GStreamer Basic tutorial 5 GUI Toolkit Integration

   #include <string.h>
   
   #include <gtk/gtk.h>
   #include <gst/gst.h>
   #include <gst/video/videooverlay.h>
   
   #include <gdk/gdk.h>
   #if defined (GDK_WINDOWING_X11)
   #include <gdk/gdkx.h>
   #elif defined (GDK_WINDOWING_WIN32)
   #include <gdk/gdkwin32.h>
   #elif defined (GDK_WINDOWING_QUARTZ)
   #include <gdk/gdkquartz.h>
   #endif
   
   /* Structure to contain all our information, so we can pass it around */
   typedef struct _CustomData {
     GstElement *playbin;           /* Our one and only pipeline */
   
     GtkWidget *slider;              /* Slider widget to keep track of current position */
     GtkWidget *streams_list;        /* Text widget to display info about the streams */
     gulong slider_update_signal_id; /* Signal ID for the slider update signal */
   
     GstState state;                 /* Current state of the pipeline */
     gint64 duration;                /* Duration of the clip, in nanoseconds */
   } CustomData;
   
   /* This function is called when the GUI toolkit creates the physical window that will hold the video.
    * At this point we can retrieve its handler (which has a different meaning depending on the windowing system)
    * and pass it to GStreamer through the VideoOverlay interface. */
   static void realize_cb (GtkWidget *widget, CustomData *data) {
     GdkWindow *window = gtk_widget_get_window (widget);
     guintptr window_handle;
   
     if (!gdk_window_ensure_native (window))
       g_error ("Couldn't create native window needed for GstVideoOverlay!");
   
     /* Retrieve window handler from GDK */
   #if defined (GDK_WINDOWING_WIN32)
     window_handle = (guintptr)GDK_WINDOW_HWND (window);
   #elif defined (GDK_WINDOWING_QUARTZ)
     window_handle = gdk_quartz_window_get_nsview (window);
   #elif defined (GDK_WINDOWING_X11)
     window_handle = GDK_WINDOW_XID (window);
   #endif
     /* Pass it to playbin, which implements VideoOverlay and will forward it to the video sink */
     gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY (data->playbin), window_handle);
   }
   
   /* This function is called when the PLAY button is clicked */
   static void play_cb (GtkButton *button, CustomData *data) {
     gst_element_set_state (data->playbin, GST_STATE_PLAYING);
   }
   
   /* This function is called when the PAUSE button is clicked */
   static void pause_cb (GtkButton *button, CustomData *data) {
     gst_element_set_state (data->playbin, GST_STATE_PAUSED);
   }
   
   /* This function is called when the STOP button is clicked */
   static void stop_cb (GtkButton *button, CustomData *data) {
     gst_element_set_state (data->playbin, GST_STATE_READY);
   }
   
   /* This function is called when the main window is closed */
   static void delete_event_cb (GtkWidget *widget, GdkEvent *event, CustomData *data) {
     stop_cb (NULL, data);
     gtk_main_quit ();
   }
   
   /* This function is called everytime the video window needs to be redrawn (due to damage/exposure,
    * rescaling, etc). GStreamer takes care of this in the PAUSED and PLAYING states, otherwise,
    * we simply draw a black rectangle to avoid garbage showing up. */
   static gboolean draw_cb (GtkWidget *widget, cairo_t *cr, CustomData *data) {
     if (data->state < GST_STATE_PAUSED) {
       GtkAllocation allocation;
   
       /* Cairo is a 2D graphics library which we use here to clean the video window.
        * It is used by GStreamer for other reasons, so it will always be available to us. */
       gtk_widget_get_allocation (widget, &allocation);
       cairo_set_source_rgb (cr, 0, 0, 0);
       cairo_rectangle (cr, 0, 0, allocation.width, allocation.height);
       cairo_fill (cr);
     }
   
     return FALSE;
   }
   
   /* This function is called when the slider changes its position. We perform a seek to the
    * new position here. */
   static void slider_cb (GtkRange *range, CustomData *data) {
     gdouble value = gtk_range_get_value (GTK_RANGE (data->slider));
     gst_element_seek_simple (data->playbin, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_KEY_UNIT,
         (gint64)(value * GST_SECOND));
   }
   
