NDI cleanup to avoid calling NDI while holding the output mutex

src/video/ndi/NdiOutput.h

@@ -30,13 +30,13 @@ public:
 	NdiOutputMetrics Metrics() const override;
 
 private:
-	void CompletePendingLocked(VideoIOCompletionResult result);
-	void FlushPendingLocked();
+	void CompleteBuffer(void* buffer, VideoIOCompletionResult result);
 	static void PopulateState(VideoIOState& state, const VideoOutputEdgeConfig& config, const std::string& senderName);
 
 	std::string mSenderName;
 	CompletionCallback mCompletionCallback;
 	mutable std::mutex mMutex;
+	mutable std::mutex mSdkMutex;
 	void* mSender = nullptr;
 	void* mPendingBuffer = nullptr;
 	VideoOutputEdgeConfig mConfig;