avformat/matroskaenc: Avoid floats in default duration calculation

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/matroskaenc.c

@@ -926,10 +926,10 @@ static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,
         put_ebml_uint(pb, MATROSKA_ID_TRACKTYPE, MATROSKA_TRACK_TYPE_VIDEO);
 
         if(   st->avg_frame_rate.num > 0 && st->avg_frame_rate.den > 0
-           && 1.0/av_q2d(st->avg_frame_rate) > av_q2d(codec->time_base))
-            put_ebml_uint(pb, MATROSKA_ID_TRACKDEFAULTDURATION, 1E9 / av_q2d(st->avg_frame_rate));
+           && av_cmp_q(av_inv_q(st->avg_frame_rate), codec->time_base) > 0)
+            put_ebml_uint(pb, MATROSKA_ID_TRACKDEFAULTDURATION, 1000000000LL * st->avg_frame_rate.den / st->avg_frame_rate.num);
         else
-            put_ebml_uint(pb, MATROSKA_ID_TRACKDEFAULTDURATION, av_q2d(codec->time_base)*1E9);
+            put_ebml_uint(pb, MATROSKA_ID_TRACKDEFAULTDURATION, 1000000000LL * codec->time_base.num / codec->time_base.den);
 
         if (!native_id &&
             ff_codec_get_tag(ff_codec_movvideo_tags, codec->codec_id) &&