+int ff_mp4_read_descr(AVFormatContext *fc, ByteIOContext *pb, int *tag);
+int ff_mp4_read_dec_config_descr(AVFormatContext *fc, AVStream *st, ByteIOContext *pb);
+
+#define MP4IODescrTag 0x02
+#define MP4ESDescrTag 0x03
+#define MP4DecConfigDescrTag 0x04
+#define MP4DecSpecificDescrTag 0x05
+