Fix obscure effect pixelated size

data/effects/obscure.xml

@@ -3,7 +3,7 @@
 	<name>Obscure</name>
 	<description>Hide a region of the clip</description>
 	<author>Charles Yates</author>
-	<parameter type="geometry" name="start" default="40%,40%:20%x20%" fixed="1">
+	<parameter type="geometry" name="start" default="40% 40% 20% 20%" fixed="1" opacity="false">
 		<name>Region</name>
 	</parameter>
 </effect>