camerabin: add video-source-filter property

Add video-source-filter property that can be used to inject application
specific gstreamer element to camerabin pipeline. The video-source-filter
element will process all frames coming from video source.

One could add image analyzers to collect information about the stream,
or add image enhancers to improve capture quality, for example.

gst/camerabin/gstcamerabin-enum.h

@@ -55,7 +55,8 @@ enum
   ARG_EV_COMP,
   ARG_ISO_SPEED,
   ARG_APERTURE,
-  ARG_EXPOSURE
+  ARG_EXPOSURE,
+  ARG_VIDEO_SOURCE_FILTER
 };
 
 /**

gst/camerabin/gstcamerabin.c

@@ -125,7 +125,7 @@
  * The pipeline in the camerabin is
  *
  * videosrc [ ! ffmpegcsp ] ! capsfilter ! crop ! scale ! capsfilter ! \
- *     out-sel name=osel ! queue name=img_q
+ *     [ video_filter ! ] out-sel name=osel ! queue name=img_q
  *
  * View finder:
  * osel. ! in-sel name=isel ! scale ! capsfilter [ ! ffmpegcsp ] ! vfsink
@@ -583,6 +583,11 @@ camerabin_create_src_elements (GstCameraBin * camera)
             gst_camerabin_create_and_add_element (cbin, "capsfilter")))
       goto done;
   }
+  if (camera->app_video_filter) {
+    if (!gst_camerabin_add_element (cbin, camera->app_video_filter)) {
+      goto done;
+    }
+  }
   if (!(camera->src_out_sel =
           gst_camerabin_create_and_add_element (cbin, "output-selector")))
     goto done;
@@ -883,6 +888,11 @@ camerabin_dispose_elements (GstCameraBin * camera)
     camera->user_vid_src = NULL;
   }
 
+  if (camera->app_video_filter) {
+    gst_object_unref (camera->app_video_filter);
+    camera->app_video_filter = NULL;
+  }
+
   /* Free caps */
   gst_caps_replace (&camera->image_capture_caps, NULL);
   gst_caps_replace (&camera->view_finder_caps, NULL);
@@ -2580,6 +2590,23 @@ gst_camerabin_class_init (GstCameraBinClass * klass)
           "Audio source GStreamer element (NULL = default audio src)",
           GST_TYPE_ELEMENT, G_PARAM_READWRITE));
 
+  /**
+   *  GstCameraBin:video-source-filter:
+   *
+   * Set up optional video filter element, all frames from video source
+   * will be processed by this element. e.g. An application might add
+   * image enhancers/parameter adjustment filters here to improve captured
+   * image/video results, or add analyzers to give feedback on capture
+   * the application.
+   * This property can only be set while #GstCameraBin is in NULL state.
+   * The ownership of the element will be taken by #GstCameraBin.
+   */
+
+  g_object_class_install_property (gobject_class, ARG_VIDEO_SOURCE_FILTER,
+      g_param_spec_object ("video-source-filter", "video source filter element",
+          "Optional video filter GStreamer element, filters all frames from"
+          "the video source", GST_TYPE_ELEMENT, G_PARAM_READWRITE));
+
   /**
    * GstCameraBin:video-source-caps:
    *
@@ -2825,6 +2852,7 @@ gst_camerabin_init (GstCameraBin * camera, GstCameraBinClass * gclass)
   camera->src_zoom_filter = NULL;
   camera->src_out_sel = NULL;
 
+  camera->app_video_filter = NULL;
   camera->user_vid_src = NULL;
 
   camera->active_bin = NULL;
@@ -3007,6 +3035,17 @@ gst_camerabin_set_property (GObject * object, guint prop_id,
       gst_camerabin_video_set_audio_src (GST_CAMERABIN_VIDEO (camera->vidbin),
           g_value_get_object (value));
       break;
+    case ARG_VIDEO_SOURCE_FILTER:
+      if (GST_STATE (camera) != GST_STATE_NULL) {
+        GST_ELEMENT_ERROR (camera, CORE, FAILED,
+            ("camerabin must be in NULL state when setting the video filter element"),
+            (NULL));
+      } else {
+        if (camera->app_video_filter)
+          gst_object_unref (camera->app_video_filter);
+        camera->app_video_filter = g_value_dup_object (value);
+      }
+      break;
     case ARG_FILTER_CAPS:
       GST_OBJECT_LOCK (camera);
       gst_caps_replace (&camera->view_finder_caps,
@@ -3125,6 +3164,9 @@ gst_camerabin_get_property (GObject * object, guint prop_id,
           gst_camerabin_video_get_audio_src (GST_CAMERABIN_VIDEO
               (camera->vidbin)));
       break;
+    case ARG_VIDEO_SOURCE_FILTER:
+      g_value_set_object (value, camera->app_video_filter);
+      break;
     case ARG_INPUT_CAPS:
       gst_value_set_caps (value, gst_camerabin_get_allowed_input_caps (camera));
       break;

gst/camerabin/gstcamerabin.h

@@ -137,6 +137,7 @@ struct _GstCameraBin
   /* User configurable elements */
   GstElement *user_vid_src;
   GstElement *user_vf_sink;
+  GstElement *app_video_filter;
 
   /* Night mode handling */
   gboolean night_mode;