Ticket #4798: h264_0.diff

libavcodec/h264.c

@@ -3911 +3911 @@
     h->slice_type= slice_type;
 
     s->pict_type= h->slice_type; // to make a few old func happy, it's wrong though
+    if (s->pict_type == B_TYPE && s->last_picture_ptr == NULL) {
+        av_log(h->s.avctx, AV_LOG_ERROR, 
+               "B picture before any references, skipping\n");
+        return -1;
+    }
 
     pps_id= get_ue_golomb(&s->gb);
     if(pps_id>=MAX_PPS_COUNT){