ffmpeg: prevent pts < dts to be passed through to the muxer on stream copy

Fixes Ticket3658
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

ffmpeg.c

@@ -636,7 +636,8 @@ static void write_frame(AVFormatContext *s, AVPacket *pkt, OutputStream *ost)
         bsfc = bsfc->next;
     }
 
-    if (!(s->oformat->flags & AVFMT_NOTIMESTAMPS) &&
+    if (!(s->oformat->flags & AVFMT_NOTIMESTAMPS)) {
+     if(
         (avctx->codec_type == AVMEDIA_TYPE_AUDIO || avctx->codec_type == AVMEDIA_TYPE_VIDEO) &&
         pkt->dts != AV_NOPTS_VALUE &&
         ost->last_mux_dts != AV_NOPTS_VALUE) {
@@ -657,6 +658,16 @@ static void write_frame(AVFormatContext *s, AVPacket *pkt, OutputStream *ost)
             pkt->pts = FFMAX(pkt->pts, max);
         pkt->dts = max;
       }
+     }
+        if (pkt->dts != AV_NOPTS_VALUE &&
+            pkt->pts != AV_NOPTS_VALUE &&
+            pkt->dts > pkt->pts) {
+            av_log(s, AV_LOG_WARNING, "Invalid DTS: %"PRId64" PTS: %"PRId64" in output stream %d:%d\n",
+                   pkt->dts, pkt->pts,
+                   ost->file_index, ost->st->index);
+            pkt->pts = AV_NOPTS_VALUE;
+            pkt->dts = AV_NOPTS_VALUE;
+        }
     }
     ost->last_mux_dts = pkt->dts;