source-mirror: Fix potential lockup and rescaling with original size

Getting the resolution of a source is very expensive in libOBS, as libOBS does not cache it and instead always calls into the filters and sources to determine the actual source. This also leads to potential lockups due to the filter list mutex being locked for the target source.

Therefore instead of calling it multiple times, cache the result of the call, if that result is even necessary. This reduces the need to synchronize lightly parallelized work (UI and libOBS code) and helps against the potential race condition in libOBS.

source/sources/source-mirror.cpp

@@ -142,20 +142,12 @@ source::mirror::mirror_instance::~mirror_instance()
 
 uint32_t source::mirror::mirror_instance::get_width()
 {
-	if (!_source || !_source_item || !(obs_source_get_output_flags(_source->get()) & OBS_SOURCE_VIDEO))
+	return _source_size.first;
-		return 0;
-	if (_rescale_enabled && _rescale_width > 0 && !_rescale_keep_orig_size)
-		return _rescale_width;
-	return _source->width();
 }
 
 uint32_t source::mirror::mirror_instance::get_height()
 {
-	if (!_source || !_source_item || !(obs_source_get_output_flags(_source->get()) & OBS_SOURCE_VIDEO))
+	return _source_size.second;
-		return 0;
-	if (_rescale_enabled && _rescale_height > 0 && !_rescale_keep_orig_size)
-		return _rescale_height;
-	return _source->height();
 }
 
 static void convert_config(obs_data_t* data)
@@ -242,21 +234,28 @@ void source::mirror::mirror_instance::save(obs_data_t* data)
 
 void source::mirror::mirror_instance::video_tick(float time)
 {
+	if (_source && ((obs_source_get_output_flags(_source->get()) & OBS_SOURCE_VIDEO) != 0)) {
+		if (_rescale_keep_orig_size || !_rescale_enabled) {
+			_source_size.first  = _source->width();
+			_source_size.second = _source->height();
+		} else {
+			_source_size.first  = _rescale_width;
+			_source_size.second = _rescale_height;
+		}
+	} else {
+		_source_size.first  = 0;
+		_source_size.second = 0;
+	}
+
 	if (_source_item && ((obs_source_get_output_flags(_source->get()) & OBS_SOURCE_VIDEO) != 0)) {
 		obs_transform_info info;
 
-		/// Position, Rotation, Scale, Alignment
+		/// Position, Rotation, Scale, Alignment, Bounding Box
 		vec2_set(&info.pos, 0, 0);
 		info.rot = 0;
 		vec2_set(&info.scale, 1., 1.);
 		info.alignment = OBS_ALIGN_LEFT | OBS_ALIGN_TOP;
-
+		vec2_set(&info.bounds, static_cast<float_t>(_source_size.first), static_cast<float_t>(_source_size.second));
-		/// Bounding Box
-		if (_rescale_enabled && _rescale_keep_orig_size) {
-			vec2_set(&info.bounds, static_cast<float_t>(_rescale_width), static_cast<float_t>(_rescale_height));
-		} else {
-			vec2_set(&info.bounds, static_cast<float_t>(get_width()), static_cast<float_t>(get_height()));
-		}
 
 		info.bounds_alignment = _rescale_alignment;
 		info.bounds_type      = OBS_BOUNDS_STRETCH;
@@ -284,18 +283,11 @@ void source::mirror::mirror_instance::video_render(gs_effect_t* effect)
 	// Rendering depends on cached or uncached.
 	if (_cache_enabled || _rescale_enabled) {
 		if (!_cache_rendered) {
-			uint32_t width  = get_width();
+			if (!_source_size.first || !_source_size.second)
-			uint32_t height = get_height();
-			if (_rescale_enabled) {
-				width  = _rescale_width;
-				height = _rescale_height;
-			}
-
-			if (!width || !height)
 				return;
 
 			try {
-				_cache_texture  = this->_cache_renderer->render(width, height);
+				_cache_texture  = this->_cache_renderer->render(_source_size.first, _source_size.second);
 				_cache_rendered = true;
 			} catch (...) {
 			}
@@ -310,7 +302,7 @@ void source::mirror::mirror_instance::video_render(gs_effect_t* effect)
 		GS_DEBUG_MARKER_BEGIN(GS_DEBUG_COLOR_ITEM_TEXTURE, "render_cache");
 		gs_effect_set_texture(gs_effect_get_param_by_name(effect, "image"), _cache_texture->get_object());
 		while (gs_effect_loop(effect, "Draw")) {
-			gs_draw_sprite(nullptr, 0, get_width(), get_height());
+			gs_draw_sprite(nullptr, 0, _source_size.first, _source_size.second);
 		}
 		GS_DEBUG_MARKER_END();
 	} else {
@@ -320,7 +312,8 @@ void source::mirror::mirror_instance::video_render(gs_effect_t* effect)
 	GS_DEBUG_MARKER_END();
 }
 
-void source::mirror::mirror_instance::audio_output_cb() noexcept try {
+void source::mirror::mirror_instance::audio_output_cb() noexcept
+try {
 	std::unique_lock<std::mutex> ulock(this->_audio_lock_outputter);
 
 	while (!this->_audio_kill_thread) {
@@ -359,9 +352,9 @@ void source::mirror::mirror_instance::audio_output_cb() noexcept try {
 
 void source::mirror::mirror_instance::enum_active_sources(obs_source_enum_proc_t enum_callback, void* param)
 {
-	if (_scene) {
+	/*	if (_scene) {
 		enum_callback(_self, _scene.get(), param);
-	}
+	}*/
 	if (_source) {
 		enum_callback(_self, _source->get(), param);
 	}
@@ -369,9 +362,9 @@ void source::mirror::mirror_instance::enum_active_sources(obs_source_enum_proc_t
 
 void source::mirror::mirror_instance::enum_all_sources(obs_source_enum_proc_t enum_callback, void* param)
 {
-	if (_scene) {
+	/*	if (_scene) {
 		enum_callback(_self, _scene.get(), param);
-	}
+	}*/
 	if (_source) {
 		enum_callback(_self, _source->get(), param);
 	}
@@ -479,7 +472,8 @@ void source::mirror::mirror_factory::get_defaults2(obs_data_t* data)
 	obs_data_set_default_int(data, ST_SCALING_ALIGNMENT, OBS_ALIGN_CENTER);
 }
 
-static bool modified_properties(obs_properties_t* pr, obs_property_t* p, obs_data_t* data) noexcept try {
+static bool modified_properties(obs_properties_t* pr, obs_property_t* p, obs_data_t* data) noexcept
+try {
 	if (obs_properties_get(pr, ST_SOURCE) == p) {
 		obs_source_t* target = obs_get_source_by_name(obs_data_get_string(data, ST_SOURCE));
 		if (target) {

source/sources/source-mirror.hpp

@@ -53,6 +53,9 @@ namespace source {
 			std::shared_ptr<obs::source> _source;
 			std::string                  _source_name;
 
+			// Cached Data
+			std::pair<uint32_t, uint32_t> _source_size;
+
 			// Audio
 			bool                                           _audio_enabled;
 			speaker_layout                                 _audio_layout;