basecamerasrc: optimize state changing speed

Create preview pipeline already in initialization phase. This speeds
up NULL_TO_READY state change. Also implement a separate function for
setting the preview filter element.

This also restricts the preview filter property to work only on
NULL state.

gst-libs/gst/basecamerabinsrc/gstbasecamerasrc.c

@@ -350,7 +350,11 @@ gst_base_camera_src_set_property (GObject * object,
       if (self->preview_filter)
         gst_object_unref (self->preview_filter);
       self->preview_filter = g_value_dup_object (value);
-      self->preview_filter_changed = TRUE;
+      if (!gst_camerabin_preview_set_filter (self->preview_pipeline,
+              self->preview_filter)) {
+        GST_WARNING_OBJECT (self,
+            "Cannot change preview filter, is element in NULL state?");
+      }
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (self, prop_id, pspec);
@@ -434,23 +438,11 @@ gst_base_camera_src_change_state (GstElement * element,
       if (!construct_pipeline (self))
         return GST_STATE_CHANGE_FAILURE;
 
-      /* recreate the preview pipeline */
-      if (self->preview_pipeline && self->preview_filter_changed) {
-        gst_camerabin_destroy_preview_pipeline (self->preview_pipeline);
-        self->preview_pipeline = NULL;
-      }
-
-      if (self->preview_pipeline == NULL)
-        self->preview_pipeline =
-            gst_camerabin_create_preview_pipeline (GST_ELEMENT_CAST (self),
-            self->preview_filter);
-
       if (self->preview_pipeline == NULL) {
         /* failed to create preview pipeline, fail state change */
         return GST_STATE_CHANGE_FAILURE;
       }
 
-      self->preview_filter_changed = FALSE;
       if (self->preview_caps) {
         GST_DEBUG_OBJECT (self,
             "Setting preview pipeline caps %" GST_PTR_FORMAT,
@@ -610,6 +602,9 @@ gst_base_camera_src_init (GstBaseCameraSrc * self,
   self->capturing_mutex = g_mutex_new ();
 
   self->post_preview = DEFAULT_POST_PREVIEW;
+
+  self->preview_pipeline =
+      gst_camerabin_create_preview_pipeline (GST_ELEMENT_CAST (self), NULL);
 }
 
 void

gst-libs/gst/basecamerabinsrc/gstbasecamerasrc.h

@@ -77,7 +77,6 @@ struct _GstBaseCameraSrc
   gboolean post_preview;
   GstElement *preview_filter;
   GstCameraBinPreviewPipelineData *preview_pipeline;
-  gboolean preview_filter_changed;
 
   /* Resolution of the buffers configured to camerabin */
   gint width;

gst-libs/gst/basecamerabinsrc/gstcamerabinpreview.c

@@ -31,6 +31,9 @@
 #include "gstcamerabinpreview.h"
 #include "gstbasecamerasrc.h"
 
+GST_DEBUG_CATEGORY_EXTERN (base_camera_src_debug);
+#define GST_CAT_DEFAULT base_camera_src_debug
+
 static void _gst_camerabin_preview_set_caps (GstCameraBinPreviewPipelineData *
     preview, GstCaps * caps);
 
@@ -190,6 +193,7 @@ gst_camerabin_create_preview_pipeline (GstElement * element,
 
   data->element = element;
   data->filter = filter;
+  data->vscale = vscale;
 
   data->processing_lock = g_mutex_new ();
   data->processing_cond = g_cond_new ();
@@ -327,3 +331,74 @@ gst_camerabin_preview_set_caps (GstCameraBinPreviewPipelineData * preview,
   }
   g_mutex_unlock (preview->processing_lock);
 }
+
+/**
+ * gst_camerabin_preview_set_filter:
+ * @preview: the #GstCameraBinPreviewPipelineData
+ * @filter: Custom filter to process preview data (an extra ref is taken)
+ *
+ * Set the filter element into preview pipeline.
+ *
+ * Returns: %TRUE on success
+ */
+gboolean
+gst_camerabin_preview_set_filter (GstCameraBinPreviewPipelineData * preview,
+    GstElement * filter)
+{
+  gboolean ret = TRUE;
+  GstState current;
+
+  g_return_val_if_fail (preview != NULL, FALSE);
+
+  GST_DEBUG ("Preview pipeline setting new filter %p", filter);
+
+  g_mutex_lock (preview->processing_lock);
+
+  gst_element_get_state (preview->pipeline, &current, NULL, 0);
+
+  if (preview->processing == 0 && current == GST_STATE_NULL) {
+    gboolean linkfail = FALSE;
+
+    if (preview->filter) {
+      /* Unlink and remove old filter */
+      gst_element_unlink (preview->appsrc, preview->filter);
+      gst_element_unlink (preview->filter, preview->vscale);
+      gst_bin_remove (GST_BIN (preview->pipeline), preview->filter);
+    } else {
+      /* Make room for filter by breaking the link between appsrc and vcale */
+      gst_element_unlink (preview->appsrc, preview->vscale);
+    }
+
+    if (filter) {
+      /* Add and link the new filter between appsrc and vscale */
+      gst_bin_add (GST_BIN (preview->pipeline), gst_object_ref (filter));
+
+      linkfail |=
+          GST_PAD_LINK_FAILED (gst_element_link_pads_full (preview->appsrc,
+              "src", filter, NULL, GST_PAD_LINK_CHECK_NOTHING));
+
+      linkfail |=
+          GST_PAD_LINK_FAILED (gst_element_link_pads_full (filter, NULL,
+              preview->vscale, "sink", GST_PAD_LINK_CHECK_CAPS));
+    } else {
+      /* No filter was given. Just link the appsrc to vscale directly */
+      linkfail |=
+          GST_PAD_LINK_FAILED (gst_element_link_pads_full (preview->appsrc,
+              "src", preview->vscale, "sink", GST_PAD_LINK_CHECK_NOTHING));
+    }
+
+    if (linkfail) {
+      GST_WARNING ("Linking the filter to pipeline failed");
+      ret = FALSE;
+    } else {
+      GST_DEBUG ("Linking the filter to pipeline successful");
+      preview->filter = filter;
+    }
+  } else {
+    GST_WARNING ("Cannot change filter when pipeline is running");
+    ret = FALSE;
+  }
+  g_mutex_unlock (preview->processing_lock);
+
+  return ret;
+}

gst-libs/gst/basecamerabinsrc/gstcamerabinpreview.h

@@ -36,6 +36,7 @@ typedef struct
   GstElement *appsrc;
   GstElement *filter;
   GstElement *appsink;
+  GstElement *vscale;
 
   GstElement *element;
 
@@ -50,5 +51,6 @@ GstCameraBinPreviewPipelineData *gst_camerabin_create_preview_pipeline (GstEleme
 void gst_camerabin_destroy_preview_pipeline (GstCameraBinPreviewPipelineData * preview);
 gboolean gst_camerabin_preview_pipeline_post (GstCameraBinPreviewPipelineData * preview, GstBuffer * buffer);
 void gst_camerabin_preview_set_caps (GstCameraBinPreviewPipelineData * preview, GstCaps * caps);
+gboolean gst_camerabin_preview_set_filter (GstCameraBinPreviewPipelineData * preview, GstElement * filter);
 
 #endif /* #ifndef __CAMERABIN_PREVIEW_H_ */