@@ -206,6 +206,12 @@ vorbis_header (AVFormatContext * s, int idx)

         return -1;

     priv = os->private;

+

+    if (priv->packet[pkt_type>>1])

+        return -1;

+    if (pkt_type > 1 && !priv->packet[0] || pkt_type > 3 && !priv->packet[1])

+        return -1;

+

     priv->len[pkt_type >> 1] = os->psize;

     priv->packet[pkt_type >> 1] = av_mallocz(os->psize);

     memcpy(priv->packet[pkt_type >> 1], os->buf + os->pstart, os->psize);