Hello all, I still have some questions about gstreamer. Actually I'd like to change the way my program work, in order to display a frame from the camera only once the image processing has been done, and with a rectangle over the face of the person. So I changed my pipeline (removed the screen_sink element), and I'd like to send a buffer from my image processing function to the gtk drawing area where the camera image was displayed before. I tried to do it with gtk drawing area (and with gtk image too with no sucess), but I can't find the way to change the image contained in the drawing area. Here is my code : ///// IMAGE PROCESSING CALLBACK /* Callback to be called when data goes through the pad */ static gboolean process_frame(GstElement *video_sink,         GstBuffer *buffer, GstPad *pad, AppData *appdata) {         int x, y;         // getting the pointer to camera buffer         unsigned char *data_photo = (unsigned char *) GST_BUFFER_DATA(buffer);         // REMOVED PART WHERE THE COORDINATES OF THE POSITION OF THE FACE IS CALCULATED //         // THIS PART IS WHAT I TRIED, BUT I HAVE A SEGMENTATION FAULT WHEN CREATING PIXBUF //               GdkPixbuf *newscreen;         //newscreen = gdk_pixbuf_new_from_data(data_photo,                     //GDK_COLORSPACE_RGB, /* RGB-colorspace */                     //FALSE, /* No alpha-channel */                     //8, /* Bits per RGB-component */                     //IMAGE_WIDTH, IMAGE_HEIGHT, /* Dimensions */                     //3*IMAGE_WIDTH, /* Number of bytes between lines (ie stride) */                     //NULL, NULL); /* Callbacks */ gdk_draw_pixmap(GDK_DRAWABLE(appdata->screen), appdata->screen->style->black_gc, GDK_DRAWABLE(newscreen), 0, 0, 0, 0, -1, -1);                        return TRUE; } /////// PIPELINE /* Initialize the the Gstreamer pipeline. Below is a diagram  * of the pipeline that will be created:  *                           * |Camera|  |CSP   |  |Screen|  |Screen|   |Image     |  * |src   |->|Filter|->|queue |->|sink  |-> |processing|->  Display  */ static gboolean initialize_pipeline(AppData *appdata,         int *argc, char ***argv) {     GstElement *pipeline, *camera_src, *screen_sink;     GstElement *screen_queue;     GstElement *csp_filter;     GstCaps *caps;     GstBus *bus;     GstPad *sinkpad;     /* Initialize Gstreamer */     gst_init(argc, argv);         /* 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));     gst_bus_add_watch(bus, (GstBusFunc)bus_callback, appdata);     gst_object_unref(GST_OBJECT(bus));         /* Save pipeline to the AppData structure */     appdata->pipeline = pipeline;         /* Create elements */     /* Camera video stream comes from a Video4Linux driver */     camera_src = gst_element_factory_make(VIDEO_SRC, "camera_src");     /* 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");     /* Queue creates new thread for the stream */     screen_queue = gst_element_factory_make("queue", "screen_queue");     /* Sink that shows the image on screen. Xephyr doesn't support XVideo      * extension, so it needs to use ximagesink, but the device uses      * xvimagesink */     //screen_sink = gst_element_factory_make(VIDEO_SINK, "screen_sink");     sinkpad = gst_element_get_static_pad(screen_queue,"sink");     gst_pad_add_buffer_probe(sinkpad,G_CALLBACK(process_frame), appdata);     /* Check that elements are correctly initialized */     if(!(pipeline && camera_src /*&& screen_sink*/ && csp_filter && screen_queue))     {         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,             screen_queue, /*screen_sink,*/ NULL);         /* Specify what kind of video is wanted from the camera */     caps = gst_caps_new_simple("video/x-raw-rgb",             "width", G_TYPE_INT, IMAGE_WIDTH,             "height", G_TYPE_INT, IMAGE_HEIGHT,             "framerate", GST_TYPE_FRACTION, FRAMERATE, 1,             NULL);                 /* Link the camera source and colorspace filter using capabilities      * specified */     if(!gst_element_link_filtered(camera_src, csp_filter, caps))     {         return FALSE;     }     gst_caps_unref(caps);         /* Connect Colorspace Filter -> Screen Queue -> Screen Sink      * This finalizes the initialization of the screen-part of the pipeline */     if(!gst_element_link_many(csp_filter, screen_queue, /*screen_sink, */NULL))     {         return FALSE;     }     gst_element_set_state(pipeline, GST_STATE_PAUSED);        return TRUE; } /////// MAIN FUNCTION int main(int argc, char **argv) { // variables for face detection     // main structure for vjdetect     pdata = (mainstruct*) calloc(1, sizeof(mainstruct));     // Allocate memory for array of face detections returned by facedetector (VjDetect).     