avformat/utils: Discard huge timestamps which would cause overflows if used in basic computations

Allowing larger timestamps makes it impossible to calculate basic things like the
difference of 2 timestamps or their sum without checking each individual computation for
overflow.
This should avoid a significant number of overflow checks

Fixes Ticket5136
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/utils.c

@@ -833,6 +833,12 @@ int ff_read_packet(AVFormatContext *s, AVPacket *pkt)
             continue;
         }
 
+        if (   (pkt->dts != AV_NOPTS_VALUE && (pkt->dts <= INT64_MIN/2 || pkt->dts >= INT64_MAX/2))
+            || (pkt->pts != AV_NOPTS_VALUE && (pkt->pts <= INT64_MIN/2 || pkt->pts >= INT64_MAX/2))) {
+            av_log(s, AV_LOG_WARNING, "Ignoring huge timestamps %"PRId64" %"PRId64"\n", pkt->dts, pkt->pts);
+            pkt->dts = pkt->pts = AV_NOPTS_VALUE;
+        }
+
         st = s->streams[pkt->stream_index];
 
         if (update_wrap_reference(s, st, pkt->stream_index, pkt) && st->pts_wrap_behavior == AV_PTS_WRAP_SUB_OFFSET) {