diff --git a/libavfilter/vf_signature.c b/libavfilter/vf_signature.c
index 7d434328b7..0b364430f6 100644
--- a/libavfilter/vf_signature.c
+++ b/libavfilter/vf_signature.c
@@ -386,6 +386,9 @@ static int xml_export(AVFilterContext *ctx, StreamContext *sc, const char* filen
     FILE* f;
     unsigned int pot3[5] = { 3*3*3*3, 3*3*3, 3*3, 3, 1 };
 
+    if (!sc->coarseend->last)
+        return AVERROR(EINVAL); // No frames ?
+
     f = avpriv_fopen_utf8(filename, "w");
     if (!f) {
         int err = AVERROR(EINVAL);
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 95e44d3736..e482690fc9 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -3234,7 +3234,8 @@ static void pat_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
                     FFSWAP(struct Program, ts->prg[nb_prg], ts->prg[prg_idx]);
                 if (prg_idx >= nb_prg)
                     nb_prg++;
-            }
+            } else 
+                nb_prg = 0;
         }
     }
     ts->nb_prg = nb_prg;