Meego camera input

[klen]

I managed to get gstreamer to work with N9. The pipeline is using appsink
element to capture images frame by frame from the camera. I am using it
coupled with openCV. The NewFrameAdded() callback is only called for the
first frame. For performance issues i rather pool the later frame myself
with PoolFrame fucntion.

CODE:
/static gboolean InitializePipeline(int *argc, char ***argv, int width, int
height, IplImage **_frame3C) {

	GstElement *image_sink, *csp_filter, *image_filter;
	GstCaps *caps;
	
	buffer_width=width;
	buffer_hight=height;
	/*Allocate memory for the frame*/
	frame3C=cvCreateImageHeader(cvSize(buffer_width,buffer_hight),
IPL_DEPTH_8U, 3); //color image
	frame1= cvCreateImage(cvSize(buffer_width,buffer_hight), IPL_DEPTH_8U, 1);
//grey current
	frame2= cvCreateImage(cvSize(buffer_width,buffer_hight), IPL_DEPTH_8U, 1);
//grey previous
	
       /*initialize flags*/
	cold_start=true;

	/* Initialize Gstreamer */
	gst_init(argc, argv);

	/* Create elements */
	/* Camera video stream comes from a Video4Linux driver */
	camera_src = gst_element_factory_make("v4l2camsrc", "camera_src");
	g_object_set(G_OBJECT(camera_src), "driver-name", "omap3cam", NULL); //
thanks BBNS_ @ maemo irc aka Yun-Ta Tsai
	/* Colorspace filter is needed to make sure that sinks understands the
stream coming from the camera */
	csp_filter = gst_element_factory_make("ffmpegcolorspace", "csp_filter");
	/* Filter to convert stream to use format that the gdkpixbuf library can
use */
	image_filter = gst_element_factory_make("ffmpegcolorspace",
"image_filter");
	/* A dummy sink for the image stream. Goes to bitheaven AppSink*/
	image_sink = gst_element_factory_make("appsink", "image_sink");

	/* Create pipeline and attach a callback to it's message bus */
	pipeline = gst_pipeline_new("test-camera");
	bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));

	/* Check that elements are correctly initialized */
	if(!(pipeline && camera_src && csp_filter && image_sink && image_filter))
	{
		g_critical("Couldn't create pipeline elements");
		return FALSE;
	}

	/* Add elements to the pipeline. This has to be done prior to linking them
*/
	gst_bin_add_many(GST_BIN(pipeline), camera_src,
csp_filter,image_filter,image_sink,NULL);

	/* Specify what kind of video is wanted from the camera */
	char caps_str[100];

sprintf(caps_str,"video/x-raw-yuv,format=(fourcc)UYVY,width=%i,height=%i",width,height);
//video/x-raw-yuv,format=(fourcc)UYVY,width=400,height=240
	printf("CAPSE STR: %s\n",caps_str);
	caps = gst_caps_from_string(caps_str); //framerate=[1/30,30/1]

	/* Link the camera source and colorspace filter using capabilitie specified
*/
	if(!gst_element_link_filtered(camera_src, csp_filter, caps))
	{
		return FALSE;
	}

	gst_caps_unref(caps);
	caps = gst_caps_new_simple("video/x-raw-rgb",
			"width", G_TYPE_INT, width,
			"height", G_TYPE_INT, height,
			NULL);
	/* Link the image-branch of the pipeline.*/
	if(!gst_element_link_many(csp_filter,image_filter, NULL)) return FALSE;
	if(!gst_element_link_filtered(image_filter, image_sink,caps)) return FALSE;

	/*Clean up*/
	gst_caps_unref(caps);

	/* Set image sink to emit handoff-signal before throwing away  it's buffer
*/
	g_object_set (G_OBJECT (image_sink), "emit-signals", TRUE, NULL);
	g_signal_connect (image_sink, "new-buffer", G_CALLBACK (NewFrameAdded),
NULL);

	return TRUE;
}

void NewFrameAdded (GstAppSink *_appsink)
{
	if(cold_start)
	{
		//initialize appsink
		printf("\nAppsink initialized!\n");
		appsink=_appsink;
		gst_app_sink_set_drop(appsink,true);
		gst_app_sink_set_emit_signals(appsink,false); // do not want to emit
signal on new frame will rather pool frames
		gst_app_sink_set_max_buffers(appsink,1);
		cold_start=false;
		scanning_status=true;
	}
	buffer = gst_app_sink_pull_buffer(appsink);
}

IplImage * PoolFrame(void){
	//printf("pool_buffeer()\n");
	/*Block untill the appsing becomes available*/

	while(appsink==NULL);

	if(appsink!=NULL){
		UnrefGstFrame();
		unsigned char* data;

		buffer = gst_app_sink_pull_buffer(appsink);
		data=(unsigned char *) GST_BUFFER_DATA (buffer);

		if(!buffer_swap)
		{
			cvSetData(frame3C ,data,buffer_width*3);
			cvCvtColor(frame3C, frame1, CV_RGB2GRAY); //can be optimized
			currentFrame=frame1;
		}else
		{
			cvSetData(frame3C ,data,buffer_width*3);
			cvCvtColor(frame3C, frame2, CV_RGB2GRAY); //can be optimized
			currentFrame=frame2;
		}
	
	        buffer_swap=!buffer_swap;
		if(focusStatus==GST_PHOTOGRAPHY_FOCUS_STATUS_RUNNING)
		{
			PoolAutoFocusBusMessage();
		}
		return currentFrame;
	}
	return currentFrame;
}
/

Hope it will be useful
Cheers,
K

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