[aravis] gst: add a property for access to the underlying ArvCamera object.

[Emmanuel Pacaud <emmanuel src gnome org>]

commit 9d4bc8fdee8ce2ddcac85fbb72d5a9a075487cba
Author: Edgar Thier <edgarthier gmail com>
Date:   Wed Sep 4 17:32:58 2013 +0200

    gst: add a property for access to the underlying ArvCamera object.
    
    It allows to manipulate device parameters during runtime (like gain or
    exposure).

 gst/gstaravis.c |   58 +++++++++++++++++++++++++++++++++++++++++++++++-------
 1 files changed, 50 insertions(+), 8 deletions(-)
---
diff --git a/gst/gstaravis.c b/gst/gstaravis.c
index 6c16de9..344732f 100644
--- a/gst/gstaravis.c
+++ b/gst/gstaravis.c
@@ -48,6 +48,7 @@ enum
 {
   PROP_0,
   PROP_CAMERA_NAME,
+  PROP_CAMERA,
   PROP_GAIN,
   PROP_GAIN_AUTO,
   PROP_EXPOSURE,
@@ -266,6 +267,28 @@ gst_aravis_set_caps (GstBaseSrc *src, GstCaps *caps)
        return TRUE;
 }
 
+void
+gst_aravis_init_camera (GstAravis *gst_aravis)
+{
+       if (gst_aravis->camera != NULL)
+               g_object_unref (gst_aravis->camera);
+
+       gst_aravis->camera = arv_camera_new (gst_aravis->camera_name);
+
+       gst_aravis->gain = arv_camera_get_gain(gst_aravis->camera);
+       gst_aravis->gain_auto = arv_camera_is_gain_available(gst_aravis->camera);
+
+       gst_aravis->exposure_time_us = arv_camera_get_exposure_time(gst_aravis->camera);
+       if (arv_camera_get_exposure_time_auto(gst_aravis->camera) == ARV_AUTO_OFF)
+               gst_aravis->exposure_auto = FALSE;
+       else
+               gst_aravis->exposure_auto = TRUE;
+
+       arv_camera_get_region (gst_aravis->camera, &gst_aravis->offset_x, &gst_aravis->offset_y, NULL, NULL);
+       arv_camera_get_binning (gst_aravis->camera, &gst_aravis->h_binning, &gst_aravis->v_binning);
+       gst_aravis->payload = 0;
+}
+
 static gboolean
 gst_aravis_start (GstBaseSrc *src)
 {
@@ -273,10 +296,9 @@ gst_aravis_start (GstBaseSrc *src)
 
        GST_LOG_OBJECT (gst_aravis, "Open camera '%s'", gst_aravis->camera_name);
 
-       if (gst_aravis->camera != NULL)
-               g_object_unref (gst_aravis->camera);
+       if (gst_aravis->camera == NULL)
+               gst_aravis_init_camera (gst_aravis);
 
-       gst_aravis->camera = arv_camera_new (gst_aravis->camera_name);
        gst_aravis->all_caps = gst_aravis_get_all_camera_caps (gst_aravis);
 
        return TRUE;
@@ -294,10 +316,6 @@ gboolean gst_aravis_stop( GstBaseSrc * src )
                gst_aravis->stream = NULL;
 
        }
-       if (gst_aravis->camera != NULL) {
-               g_object_unref (gst_aravis->camera);
-               gst_aravis->camera = NULL;
-       }
        if (gst_aravis->all_caps != NULL) {
                gst_caps_unref (gst_aravis->all_caps);
                gst_aravis->all_caps = NULL;
@@ -486,22 +504,35 @@ gst_aravis_set_property (GObject * object, guint prop_id,
        switch (prop_id) {
                case PROP_CAMERA_NAME:
                        g_free (gst_aravis->camera_name);
-                       gst_aravis->camera_name = g_strdup (g_value_get_string (value));
+                       /* check if we are currently active
+                          prevent setting camera and other values to something not representing the active 
camera */
+                       if (gst_aravis->stream == NULL) {
+                               gst_aravis->camera_name = g_strdup (g_value_get_string (value));
+                               gst_aravis_init_camera (gst_aravis);
+                       }
 
                        GST_LOG_OBJECT (gst_aravis, "Set camera name to %s", gst_aravis->camera_name);
 
                        break;
                case PROP_GAIN:
                        gst_aravis->gain = g_value_get_double (value);
+                       if (gst_aravis->camera != NULL)
+                               arv_camera_set_gain (gst_aravis->camera, gst_aravis->gain);
                        break;
                case PROP_GAIN_AUTO:
                        gst_aravis->gain_auto = g_value_get_boolean (value);
+                       if (gst_aravis->camera != NULL)
+                               arv_camera_set_gain_auto (gst_aravis->camera, gst_aravis->gain_auto);
                        break;
                case PROP_EXPOSURE:
                        gst_aravis->exposure_time_us = g_value_get_double (value);
+                       if (gst_aravis->camera != NULL)
+                               arv_camera_set_exposure_time (gst_aravis->camera, 
gst_aravis->exposure_time_us);
                        break;
                case PROP_EXPOSURE_AUTO:
                        gst_aravis->exposure_auto = g_value_get_boolean (value);
+                       if (gst_aravis->camera != NULL)
+                               arv_camera_set_exposure_time_auto (gst_aravis->camera, 
gst_aravis->exposure_auto);
                        break;
                case PROP_OFFSET_X:
                        gst_aravis->offset_x = g_value_get_int (value);
@@ -531,6 +562,9 @@ gst_aravis_get_property (GObject * object, guint prop_id, GValue * value,
                case PROP_CAMERA_NAME:
                        g_value_set_string (value, gst_aravis->camera_name);
                        break;
+               case PROP_CAMERA:
+                       g_value_set_object (value, gst_aravis->camera);
+                       break;
                case PROP_GAIN:
                        g_value_set_double (value, gst_aravis->gain);
                        break;
@@ -596,6 +630,14 @@ gst_aravis_class_init (GstAravisClass * klass)
                                      G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
        g_object_class_install_property
                (gobject_class,
+                PROP_CAMERA,
+                g_param_spec_object ("camera",
+                                     "Camera Object",
+                                     "Camera instance to retrieve additional information",
+                                             ARV_TYPE_CAMERA,
+                                     G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
+       g_object_class_install_property
+               (gobject_class,
                 PROP_GAIN,
                 g_param_spec_double ("gain",
                                   "Gain",