Stage 1 rewrite

apps/LoopThroughWithOpenGLCompositing/videoio/VideoBackend.cpp

@@ -513,7 +513,6 @@ void VideoBackend::ProcessOutputFrameCompletion(const VideoIOCompletion& complet
 	}
 	NotifyOutputProducer();
 
-	NotifyOutputProducer();
 	RecordBackendPlayoutHealth(completion.result, recoveryDecision);
 	RecordSystemMemoryPlayoutStats();
 }
@@ -702,10 +701,12 @@ bool VideoBackend::ScheduleReadyOutputFrame()
 
 	if (!ScheduleOutputFrame(readyFrame.frame))
 	{
+		RecordDeckLinkBufferTelemetry();
 		mSystemOutputFramePool.ReleaseSlotByBuffer(readyFrame.frame.bytes);
 		return false;
 	}
 
+	RecordDeckLinkBufferTelemetry();
 	PublishOutputFrameScheduled(readyFrame.frame);
 	RecordSystemMemoryPlayoutStats();
 	return true;
@@ -726,10 +727,12 @@ bool VideoBackend::ScheduleBlackUnderrunFrame()
 
 	if (!ScheduleOutputFrame(outputFrame))
 	{
+		RecordDeckLinkBufferTelemetry();
 		ApplyLifecycleTransition(VideoBackendLifecycleState::Degraded, "Output underrun: black fallback frame scheduling failed.");
 		return false;
 	}
 
+	RecordDeckLinkBufferTelemetry();
 	ApplyLifecycleTransition(VideoBackendLifecycleState::Degraded, "Output underrun: scheduled black fallback frame.");
 	PublishOutputFrameScheduled(outputFrame);
 	return true;
@@ -787,10 +790,25 @@ void VideoBackend::RecordReadyQueueDepthSample(const RenderOutputQueueMetrics& m
 		++mReadyQueueZeroDepthCount;
 }
 
+void VideoBackend::RecordDeckLinkBufferTelemetry()
+{
+	if (!mVideoIODevice)
+		return;
+
+	const VideoIOState& state = mVideoIODevice->State();
+	mHealthTelemetry.TryRecordDeckLinkBufferTelemetry(
+		state.actualDeckLinkBufferedFramesAvailable,
+		state.actualDeckLinkBufferedFrames,
+		static_cast<std::size_t>(mPlayoutPolicy.targetPrerollFrames),
+		state.deckLinkScheduleCallMilliseconds,
+		state.deckLinkScheduleFailureCount);
+}
+
 void VideoBackend::RecordSystemMemoryPlayoutStats()
 {
 	const SystemOutputFramePoolMetrics poolMetrics = mSystemOutputFramePool.GetMetrics();
 	const RenderOutputQueueMetrics queueMetrics = mReadyOutputQueue.GetMetrics();
+	RecordDeckLinkBufferTelemetry();
 	mHealthTelemetry.TryRecordSystemMemoryPlayoutStats(
 		poolMetrics.freeCount,
 		poolMetrics.readyCount,