clapper-gtk: video: Use "scaletempo" by default

Do not require applications to import GStreamer and their devs to learn its
basics just to set this single element. Similarly as ClapperGtkVideo sets
"clappersink" during construction, it can also set "scaletempo" as this is
the most common choice for an audio filter.

Elements can still be changed like before if desired by setting corresponding
player properties.

src/bin/clapper-app/clapper-app-window.c

@@ -1220,7 +1220,6 @@ clapper_app_window_constructed (GObject *object)
   ClapperPlayer *player = clapper_app_window_get_player (self);
   ClapperQueue *queue = clapper_player_get_queue (player);
   ClapperGtkExtraMenuButton *button;
-  GstElement *element;
   AdwStyleManager *manager;
 
   static const GActionEntry win_entries[] = {
@@ -1266,9 +1265,6 @@ clapper_app_window_constructed (GObject *object)
 
   /* FIXME: Allow setting sink/filter elements from prefs window
    * (this should include parsing bin descriptions) */
-  element = gst_element_factory_make ("scaletempo", NULL);
-  if (G_LIKELY (element != NULL))
-    clapper_player_set_audio_filter (player, element);
 
   clapper_player_set_autoplay (player, TRUE);
 

src/lib/clapper-gtk/clapper-gtk-video.c

@@ -1108,6 +1108,11 @@ _fading_overlay_revealed_cb (GtkRevealer *revealer,
  *
  * Creates a new #ClapperGtkVideo instance.
  *
+ * Newly created video widget will also set some default GStreamer elements
+ * on its [class@Clapper.Player]. This includes Clapper own video sink and
+ * a "scaletempo" element as audio filter. Both can still be changed after
+ * construction by setting corresponding player properties.
+ *
  * Returns: a new video #GtkWidget.
  */
 GtkWidget *
@@ -1397,7 +1402,7 @@ static void
 clapper_gtk_video_constructed (GObject *object)
 {
   ClapperGtkVideo *self = CLAPPER_GTK_VIDEO_CAST (object);
-  GstElement *vsink = gst_element_factory_make ("clappersink", NULL);
+  GstElement *afilter, *vsink;
   ClapperQueue *queue;
 
   self->player = clapper_player_new ();
@@ -1408,6 +1413,8 @@ clapper_gtk_video_constructed (GObject *object)
   g_signal_connect (self->player, "notify::video-sink",
       G_CALLBACK (_video_sink_changed_cb), self);
 
+  vsink = gst_element_factory_make ("clappersink", NULL);
+
   /* FIXME: This is a temporary workaround for lack
    * of DMA_DRM negotiation support in sink itself */
   if (G_LIKELY (vsink != NULL)) {
@@ -1422,9 +1429,13 @@ clapper_gtk_video_constructed (GObject *object)
         vsink = bin;
       }
     }
+
+    clapper_player_set_video_sink (self->player, vsink);
   }
 
-  clapper_player_set_video_sink (self->player, vsink);
+  afilter = gst_element_factory_make ("scaletempo", NULL);
+  if (G_LIKELY (afilter != NULL))
+    clapper_player_set_audio_filter (self->player, afilter);
 
   g_signal_connect (self->player, "error",
       G_CALLBACK (_player_error_cb), self);