avformat/utils: Be slightly more tolerant with fps vs. stream timebase

Fixes regression with ticket2451
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/utils.c

@@ -3096,7 +3096,8 @@ void ff_rfps_calculate(AVFormatContext *ic)
             for (j= 0; j<MAX_STD_TIMEBASES; j++) {
                 int k;
 
-                if (st->info->codec_info_duration && st->info->codec_info_duration*av_q2d(st->time_base) < (1001*12.0)/get_std_framerate(j))
+                if (st->info->codec_info_duration &&
+                    st->info->codec_info_duration*av_q2d(st->time_base) < (1001*11.5)/get_std_framerate(j))
                     continue;
                 if (!st->info->codec_info_duration && get_std_framerate(j) < 1001*12)
                     continue;