   /* This creates all the GTK+ widgets that compose our application, and registers the callbacks */
   static void create_ui (CustomData *data) {
     GtkWidget *main_window;  /* The uppermost window, containing all other windows */
     GtkWidget *video_window; /* The drawing area where the video will be shown */
     GtkWidget *main_box;     /* VBox to hold main_hbox and the controls */
     GtkWidget *main_hbox;    /* HBox to hold the video_window and the stream info text widget */
     GtkWidget *controls;     /* HBox to hold the buttons and the slider */
     GtkWidget *play_button, *pause_button, *stop_button; /* Buttons */
   
     main_window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
     g_signal_connect (G_OBJECT (main_window), "delete-event", G_CALLBACK (delete_event_cb), data);
   
     video_window = gtk_drawing_area_new ();
     gtk_widget_set_double_buffered (video_window, FALSE);
     g_signal_connect (video_window, "realize", G_CALLBACK (realize_cb), data);
     g_signal_connect (video_window, "draw", G_CALLBACK (draw_cb), data);
   
     play_button = gtk_button_new_from_icon_name ("media-playback-start", GTK_ICON_SIZE_SMALL_TOOLBAR);
     g_signal_connect (G_OBJECT (play_button), "clicked", G_CALLBACK (play_cb), data);
   
     pause_button = gtk_button_new_from_icon_name ("media-playback-pause", GTK_ICON_SIZE_SMALL_TOOLBAR);
     g_signal_connect (G_OBJECT (pause_button), "clicked", G_CALLBACK (pause_cb), data);
   
     stop_button = gtk_button_new_from_icon_name ("media-playback-stop", GTK_ICON_SIZE_SMALL_TOOLBAR);
     g_signal_connect (G_OBJECT (stop_button), "clicked", G_CALLBACK (stop_cb), data);
   
     data->slider = gtk_scale_new_with_range (GTK_ORIENTATION_HORIZONTAL, 0, 100, 1);
     gtk_scale_set_draw_value (GTK_SCALE (data->slider), 0);
     data->slider_update_signal_id = g_signal_connect (G_OBJECT (data->slider), "value-changed", G_CALLBACK (slider_cb), data);
   
     data->streams_list = gtk_text_view_new ();
     gtk_text_view_set_editable (GTK_TEXT_VIEW (data->streams_list), FALSE);
   
     controls = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 0);
     gtk_box_pack_start (GTK_BOX (controls), play_button, FALSE, FALSE, 2);
     gtk_box_pack_start (GTK_BOX (controls), pause_button, FALSE, FALSE, 2);
     gtk_box_pack_start (GTK_BOX (controls), stop_button, FALSE, FALSE, 2);
     gtk_box_pack_start (GTK_BOX (controls), data->slider, TRUE, TRUE, 2);
   
     main_hbox = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 0);
     gtk_box_pack_start (GTK_BOX (main_hbox), video_window, TRUE, TRUE, 0);
     gtk_box_pack_start (GTK_BOX (main_hbox), data->streams_list, FALSE, FALSE, 2);
   
     main_box = gtk_box_new (GTK_ORIENTATION_VERTICAL, 0);
     gtk_box_pack_start (GTK_BOX (main_box), main_hbox, TRUE, TRUE, 0);
     gtk_box_pack_start (GTK_BOX (main_box), controls, FALSE, FALSE, 0);
     gtk_container_add (GTK_CONTAINER (main_window), main_box);
     gtk_window_set_default_size (GTK_WINDOW (main_window), 640, 480);
   
     gtk_widget_show_all (main_window);
   }
   
   /* This function is called periodically to refresh the GUI */
   static gboolean refresh_ui (CustomData *data) {
     gint64 current = -1;
   
