+typedef boost::function<void (NoteType, std::string)> NoteHandler;
+
+/** Maximum absolute difference between dcp::SubtitleString::aspect_adjust values that
+ * are considered equal.
+ */
+const float ASPECT_ADJUST_EPSILON = 1e-3;
+
+/** Maximum absolute difference between dcp::SubtitleString alignment values that
+ * are considered equal.
+ */
+const float ALIGN_EPSILON = 1e-3;