camerabin: add "preview-source-filter" property

Adds 'preview-source-filter' for adding an element to proccess
the preview images before posting them to the bus.

gst/camerabin/camerabinpreview.c

@@ -68,7 +68,8 @@ create_element (const gchar * factory_name, const gchar * elem_name,
  * Returns: New pipeline, or NULL if error occured.
  */
 GstElement *
-gst_camerabin_preview_create_pipeline (GstCameraBin * camera, GstCaps * caps)
+gst_camerabin_preview_create_pipeline (GstCameraBin * camera, GstCaps * caps,
+    GstElement * src_filter)
 {
   GstElement *pipe, *src, *csp, *filter, *vscale, *sink;
   GError *error = NULL;
@@ -93,6 +94,9 @@ gst_camerabin_preview_create_pipeline (GstCameraBin * camera, GstCaps * caps)
 
   GST_DEBUG ("adding elements");
   gst_bin_add_many (GST_BIN (pipe), src, csp, filter, vscale, sink, NULL);
+  if (src_filter) {
+    gst_bin_add (GST_BIN (pipe), src_filter);
+  }
 
   GST_DEBUG ("preview format is: %" GST_PTR_FORMAT, caps);
 
@@ -105,9 +109,20 @@ gst_camerabin_preview_create_pipeline (GstCameraBin * camera, GstCaps * caps)
   if (!gst_element_link_pads (src, "src", vscale, "sink"))
     return FALSE;
 
-  GST_DEBUG ("linking vscale->csp");
+  if (src_filter) {
-  if (!gst_element_link_pads (vscale, "src", csp, "sink"))
+    GST_DEBUG ("linking vscale->filter");
-    return FALSE;
+    if (!gst_element_link_pads (vscale, "src", src_filter, "sink")) {
+      return FALSE;
+    }
+    GST_DEBUG ("linking filter->csp");
+    if (!gst_element_link_pads (src_filter, "src", csp, "sink")) {
+      return FALSE;
+    }
+  } else {
+    GST_DEBUG ("linking vscale->csp");
+    if (!gst_element_link_pads (vscale, "src", csp, "sink"))
+      return FALSE;
+  }
 
   GST_DEBUG ("linking csp->capsfilter");
   if (!gst_element_link_pads (csp, "src", filter, "sink"))

gst/camerabin/camerabinpreview.h

@@ -27,7 +27,7 @@
 
 G_BEGIN_DECLS
     GstElement * gst_camerabin_preview_create_pipeline (GstCameraBin * camera,
-    GstCaps * caps);
+    GstCaps * caps, GstElement * src_filter);
 
 void gst_camerabin_preview_destroy_pipeline (GstCameraBin * camera,
     GstElement * pipeline);

gst/camerabin/gstcamerabin-enum.h

@@ -66,7 +66,8 @@ enum
   ARG_IMAGE_CAPTURE_HEIGHT,
   ARG_VIDEO_CAPTURE_WIDTH,
   ARG_VIDEO_CAPTURE_HEIGHT,
-  ARG_VIDEO_CAPTURE_FRAMERATE
+  ARG_VIDEO_CAPTURE_FRAMERATE,
+  ARG_PREVIEW_SOURCE_FILTER
 };
 
 /**

gst/camerabin/gstcamerabin.c

@@ -890,6 +890,16 @@ camerabin_dispose_elements (GstCameraBin * camera)
     camera->app_viewfinder_filter = NULL;
   }
 
+  if (camera->app_preview_source_filter) {
+    gst_object_unref (camera->app_preview_source_filter);
+    camera->app_preview_source_filter = NULL;
+  }
+
+  if (camera->app_video_preview_source_filter) {
+    gst_object_unref (camera->app_video_preview_source_filter);
+    camera->app_video_preview_source_filter = NULL;
+  }
+
   /* Free caps */
   gst_caps_replace (&camera->image_capture_caps, NULL);
   gst_caps_replace (&camera->view_finder_caps, NULL);
@@ -2856,6 +2866,22 @@ gst_camerabin_class_init (GstCameraBinClass * klass)
           "Caps defining the preview image format",
           GST_TYPE_CAPS, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  /**
+   * GstCameraBin:preview-source-filter:
+   * Set up preview filter element, all frames coming from appsrc
+   * element will be processed by this element.
+   * Applications can use this to overlay text/images for preview frame, 
+   * for example.
+   * 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_PREVIEW_SOURCE_FILTER,
+      g_param_spec_object ("preview-source-filter",
+          "preview source filter element",
+          "Optional preview source filter GStreamer element",
+          GST_TYPE_ELEMENT, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   /**
    * GstCameraBin:viewfinder-filter:
    * Set up viewfinder filter element, all frames going to viewfinder sink
@@ -3155,6 +3181,10 @@ gst_camerabin_init (GstCameraBin * camera, GstCameraBinClass * gclass)
   camera->app_vf_sink = NULL;
   camera->app_viewfinder_filter = NULL;
 