     /* We do not want to update anything unless we are in the PAUSED or PLAYING states */
     if (data->state < GST_STATE_PAUSED)
       return TRUE;
   
     /* If we didn't know it yet, query the stream duration */
     if (!GST_CLOCK_TIME_IS_VALID (data->duration)) {
       if (!gst_element_query_duration (data->playbin, GST_FORMAT_TIME, &data->duration)) {
         g_printerr ("Could not query current duration.\n");
       } else {
         /* Set the range of the slider to the clip duration, in SECONDS */
         gtk_range_set_range (GTK_RANGE (data->slider), 0, (gdouble)data->duration / GST_SECOND);
       }
     }
   
     if (gst_element_query_position (data->playbin, GST_FORMAT_TIME, &current)) {
       /* Block the "value-changed" signal, so the slider_cb function is not called
        * (which would trigger a seek the user has not requested) */
       g_signal_handler_block (data->slider, data->slider_update_signal_id);
       /* Set the position of the slider to the current pipeline position, in SECONDS */
       gtk_range_set_value (GTK_RANGE (data->slider), (gdouble)current / GST_SECOND);
       /* Re-enable the signal */
       g_signal_handler_unblock (data->slider, data->slider_update_signal_id);
     }
     return TRUE;
   }
   
   /* This function is called when new metadata is discovered in the stream */
   static void tags_cb (GstElement *playbin, gint stream, CustomData *data) {
     /* We are possibly in a GStreamer working thread, so we notify the main
      * thread of this event through a message in the bus */
     gst_element_post_message (playbin,
       gst_message_new_application (GST_OBJECT (playbin),
         gst_structure_new_empty ("tags-changed")));
   }
   
   /* This function is called when an error message is posted on the bus */
   static void error_cb (GstBus *bus, GstMessage *msg, CustomData *data) {
     GError *err;
     gchar *debug_info;
   
     /* Print error details on the screen */
     gst_message_parse_error (msg, &err, &debug_info);
     g_printerr ("Error received from element %s: %s\n", GST_OBJECT_NAME (msg->src), err->message);
     g_printerr ("Debugging information: %s\n", debug_info ? debug_info : "none");
     g_clear_error (&err);
     g_free (debug_info);
   
     /* Set the pipeline to READY (which stops playback) */
     gst_element_set_state (data->playbin, GST_STATE_READY);
   }
   
   /* This function is called when an End-Of-Stream message is posted on the bus.
    * We just set the pipeline to READY (which stops playback) */
   static void eos_cb (GstBus *bus, GstMessage *msg, CustomData *data) {
     g_print ("End-Of-Stream reached.\n");
     gst_element_set_state (data->playbin, GST_STATE_READY);
   }
   
   /* This function is called when the pipeline changes states. We use it to
    * keep track of the current state. */
   static void state_changed_cb (GstBus *bus, GstMessage *msg, CustomData *data) {
     GstState old_state, new_state, pending_state;
     gst_message_parse_state_changed (msg, &old_state, &new_state, &pending_state);
     if (GST_MESSAGE_SRC (msg) == GST_OBJECT (data->playbin)) {
       data->state = new_state;
       g_print ("State set to %s\n", gst_element_state_get_name (new_state));
       if (old_state == GST_STATE_READY && new_state == GST_STATE_PAUSED) {
         /* For extra responsiveness, we refresh the GUI as soon as we reach the PAUSED state */
         refresh_ui (data);
       }
     }
   }
   
   /* Extract metadata from all the streams and write it to the text widget in the GUI */
   static void analyze_streams (CustomData *data) {
     gint i;
     GstTagList *tags;
     gchar *str, *total_str;
     guint rate;
     gint n_video, n_audio, n_text;
     GtkTextBuffer *text;
   
