lavf: add a "warning" when discarding a oddly backward subtitle or data starttime

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

libavformat/utils.c

@@ -2063,6 +2063,9 @@ static void update_stream_timings(AVFormatContext *ic)
     }
     if (start_time == INT64_MAX || (start_time > start_time_text && start_time - start_time_text < AV_TIME_BASE))
         start_time = start_time_text;
+    else if(start_time > start_time_text)
+        av_log(ic, AV_LOG_VERBOSE, "Ignoring outlier non primary stream starttime %f\n", start_time_text / (float)AV_TIME_BASE);
+
     if (start_time != INT64_MAX) {
         ic->start_time = start_time;
         if (end_time != INT64_MIN)