ignore duration of the first 2 frames in the max-time break check

fixes framerate detection for framerate_misdetected.wmv

Originally committed as revision 7384 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/utils.c

@@ -1880,7 +1880,8 @@ int av_find_stream_info(AVFormatContext *ic)
         read_size += pkt->size;
 
         st = ic->streams[pkt->stream_index];
-        st->codec_info_duration += pkt->duration;
+        if(st->codec_info_nb_frames>1) //FIXME move codec_info_nb_frames and codec_info_duration from AVStream into this func
+            st->codec_info_duration += pkt->duration;
         if (pkt->duration != 0)
             st->codec_info_nb_frames++;