if(!strcmp("3gp", s->oformat->name)) mov_write_ftyp_tag(pb);
if(!strcmp("3gp", s->oformat->name) || !strcmp("mp4", s->oformat->name)) mov_write_ftyp_tag(pb,s);
static int mov_write_header(AVFormatContext *s){    ByteIOContext *pb = &s->pb;    if(s->oformat != NULL) {    if(!strcmp("3gp", s->oformat->name))        mov_write_ftyp_tag(pb);    }    put_flush_packet(pb);    return 0;}