Add support in "macOS ScreenCapture" for capturing audio through ScreenCaptureKit in macOS 13. By default, OBS will capture the audio for the frame content its capturing and exclude OBS own audio. For additional information

on the capabilities of audio capture refer to the documentation https://developer.apple.com/documentation/screencapturekit/ or watch the session "Meet ScreenCaptureKit".

Currently audio capture typically happens via virtual devices set up with 3rd party products. This requires additional installation and configuration by users.
Including the audio with the existing CMBuffers will make it easier to manage audio sync with video frames. Additionally, you can capture distinct audio tracks from multiple apps at once,
like a call with friends +  screen content.

macOS 13 on a 2019 16" MacBook Pro
macOS 13 on a 2022 M1 Pro Macbook Pro

Tested with multiple games + Discord, FaceTime, Apple Music and Safari tabs playing audio content.

* Bug fix (non-breaking change which fixes an issue)
* Performance enhancement (non-breaking change which improves efficiency)

* Additional control over what audio content to capture
* Logic to manage audio & frame sync

plugins/mac-capture/mac-screen-capture.m

@@ -152,8 +152,8 @@ static void screen_capture_destroy(void *data)
 	bfree(sc);
 }
 
-static inline void screen_stream_update(struct screen_capture *sc,
-					CMSampleBufferRef sample_buffer)
+static inline void screen_stream_video_update(struct screen_capture *sc,
+					      CMSampleBufferRef sample_buffer)
 {
 	bool frame_detail_errored = false;
 	float scale_factor = 1.0f;
@@ -290,6 +290,48 @@ static inline void screen_stream_update(struct screen_capture *sc,
 	}
 }
 
+static inline void screen_stream_audio_update(struct screen_capture *sc,
+					      CMSampleBufferRef sample_buffer)
+{
+	CMFormatDescriptionRef format_description =
+		CMSampleBufferGetFormatDescription(sample_buffer);
+	const AudioStreamBasicDescription *audio_description =
+		CMAudioFormatDescriptionGetStreamBasicDescription(
+			format_description);
+
+	char *_Nullable bytes = NULL;
+	CMBlockBufferRef data_buffer =
+		CMSampleBufferGetDataBuffer(sample_buffer);
+	size_t data_buffer_length = CMBlockBufferGetDataLength(data_buffer);
+	CMBlockBufferGetDataPointer(data_buffer, 0, &data_buffer_length, NULL,
+				    &bytes);
+
+	CMTime presentation_time =
+		CMSampleBufferGetOutputPresentationTimeStamp(sample_buffer);
+
+	struct obs_source_audio audio_data = {};
+
+	for (uint32_t channel_idx = 0;
+	     channel_idx < audio_description->mChannelsPerFrame;
+	     ++channel_idx) {
+		uint32_t offset =
+			(uint32_t)(data_buffer_length /
+				   audio_description->mChannelsPerFrame) *
+			channel_idx;
+		audio_data.data[channel_idx] = (uint8_t *)bytes + offset;
+	}
+
+	audio_data.frames = (uint32_t)(data_buffer_length /
+				       audio_description->mBytesPerFrame /
+				       audio_description->mChannelsPerFrame);
+	audio_data.speakers = audio_description->mChannelsPerFrame;
+	audio_data.samples_per_sec = audio_description->mSampleRate;
+	audio_data.timestamp =
+		CMTimeGetSeconds(presentation_time) * NSEC_PER_SEC;
+	audio_data.format = AUDIO_FORMAT_FLOAT_PLANAR;
+	obs_source_output_audio(sc->source, &audio_data);
+}
+
 static bool init_screen_stream(struct screen_capture *sc)
 {
 	SCContentFilter *content_filter;
@@ -370,6 +412,16 @@ static bool init_screen_stream(struct screen_capture *sc)
 	[sc->stream_properties setQueueDepth:8];
 	[sc->stream_properties setShowsCursor:!sc->hide_cursor];
 	[sc->stream_properties setPixelFormat:'BGRA'];
+#if __MAC_OS_X_VERSION_MAX_ALLOWED >= 130000
+	if (@available(macOS 13.0, *)) {
+		[sc->stream_properties setCapturesAudio:TRUE];
+		[sc->stream_properties setExcludesCurrentProcessAudio:TRUE];
+		[sc->stream_properties setChannelCount:2];
+	}
+#endif
+	sc->disp = [[SCStream alloc] initWithFilter:content_filter
+				      configuration:sc->stream_properties
+					   delegate:nil];
 
 	switch (sc->capture_type) {
 	case ScreenCaptureDisplayStream:
@@ -415,6 +467,24 @@ static bool init_screen_stream(struct screen_capture *sc)
 		return !did_add_output;
 	}
 
+#if __MAC_OS_X_VERSION_MAX_ALLOWED >= 130000
+	if (__builtin_available(macOS 13.0, *)) {
+		did_add_output = [sc->disp
+			   addStreamOutput:sc->capture_delegate
+				      type:SCStreamOutputTypeAudio
+			sampleHandlerQueue:nil
+				     error:&error];
+		if (!did_add_output) {
+			MACCAP_ERR(
+				"init_screen_stream: Failed to add audio stream output with error %s\n",
+				[[error localizedFailureReason]
+					cStringUsingEncoding:
+						NSUTF8StringEncoding]);
+			[error release];
+			return !did_add_output;
+		}
+	}
+#endif
 	os_event_init(&sc->disp_finished, OS_EVENT_TYPE_MANUAL);
 	os_event_init(&sc->stream_start_completed, OS_EVENT_TYPE_MANUAL);
 
@@ -946,7 +1016,8 @@ struct obs_source_info screen_capture_info = {
 	.destroy = screen_capture_destroy,
 
 	.output_flags = OBS_SOURCE_VIDEO | OBS_SOURCE_CUSTOM_DRAW |
-			OBS_SOURCE_DO_NOT_DUPLICATE | OBS_SOURCE_SRGB,
+			OBS_SOURCE_DO_NOT_DUPLICATE | OBS_SOURCE_SRGB |
+			OBS_SOURCE_AUDIO,
 	.video_tick = screen_capture_video_tick,
 	.video_render = screen_capture_video_render,
 
@@ -966,7 +1037,17 @@ struct obs_source_info screen_capture_info = {
 		       ofType:(SCStreamOutputType)type
 {
 	if (self.sc != NULL) {
-		screen_stream_update(self.sc, sampleBuffer);
+		if (type == SCStreamOutputTypeScreen) {
+			screen_stream_video_update(self.sc, sampleBuffer);
+		}
+#if __MAC_OS_X_VERSION_MAX_ALLOWED >= 130000
+		else if (@available(macOS 13.0, *)) {
+			if (type == SCStreamOutputTypeAudio) {
+				screen_stream_audio_update(self.sc,
+							   sampleBuffer);
+			}
+		}
+#endif
 	}
 }