+  /* preview elements */
+  camera->app_preview_source_filter = NULL;
+  camera->app_video_preview_source_filter = NULL;
+
   /* source elements */
   camera->src_vid_src = NULL;
   camera->src_filter = NULL;
@@ -3337,14 +3367,17 @@ gst_camerabin_set_property (GObject * object, guint prop_id,
     case ARG_PREVIEW_CAPS:
     {
       GstElement **prev_pipe = NULL;
+      GstElement **preview_source_filter = NULL;
       GstCaps **prev_caps = NULL;
       GstCaps *new_caps = NULL;
 
       if (camera->mode == MODE_IMAGE) {
         prev_pipe = &camera->preview_pipeline;
+        preview_source_filter = &camera->app_preview_source_filter;
         prev_caps = &camera->preview_caps;
       } else if (camera->mode == MODE_VIDEO) {
         prev_pipe = &camera->video_preview_pipeline;
+        preview_source_filter = &camera->app_video_preview_source_filter;
         prev_caps = &camera->video_preview_caps;
       }
 
@@ -3363,11 +3396,45 @@ gst_camerabin_set_property (GObject * object, guint prop_id,
 
         if (new_caps && !gst_caps_is_any (new_caps) &&
             !gst_caps_is_empty (new_caps)) {
-          *prev_pipe = gst_camerabin_preview_create_pipeline (camera, new_caps);
+          *prev_pipe =
+              gst_camerabin_preview_create_pipeline (camera, new_caps,
+              *preview_source_filter);
         }
       }
       break;
     }
+    case ARG_PREVIEW_SOURCE_FILTER:
+      if (GST_STATE (camera) != GST_STATE_NULL) {
+        GST_ELEMENT_ERROR (camera, CORE, FAILED,
+            ("camerabin must be in NULL state when setting the preview source filter element"),
+            (NULL));
+      } else {
+        GstElement **preview_pipe = NULL;
+        GstElement **preview_source_filter = NULL;
+        GstCaps *preview_caps = NULL;
+
+        if (camera->mode == MODE_IMAGE) {
+          preview_pipe = &camera->preview_pipeline;
+          preview_source_filter = &camera->app_preview_source_filter;
+          preview_caps = camera->preview_caps;
+        } else if (camera->mode == MODE_VIDEO) {
+          preview_pipe = &camera->video_preview_pipeline;
+          preview_source_filter = &camera->app_video_preview_source_filter;
+          preview_caps = camera->video_preview_caps;
+        }
+
+        if (*preview_source_filter)
+          gst_object_unref (*preview_source_filter);
+        *preview_source_filter = g_value_dup_object (value);
+
+        if (*preview_pipe) {
+          gst_camerabin_preview_destroy_pipeline (camera, *preview_pipe);
+          *preview_pipe =
+              gst_camerabin_preview_create_pipeline (camera, preview_caps,
+              *preview_source_filter);
+        }
+      }
+      break;
     case ARG_VIEWFINDER_FILTER:
       if (GST_STATE (camera) != GST_STATE_NULL) {
         GST_ELEMENT_ERROR (camera, CORE, FAILED,
@@ -3526,6 +3593,12 @@ gst_camerabin_get_property (GObject * object, guint prop_id,
       else if (camera->mode == MODE_VIDEO)
         gst_value_set_caps (value, camera->video_preview_caps);
       break;
+    case ARG_PREVIEW_SOURCE_FILTER:
+      if (camera->mode == MODE_IMAGE)
+        g_value_set_object (value, camera->app_preview_source_filter);
+      else if (camera->mode == MODE_VIDEO)
+        g_value_set_object (value, camera->app_video_preview_source_filter);
+      break;
     case ARG_VIEWFINDER_FILTER:
       g_value_set_object (value, camera->app_viewfinder_filter);
       break;

gst/camerabin/gstcamerabin.h

@@ -162,6 +162,8 @@ struct _GstCameraBin
   GstElement *app_vf_sink;
   GstElement *app_video_filter;
   GstElement *app_viewfinder_filter;
+  GstElement *app_preview_source_filter;
+  GstElement *app_video_preview_source_filter;
 
   /* Night mode handling */
   gboolean night_mode;