h264: do not increase recovery frame which would lead to endless moving away of the recovery point.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h264.c

@@ -3715,7 +3715,7 @@ static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size){
             if((err = decode_slice_header(hx, h)))
                break;
 
-            if (h->sei_recovery_frame_cnt >= 0) {
+            if (h->sei_recovery_frame_cnt >= 0 && h->recovery_frame < 0) {
                 h->recovery_frame = (h->frame_num + h->sei_recovery_frame_cnt) %
                                     (1 << h->sps.log2_max_frame_num);
             }