Pipeline OpenCV Mat (which includes 8 bit RGB data from IP camera) to GStreamer

[Rashmi]

Hello,

Please check whether the following code is correct as I'm new to GStreamer.
I'm trying to create a pipeline from the data obtained by IP camera through
OpenCV which is present in cv::Mat (Mat includes 8bit RGB data of the
camera) and stream it through udp by encoding it using VP8. 
Please provide inputs with explanations so that I can understand as I'm
learning GStreamer.


//destroy the cv::Mat buffer 
void buffer_destroy(gpointer data) { 
  cv::Mat* done = (cv::Mat*)data; 
  delete done; 
} 

//create pipeline from cv::Mat
int createGStreamerPipeline ( cv::Mat *frame )
{
        GstElement *pipeline, *source, *filter, *encode, *pay, *udp;
	GstAppSrc *appsrc;
	GstCaps *filtercaps;
	GstBus *bus;
	GstMessage *msg;
	GMainLoop *loop;
	GstStateChangeReturn ret;
	static GstClockTime timestamp = 0;
	GstBuffer *buffer;
	int buffer_size;
	GstFlowReturn flowRet;

	//initialize all elements
//	gst_init (&argc, &argv);
	pipeline = gst_pipeline_new ("pipeline");
//	source = gst_element_factory_make ("v4l2src", "source");
        source = gst_element_factory_make ( "appsrc", "source" );
	filter = gst_element_factory_make ("capsfilter", "filter");
	encode = gst_element_factory_make ("vp8enc", "encode");
	pay = gst_element_factory_make ("rtpvp8pay", "pay");
	udp = gst_element_factory_make ("udpsink", "udp");

	//creating source
	/*buffer = gst_buffer_new_and_alloc ( ( gsize ) frame.size( ) );
	GST_BUFFER_TIMESTAMP (buffer) = timestamp;
	GST_BUFFER_DURATION (buffer) = gst_util_uint64_scale_int (frame.size( ),
GST_SECOND, 2);
	timestamp += GST_BUFFER_DURATION (buffer);
        g_signal_emit_by_name (frame.data->appsrc, "push-buffer", buffer,
&flowRet);
	gst_buffer_unref ( buffer );
	frame.data->appsrc = source; */
	
	buffer_size = frame->cols * frame->rows * frame->channels( );
	buffer = gst_buffer_new_wrapped_full( (GstMemoryFlags)0,
(gpointer)(frame->data), buffer_size, 0, buffer_size, frame, buffer_destroy
); 
	gst_app_src_push_buffer ( GST_APP_SRC ( appsrc ), buffer); 

	//check for null objects
	if (!pipeline || !source || !filter || !encode || !pay || !udp) {
		std::cout << "Failed to create all elements :" << std::endl;
		std::cout << " pipeline : " << !pipeline << std::endl;
		std::cout << "source : " << !source << std::endl;
		std::cout << "filter : " << !filter << std::endl;
		std::cout << "encode : " << !encode << std::endl;
		std::cout << "pay : " << !pay << std::endl;
		std::cout << "udp : " << !udp << std::endl;
		return -1;
	}

	//set video source
//	g_object_set (G_OBJECT (source), "device", "/dev/video1", NULL);
	std::cout << "==>set video source." << std::endl;
	g_object_set (G_OBJECT (udp), "host", "10.0.0.6", NULL);
	g_object_set (G_OBJECT (udp), "port", 5004, NULL);
	std::cout << "==>set video sink." << std::endl;
	filtercaps = gst_caps_new_simple ("video/x-raw",
			"format", G_TYPE_STRING, "RGB",
			"width", G_TYPE_INT, 640,
			"height", G_TYPE_INT, 480,
			"pixel-aspect-ratio", GST_TYPE_FRACTION, 1, 1,
			"framerate", GST_TYPE_FRACTION, 30, 1,
			NULL);
	g_object_set (G_OBJECT (filter), "caps", filtercaps, NULL);
	gst_caps_unref (filtercaps);

	//add all elements together
	gst_bin_add_many (GST_BIN (pipeline), source, filter, encode, pay, udp,
NULL);
	if (gst_element_link_many (source, filter, encode, pay, udp, NULL) != TRUE
) {
		std::cout << "Elements could not be linked." << std::endl;
	 	gst_object_unref (pipeline);
	 	return -1;
	}

	//set the pipeline state to playing
	ret = gst_element_set_state (pipeline, GST_STATE_PLAYING);
	if (ret == GST_STATE_CHANGE_FAILURE) {
		std::cout << "Unable to set the pipeline to the playing state." <<
std::endl;
		gst_object_unref (pipeline);
		return -1;
	}
	std::cout << "==>set video to play." << std::endl;

	//get pipeline's bus
	bus = gst_element_get_bus (pipeline);
	std::cout << "==>setup bus." << std::endl;

	loop = g_main_loop_new (NULL, FALSE);
	std::cout << "==>begin stream." << std::endl;
	g_main_loop_run (loop);

	g_main_loop_unref (loop);
	gst_object_unref (bus);
	gst_element_set_state (pipeline, GST_STATE_NULL);
	gst_object_unref (pipeline);

} 



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