     /* Clean current contents of the widget */
     text = gtk_text_view_get_buffer (GTK_TEXT_VIEW (data->streams_list));
     gtk_text_buffer_set_text (text, "", -1);
   
     /* Read some properties */
     g_object_get (data->playbin, "n-video", &n_video, NULL);
     g_object_get (data->playbin, "n-audio", &n_audio, NULL);
     g_object_get (data->playbin, "n-text", &n_text, NULL);
   
     for (i = 0; i < n_video; i++) {
       tags = NULL;
       /* Retrieve the stream's video tags */
       g_signal_emit_by_name (data->playbin, "get-video-tags", i, &tags);
       if (tags) {
         total_str = g_strdup_printf ("video stream %d:\n", i);
         gtk_text_buffer_insert_at_cursor (text, total_str, -1);
         g_free (total_str);
         gst_tag_list_get_string (tags, GST_TAG_VIDEO_CODEC, &str);
         total_str = g_strdup_printf ("  codec: %s\n", str ? str : "unknown");
         gtk_text_buffer_insert_at_cursor (text, total_str, -1);
         g_free (total_str);
         g_free (str);
         gst_tag_list_free (tags);
       }
     }
   
     for (i = 0; i < n_audio; i++) {
       tags = NULL;
       /* Retrieve the stream's audio tags */
       g_signal_emit_by_name (data->playbin, "get-audio-tags", i, &tags);
       if (tags) {
         total_str = g_strdup_printf ("\naudio stream %d:\n", i);
         gtk_text_buffer_insert_at_cursor (text, total_str, -1);
         g_free (total_str);
         if (gst_tag_list_get_string (tags, GST_TAG_AUDIO_CODEC, &str)) {
           total_str = g_strdup_printf ("  codec: %s\n", str);
           gtk_text_buffer_insert_at_cursor (text, total_str, -1);
           g_free (total_str);
           g_free (str);
         }
         if (gst_tag_list_get_string (tags, GST_TAG_LANGUAGE_CODE, &str)) {
           total_str = g_strdup_printf ("  language: %s\n", str);
           gtk_text_buffer_insert_at_cursor (text, total_str, -1);
           g_free (total_str);
           g_free (str);
         }
         if (gst_tag_list_get_uint (tags, GST_TAG_BITRATE, &rate)) {
           total_str = g_strdup_printf ("  bitrate: %d\n", rate);
           gtk_text_buffer_insert_at_cursor (text, total_str, -1);
           g_free (total_str);
         }
         gst_tag_list_free (tags);
       }
     }
   
     for (i = 0; i < n_text; i++) {
       tags = NULL;
       /* Retrieve the stream's subtitle tags */
       g_signal_emit_by_name (data->playbin, "get-text-tags", i, &tags);
       if (tags) {
         total_str = g_strdup_printf ("\nsubtitle stream %d:\n", i);
         gtk_text_buffer_insert_at_cursor (text, total_str, -1);
         g_free (total_str);
         if (gst_tag_list_get_string (tags, GST_TAG_LANGUAGE_CODE, &str)) {
           total_str = g_strdup_printf ("  language: %s\n", str);
           gtk_text_buffer_insert_at_cursor (text, total_str, -1);
           g_free (total_str);
           g_free (str);
         }
         gst_tag_list_free (tags);
       }
     }
   }
   
   /* This function is called when an "application" message is posted on the bus.
    * Here we retrieve the message posted by the tags_cb callback */
   static void application_cb (GstBus *bus, GstMessage *msg, CustomData *data) {
     if (g_strcmp0 (gst_structure_get_name (gst_message_get_structure (msg)), "tags-changed") == 0) {
       /* If the message is the "tags-changed" (only one we are currently issuing), update
        * the stream info GUI */
       analyze_streams (data);
     }
   }
   
   int main(int argc, char *argv[]) {
     CustomData data;
     GstStateChangeReturn ret;
     GstBus *bus;
   
