lavf: use avg_frame_rate and packet number to exit find_stream_info

qatar does this too but clobbers the AVPacket.duration by approximate
values.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -2510,8 +2510,13 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
 
         st = ic->streams[pkt->stream_index];
         if (st->codec_info_nb_frames>1) {
-            int64_t t;
-            if (st->time_base.den > 0 && (t=av_rescale_q(st->info->codec_info_duration, st->time_base, AV_TIME_BASE_Q)) >= ic->max_analyze_duration) {
+            int64_t t=0;
+            if (st->time_base.den > 0)
+                t = av_rescale_q(st->info->codec_info_duration, st->time_base, AV_TIME_BASE_Q);
+            if (st->avg_frame_rate.num > 0)
+                t = FFMAX(t, av_rescale_q(st->codec_info_nb_frames, (AVRational){st->avg_frame_rate.den, st->avg_frame_rate.num}, AV_TIME_BASE_Q));
+
+            if (t >= ic->max_analyze_duration) {
                 av_log(ic, AV_LOG_WARNING, "max_analyze_duration %d reached at %"PRId64"\n", ic->max_analyze_duration, t);
                 break;
             }