diff --git a/Makefile.rules.linux b/Makefile.rules.linux
index 5be2262..784621a 100644
--- a/Makefile.rules.linux
+++ b/Makefile.rules.linux
@@ -5,7 +5,7 @@ CPP = c++
 CPPFLAGS = -std=c++11 -ggdb -Wall -Werror -O0 `pkg-config --cflags gtk+-3.0 gmodule-export-2.0` -Wl,--export-dynamic -I/usr/include -DBUILD_LINUX=1
 INCLUDES = 
 LDFLAGS = 
-LIBS = `pkg-config --libs gtk+-3.0 gmodule-export-2.0` -L/usr/lib -ljpeg
+LIBS = `pkg-config --libs gtk+-3.0 gmodule-export-2.0` -L/usr/lib -ljpeg -ltiff
 OBJECTS =
 
 
diff --git a/video.cc b/video.cc
index ba39db0..28d204f 100644
--- a/video.cc
+++ b/video.cc
@@ -471,13 +471,16 @@ void cb_video_btnstop (GtkWidget *widget, gpointer data) {
  * Access to this data must be Locked before use.
  */
 gboolean cb_thread_video (gpointer data) {
-	GtkWidget *btnstart;
-	GtkWidget *btnstop;
+	GtkWidget *btnstart = GTK_WIDGET(gtk_builder_get_object (GTK_BUILDER(_builder_), "btn-video-rec"));
+	GtkWidget *btnstop = GTK_WIDGET(gtk_builder_get_object (GTK_BUILDER(_builder_), "btn-video-stop"));
 	VideoDevThreadData *cbdata = (VideoDevThreadData*) data;
 	VideoFrame *vf = NULL;
 
-//	printf ("%s:%d %s\n", __FILE__, __LINE__, __FUNCTION__);
+	if (videodev == NULL) return false;
 
+	//
+	// after video starts, on the first frame
+	// read out all controls
 	if (cbdata != NULL) {
 		vf = &cbdata->vf;
 		if (cbdata->running == 1) {
@@ -486,11 +489,9 @@ gboolean cb_thread_video (gpointer data) {
 		}
 		if (vf->w <= 0 || vf->h <= 0 || vf->data == NULL) vf = NULL;
 	}
-	if (videodev == NULL) return false;
-
-	btnstop = GTK_WIDGET(gtk_builder_get_object (GTK_BUILDER(_builder_), "btn-video-stop"));
-	btnstart = GTK_WIDGET(gtk_builder_get_object (GTK_BUILDER(_builder_), "btn-video-rec"));
 
+	//
+	// create video drawarea if needed
 	if (video_da == NULL)
 		video_da = GTK_WIDGET(gtk_builder_get_object (GTK_BUILDER(_builder_), "video-da"));
 
@@ -499,6 +500,9 @@ gboolean cb_thread_video (gpointer data) {
 		memset (gdk_pixbuf_get_pixels(video_pixbuf), 0, 3 * gdk_pixbuf_get_height(video_pixbuf) * gdk_pixbuf_get_width(video_pixbuf));
 	}
 
+	//
+	// if cbdata not set, we have a error on the video stream
+	// stop recording. Else push framedata into the detect thread.
 	if (cbdata == NULL) {
 		printf ("%s:%d %s something went wrong CBData == NULL\n", __FILE__, __LINE__, __FUNCTION__);
 		videodev->Stop();
@@ -512,6 +516,9 @@ gboolean cb_thread_video (gpointer data) {
 		int pix_h, pix_w;
 
 		videodev->LockMutex();
+
+		//
+		// check and resize video_drawarea if needed
 		if (video_pixbuf) {
 			pix_h = gdk_pixbuf_get_height(video_pixbuf);
 			pix_w = gdk_pixbuf_get_width(video_pixbuf);
@@ -526,9 +533,13 @@ gboolean cb_thread_video (gpointer data) {
 			pix_w = vf->w;
 			pix_h = vf->h;
 		}
-		vf->ToPixbuf(video_pixbuf);
-		detect.NewFrame(vf);
+
+		vf->ToPixbuf(video_pixbuf);				// convert Frame to pixeldata
+		detect.NewFrame(vf);					// push new data to detect object
+
 		videodev->UnLockMutex();
+
+		// redraw drawarea on screen.
 	    gdk_window_invalidate_rect(gtk_widget_get_window(video_da), NULL, true);
 	}