+ DCPOMATIC_ASSERT (film);
+
+ DCPTime len (s.length (), film->active_frame_rate_change (position ()));
+
+ /* Default to turning these subtitles on */
+ set_use_subtitles (true);
+
+ boost::mutex::scoped_lock lm (_mutex);
+ _length = len;
+ add_font (shared_ptr<Font> (new Font (font_id)));