发现这个问题是在ffmpeg4之后修复的：
原因在于libavformat文件下的ftp.c文件：
修改方法：加入在TCP控制连接时加入应答代码202：

static int ftp_features(FTPContext *s)
{static const char *feat_command        = "FEAT\r\n";static const char *enable_utf8_command = "OPTS UTF8 ON\r\n";static const int feat_codes[] = {211, 0};static const int opts_codes[] = {200,202 ,451, 0};av_freep(&s->features);if (ftp_send_command(s, feat_command, feat_codes, &s->features) != 211) {av_freep(&s->features);}if (ftp_has_feature(s, "UTF8")) {int ret = ftp_send_command(s, enable_utf8_command, opts_codes, NULL);if (ret == 200 || ret == 202)s->utf8 = 1;}return 0;
}