rpicam-vid: Update for camera sync algorithm

A "sync" option has been added, which may take the values "server" or
"client", turning the camera into either the server of client of a
synchronised recording.

Setting the camera into sync mode, and skipping frames while waiting
for sync, is delegated to the RPiCamEncoder class, so that all video
recording applications acquire the functionality.

Signed-off-by: David Plowman <[email protected]>
Signed-off-by: Arsen Mikovic <[email protected]>
Signed-off-by: Naushir Patuck <[email protected]>

.gitignore

@@ -1,2 +1,3 @@
 build
 *~
+.vscode/

apps/rpicam_vid.cpp

@@ -117,7 +117,6 @@ static void event_loop(RPiCamEncoder &app)
 			app.StopEncoder();
 			return;
 		}
-
 		CompletedRequestPtr &completed_request = std::get<CompletedRequestPtr>(msg.payload);
 		app.EncodeBuffer(completed_request, app.VideoStream());
 		app.ShowPreview(completed_request, app.VideoStream());

core/rpicam_encoder.hpp

@@ -29,13 +29,30 @@ class RPiCamEncoder : public RPiCamApp
 		createEncoder();
 		encoder_->SetInputDoneCallback(std::bind(&RPiCamEncoder::encodeBufferDone, this, std::placeholders::_1));
 		encoder_->SetOutputReadyCallback(encode_output_ready_callback_);
+
+		// Set up the encode function to wait for synchronisation with another camera system,
+		// when this has been requested in the options.
+		VideoOptions const *options = GetOptions();
+		libcamera::ControlList cl;
+		if (options->sync == 0)
+			cl.set(libcamera::controls::rpi::SyncMode, libcamera::controls::rpi::SyncModeOff);
+		else if (options->sync == 1)
+			cl.set(libcamera::controls::rpi::SyncMode, libcamera::controls::rpi::SyncModeServer);
+		else if (options->sync == 2)
+			cl.set(libcamera::controls::rpi::SyncMode, libcamera::controls::rpi::SyncModeClient);
+		SetControls(cl);
 	}
 	// This is callback when the encoder gives you the encoded output data.
 	void SetEncodeOutputReadyCallback(EncodeOutputReadyCallback callback) { encode_output_ready_callback_ = callback; }
 	void SetMetadataReadyCallback(MetadataReadyCallback callback) { metadata_ready_callback_ = callback; }
 	void EncodeBuffer(CompletedRequestPtr &completed_request, Stream *stream)
 	{
 		assert(encoder_);
+
+		// If sync was enabled, and the SyncWait metadata is still "true" then we must skip this frame.
+		if (GetOptions()->sync && completed_request->metadata.get(controls::rpi::SyncWait).value_or(true))
+			return;
+
 		StreamInfo info = GetStreamInfo(stream);
 		FrameBuffer *buffer = completed_request->buffers[stream];
 		BufferReadSync r(this, buffer);

core/video_options.hpp

@@ -159,6 +159,8 @@ struct VideoOptions : public Options
 			 "Add a time offset (in microseconds if no units provided) to the audio stream, relative to the video stream. "
 			 "The offset value can be either positive or negative.")
 #endif
+			 ("sync", value<std::string>(&sync_)->default_value("off"),
+			  "Whether to synchronise with another camera. Use \"off\", \"server\" or \"client\".")
 			;
 		// clang-format on
 	}
@@ -191,6 +193,7 @@ struct VideoOptions : public Options
 	uint32_t segment;
 	size_t circular;
 	uint32_t frames;
+	uint32_t sync;
 
 	virtual bool Parse(int argc, char *argv[]) override
 	{
@@ -235,6 +238,15 @@ struct VideoOptions : public Options
 			level = "4.2";
 		}
 
+		if (strcasecmp(sync_.c_str(), "off") == 0)
+			sync = 0;
+		else if (strcasecmp(sync_.c_str(), "server") == 0)
+			sync = 1;
+		else if (strcasecmp(sync_.c_str(), "client") == 0)
+			sync = 2;
+		else
+			throw std::runtime_error("incorrect sync value " + sync_);
+
 		return true;
 	}
 	virtual void Print() const override
@@ -254,6 +266,7 @@ struct VideoOptions : public Options
 		std::cerr << "    split: " << split << std::endl;
 		std::cerr << "    segment: " << segment << std::endl;
 		std::cerr << "    circular: " << circular << std::endl;
+		std::cerr << "    sync: " << sync << std::endl;
 	}
 
 private:
@@ -262,4 +275,5 @@ struct VideoOptions : public Options
 	std::string av_sync_;
 	std::string audio_bitrate_;
 #endif /* LIBAV_PRESENT */
+	std::string sync_;
 };