win-dshow: Improve automatic Elgato audio device selection

Implement automatic audio device selection for devices that use two
separate DirectShow filters for audio and video instead of having a
single filter with audio and video output pins.

Please note that this fix is currently only active for Elgato USB and
PCIe devices (e.g. Cam Link, HD60 S, HD60 Pro, 4K60 Pro) to avoid
unintentionally changing the behavior for any other devices (e.g.
webcams).

(Jim edit: This fixes an issue with newer Elgato devices where the
devices would not automatically have their audio coupled with the video;
users would have to manually select the audio device in order to get
audio functioning.)

Closes jp9000/obs-studio#1081

plugins/win-dshow/libdshowcapture

@@ -1 +1 @@
-Subproject commit 4a518720f5ee3f1f58ca416fc57c114acb9b22c6
+Subproject commit cba07c63810f51a58f6fb7f2e3b0fb162b5a6313

plugins/win-dshow/win-dshow.cpp

@@ -165,6 +165,7 @@ struct DShowInput {
 	Device       device;
 	bool         deactivateWhenNotShowing = false;
 	bool         deviceHasAudio = false;
+	bool         deviceHasSeparateAudioFilter = false;
 	bool         flip = false;
 	bool         active = false;
 
@@ -845,6 +846,7 @@ bool DShowInput::UpdateVideoConfig(obs_data_t *settings)
 	videoConfig.internalFormat   = format;
 
 	deviceHasAudio = dev.audioAttached;
+	deviceHasSeparateAudioFilter = dev.separateAudioFilter;
 
 	videoConfig.callback = std::bind(&DShowInput::OnVideoData, this,
 			placeholders::_1, placeholders::_2,
@@ -921,7 +923,8 @@ bool DShowInput::UpdateAudioConfig(obs_data_t *settings)
 		return true;
 	}
 
-	audioConfig.useVideoDevice = !useCustomAudio;
+	audioConfig.useVideoDevice = !useCustomAudio && !deviceHasSeparateAudioFilter;
+	audioConfig.useSeparateAudioFilter = deviceHasSeparateAudioFilter;
 
 	audioConfig.callback = std::bind(&DShowInput::OnAudioData, this,
 			placeholders::_1, placeholders::_2,
@@ -942,8 +945,12 @@ bool DShowInput::UpdateAudioConfig(obs_data_t *settings)
 	blog(LOG_INFO, "\tusing video device audio: %s",
 			audioConfig.useVideoDevice ? "yes" : "no");
 
-	if (!audioConfig.useVideoDevice)
-		blog(LOG_INFO, "\taudio device: %s", (const char*)name_utf8);
+	if (!audioConfig.useVideoDevice) {
+		if (audioConfig.useSeparateAudioFilter)
+			blog(LOG_INFO, "\tseparate audio filter");
+		else
+			blog(LOG_INFO, "\taudio device: %s", (const char*)name_utf8);
+	}
 
 	const char *mode = "";