int ff_mp4_read_descr_len(AVIOContext *pb);
int ff_mp4_read_descr(AVFormatContext *fc, AVIOContext *pb, int *tag);
int ff_mp4_read_dec_config_descr(AVFormatContext *fc, AVStream *st, AVIOContext *pb);
int ff_mp4_read_descr_len(AVIOContext *pb);
int ff_mp4_read_descr(AVFormatContext *fc, AVIOContext *pb, int *tag);
int ff_mp4_read_dec_config_descr(AVFormatContext *fc, AVStream *st, AVIOContext *pb);