mov_write_ftyp_tag(pb);
if(s->oformat != NULL) { if(!strcmp("3gp", s->oformat->name)) mov_write_ftyp_tag(pb); }
static int mov_write_header(AVFormatContext *s){    ByteIOContext *pb = &s->pb;    /* write ftyp */    mov_write_ftyp_tag(pb);        put_flush_packet(pb);    return 0;}