     /* Initialize GTK */
     gtk_init (&argc, &argv);
   
     /* Initialize GStreamer */
     gst_init (&argc, &argv);
   
     /* Initialize our data structure */
     memset (&data, 0, sizeof (data));
     data.duration = GST_CLOCK_TIME_NONE;
   
     /* Create the elements */
     data.playbin = gst_element_factory_make ("playbin", "playbin");
   
     if (!data.playbin) {
       g_printerr ("Not all elements could be created.\n");
       return -1;
     }
   
     /* Set the URI to play */
     g_object_set (data.playbin, "uri", "https://www.freedesktop.org/software/gstreamer-sdk/data/media/sintel_trailer-480p.webm", NULL);
   
     /* Connect to interesting signals in playbin */
     g_signal_connect (G_OBJECT (data.playbin), "video-tags-changed", (GCallback) tags_cb, &data);
     g_signal_connect (G_OBJECT (data.playbin), "audio-tags-changed", (GCallback) tags_cb, &data);
     g_signal_connect (G_OBJECT (data.playbin), "text-tags-changed", (GCallback) tags_cb, &data);
   
     /* Create the GUI */
     create_ui (&data);
   
     /* Instruct the bus to emit signals for each received message, and connect to the interesting signals */
     bus = gst_element_get_bus (data.playbin);
     gst_bus_add_signal_watch (bus);
     g_signal_connect (G_OBJECT (bus), "message::error", (GCallback)error_cb, &data);
     g_signal_connect (G_OBJECT (bus), "message::eos", (GCallback)eos_cb, &data);
     g_signal_connect (G_OBJECT (bus), "message::state-changed", (GCallback)state_changed_cb, &data);
     g_signal_connect (G_OBJECT (bus), "message::application", (GCallback)application_cb, &data);
     gst_object_unref (bus);
   
     /* Start playing */
     ret = gst_element_set_state (data.playbin, GST_STATE_PLAYING);
     if (ret == GST_STATE_CHANGE_FAILURE) {
       g_printerr ("Unable to set the pipeline to the playing state.\n");
       gst_object_unref (data.playbin);
       return -1;
     }
   
     /* Register a function that GLib will call every second */
     g_timeout_add_seconds (1, (GSourceFunc)refresh_ui, &data);
   
     /* Start the GTK main loop. We will not regain control until gtk_main_quit is called. */
     gtk_main ();
   
     /* Free resources */
     gst_element_set_state (data.playbin, GST_STATE_NULL);
     gst_object_unref (data.playbin);
     return 0;
   }

   #include <gdk/gdk.h>
   #if defined (GDK_WINDOWING_X11)
   #include <gdk/gdkx.h>
   #elif defined (GDK_WINDOWING_WIN32)
   #include <gdk/gdkwin32.h>
   #elif defined (GDK_WINDOWING_QUARTZ)
   #include <gdk/gdkquartzwindow.h>
   #endif

   int main(int argc, char *argv[]) {
     CustomData data;
     GstStateChangeReturn ret;
     GstBus *bus;
   
     /* Initialize GTK */
     gtk_init (&argc, &argv);
   
     /* Initialize GStreamer */
     gst_init (&argc, &argv);
   
     /* Initialize our data structure */
     memset (&data, 0, sizeof (data));
     data.duration = GST_CLOCK_TIME_NONE;
   
     /* Create the elements */
     data.playbin = gst_element_factory_make ("playbin", "playbin");
   
     if (!data.playbin) {
       g_printerr ("Not all elements could be created.\n");
       return -1;
     }
   
     /* Set the URI to play */
     g_object_set (data.playbin, "uri", "https://www.freedesktop.org/software/gstreamer-sdk/data/media/sintel_trailer-480p.webm", NULL);