-extern AVOutputFormat ff_mpeg1vcd_muxer;
-extern AVOutputFormat ff_mpeg2dvd_muxer;
-extern AVOutputFormat ff_mpeg2svcd_muxer;
-extern AVOutputFormat ff_mpeg2vob_muxer;
+extern const AVOutputFormat ff_mpeg1vcd_muxer;
+extern const AVOutputFormat ff_mpeg2dvd_muxer;
+extern const AVOutputFormat ff_mpeg2svcd_muxer;
+extern const AVOutputFormat ff_mpeg2vob_muxer;