@@ -3148,6 +3148,7 @@ static int decode_slice_header(H264Context *h, H264Context *h0)

     int must_reinit;

     int needs_reinit = 0;

     int first_slice = h == h0 && !h0->current_slice;

+    int frame_num;

     PPS *pps;

     h->me.qpel_put = h->h264qpel.put_h264_qpel_pixels_tab;

@@ -3333,7 +3334,15 @@ static int decode_slice_header(H264Context *h, H264Context *h0)

         init_dequant_tables(h);

     }

-    h->frame_num = get_bits(&h->gb, h->sps.log2_max_frame_num);

+    frame_num = get_bits(&h->gb, h->sps.log2_max_frame_num);

+    if (!first_slice) {

+        if (h0->frame_num != frame_num) {

+            av_log(h->avctx, AV_LOG_ERROR, "Frame num change from %d to %d\n",

+                   h0->frame_num, frame_num);

+            return AVERROR_INVALIDDATA;

+        }

+    }

+    h->frame_num = frame_num;

     h->mb_mbaff        = 0;

     h->mb_aff_frame    = 0;