookWidget(ui->authUsername,         EDIT_CHANGED,   STREAM1_CHANGED);
 	HookWidget(ui->authPw,               EDIT_CHANGED,   STREAM1_CHANGED);
 	HookWidget(ui->ignoreRecommended,    CHECK_CHANGED,  STREAM1_CHANGED);
+	HookWidget(ui->simulcastTotalLayers, SCROLL_CHANGED, STREAM1_CHANGED);
 	HookWidget(ui->enableMultitrackVideo,      CHECK_CHANGED,  STREAM1_CHANGED);
 	HookWidget(ui->multitrackVideoMaximumAggregateBitrateAuto, CHECK_CHANGED,  STREAM1_CHANGED);
 	HookWidget(ui->multitrackVideoMaximumAggregateBitrate,     SCROLL_CHANGED, STREAM1_CHANGED);

plugins/obs-webrtc/data/locale/en-US.ini

@@ -4,3 +4,4 @@ Service.BearerToken="Bearer Token"
 
 Error.InvalidSDP="WHIP server responded with invalid SDP: %1"
 Error.NoRemoteDescription="Failed to set remote description: %1"
+Error.SimulcastLayersRejected="WHIP server only accepted %1 simulcast layers"