Do not fill the pts reordering buffer with guessed dts.

These values should not matter at all in principle because they
do not correspond to the time of display of any frame but it seems
ffmpeg becomes confused by them if they are far off and its not
strictly correct to set them to guessed values.
Fixes video_stalls_at_start.wmv

Originally committed as revision 14746 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/utils.c

@@ -898,8 +898,6 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
 
     if(pkt->pts != AV_NOPTS_VALUE && delay <= MAX_REORDER_DELAY){
         st->pts_buffer[0]= pkt->pts;
-        for(i=1; i<delay+1 && st->pts_buffer[i] == AV_NOPTS_VALUE; i++)
-            st->pts_buffer[i]= (i-delay-1) * pkt->duration;
         for(i=0; i<delay && st->pts_buffer[i] > st->pts_buffer[i+1]; i++)
             FFSWAP(int64_t, st->pts_buffer[i], st->pts_buffer[i+1]);
         if(pkt->dts == AV_NOPTS_VALUE)