Limit framerate when streaming.

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>

diff --git a/libcheese/cheese-camera.c b/libcheese/cheese-camera.c
index 63e4139..2e3b08b 100644
--- a/libcheese/cheese-camera.c
+++ b/libcheese/cheese-camera.c
@@ -341,7 +341,7 @@ cheese_camera_create_camera_source_bin (CheeseCamera *camera)
   }
 
   camera_input = g_strdup_printf (
-    "%s name=video_source device=%s ! capsfilter name=capsfilter ! identity",
+    "%s name=video_source device=%s ! capsfilter name=capsfilter ! video/x-raw-yuv, framerate=[1/1, 30/1] ! identity",
     cheese_camera_device_get_src (selected_camera),
     cheese_camera_device_get_device_file (selected_camera));
 