pdata->pFaceDetections = (FLY_Rect *)calloc(MAX_NUMBER_OF_FACE_DETECTIONS, sizeof(FLY_Rect));     init(pdata);     AppData appdata;     appdata.expression = 0;     GtkWidget *hbox, *vbox_button, *vbox, *button1, *button2;         /* Initialize and create the GUI */         example_gui_initialize(         &appdata.program, &appdata.window,         &argc, &argv, "Expression Detector");     vbox = gtk_vbox_new(FALSE, 0);     hbox = gtk_hbox_new(FALSE, 0);     vbox_button = gtk_vbox_new(FALSE, 0);     gtk_box_pack_start(GTK_BOX(hbox), vbox, FALSE, FALSE, 0);     gtk_box_pack_start(GTK_BOX(hbox), vbox_button, FALSE, FALSE, 0);     appdata.screen = gtk_drawing_area_new();     gtk_widget_set_size_request(appdata.screen, 500, 380);     gtk_box_pack_start(GTK_BOX(vbox), appdata.screen, FALSE, FALSE, 0);     button1 = gtk_toggle_button_new_with_label("Run/Stop");     gtk_widget_set_size_request(button1, 170, 75);     gtk_box_pack_start(GTK_BOX(vbox_button), button1, FALSE, FALSE, 0);     button2 = gtk_toggle_button_new_with_label("Expressions ON/OFF");     gtk_widget_set_size_request(button2, 170, 75);     gtk_box_pack_start(GTK_BOX(vbox_button), button2, FALSE, FALSE, 0);     appdata.anger = gtk_image_new_from_file("./smileys/anger.jpg");     gtk_widget_set_size_request(appdata.anger, 160, 180);     appdata.disgust = gtk_image_new_from_file("./smileys/disgust.jpg");     gtk_widget_set_size_request(appdata.disgust, 160, 180);     appdata.fear = gtk_image_new_from_file("./smileys/fear.jpg");     gtk_widget_set_size_request(appdata.fear, 160, 180);     appdata.happy = gtk_image_new_from_file("./smileys/happy.jpg");     gtk_widget_set_size_request(appdata.happy, 160, 180);     appdata.neutral = gtk_image_new_from_file("./smileys/neutral.jpg");     gtk_widget_set_size_request(appdata.neutral, 160, 180);     appdata.sad = gtk_image_new_from_file("./smileys/sad.jpg");     gtk_widget_set_size_request(appdata.sad, 160, 180);     appdata.surprise = gtk_image_new_from_file("./smileys/surprise.jpg");     gtk_widget_set_size_request(appdata.surprise, 160, 180);     appdata.unknown = gtk_image_new_from_file("./smileys/unknown.jpg");     gtk_widget_set_size_request(appdata.unknown, 160, 180);         appdata.smiley = gtk_image_new_from_file("./smileys/unknown.jpg");     gtk_widget_set_size_request(appdata.smiley, 160, 180);     gtk_box_pack_start(GTK_BOX(vbox_button), appdata.smiley, FALSE, FALSE, 0);         g_signal_connect(G_OBJECT(button1), "clicked",              G_CALLBACK(button1_pressed), &appdata);     g_signal_connect(G_OBJECT(button2), "clicked",              G_CALLBACK(button2_pressed), &appdata);     gtk_container_add(GTK_CONTAINER(appdata.window), hbox);     /* Initialize the GTK pipeline */     if(!initialize_pipeline(&appdata, &argc, &argv))     {         hildon_banner_show_information(                 GTK_WIDGET(appdata.window),                 "gtk-dialog-error",                 "Failed to initialize pipeline");     }     g_signal_connect(G_OBJECT(appdata.window), "destroy",             G_CALLBACK(destroy_pipeline), &appdata);     /* Begin the main application */     example_gui_run(appdata.program, appdata.window);     /* Free the gstreamer resources. Elements added      * to the pipeline will be freed automatically */         return 0; } What I'd like to do is to modify the data_photo buffer to draw a rectangle in it (in the process_frame function), and draw the content in the appdata.screen GtkWidget. (by the way screen is declared as a GtkWidget * in the appdata structure). Thanks in advance for your help ! Bruno