[libcamera-devel] [PATCH 6/8] qcam: Use Sensor sequence numbers and detect frame drop

[Kieran Bingham]

The stream buffer sequence numbers might produce sequential
monotonic sequence numbers from an ISP producing a frame for every
input.

This however, doesn't capture pipeline stalls that cause us to miss or
drop frames from the sensor.

Use the SensorSequence metadata to report sequence information, and
report with qInfo if a frame drop is detected.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/qcam/main_window.cpp | 22 ++++++++++++++++++++++
 src/qcam/main_window.h   |  1 +
 2 files changed, 23 insertions(+)

diff --git a/src/qcam/main_window.cpp b/src/qcam/main_window.cpp
index dd0e51f55b70..8d1d5b275aed 100644
--- a/src/qcam/main_window.cpp
+++ b/src/qcam/main_window.cpp
@@ -12,6 +12,7 @@
 #include <string>
 
 #include <libcamera/camera_manager.h>
+#include <libcamera/control_ids.h>
 #include <libcamera/version.h>
 
 #include <QComboBox>
@@ -510,6 +511,7 @@ int MainWindow::startCapture()
 	previousFrames_ = 0;
 	framesCaptured_ = 0;
 	lastBufferTime_ = 0;
+	sequence_ = 0;
 
 	ret = camera_->start();
 	if (ret) {
@@ -719,6 +721,26 @@ void MainWindow::processCapture()
 		request = doneQueue_.dequeue();
 	}
 
+	/* Parse the request metadata for useful information */
+	for (const auto &ctrl : request->metadata()) {
+		const int id = ctrl.first;
+		const ControlValue &value = ctrl.second;
+
+		if (id == controls::SensorSequence) {
+			/* Handle basic frame drop detection and reporting. */
+			int64_t sequence = value.get<int64_t>();
+			if (sequence_ == 0)
+				sequence_ = sequence - 1;
+			unsigned int drops = sequence - sequence_ - 1;
+			if (drops)
+				qInfo() << "sequence: [" << sequence << "] *"
+					<< drops << " frame drops detected *";
+			sequence_ = sequence;
+		}
+
+		/* \todo Handle all/other metadata types here. */
+	}
+
 	/* Process buffers. */
 	if (request->buffers().count(vfStream_))
 		processViewfinder(request->buffers().at(vfStream_));
diff --git a/src/qcam/main_window.h b/src/qcam/main_window.h
index 3fbe872c0b5b..97568d6b619d 100644
--- a/src/qcam/main_window.h
+++ b/src/qcam/main_window.h
@@ -120,6 +120,7 @@ private:
 	QMutex mutex_; /* Protects freeBuffers_, doneQueue_, and freeQueue_ */
 
 	uint64_t lastBufferTime_;
+	uint64_t sequence_;
 	QElapsedTimer frameRateInterval_;
 	uint32_t previousFrames_;
 	uint32_t framesCaptured_;
-- 
2.30.2