avformat/avidec: allow rounding errors between scale/rate and timebase

Fixes Ticket3670
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/avidec.c

@@ -1780,8 +1780,7 @@ static int avi_read_seek(AVFormatContext *s, int stream_index,
             continue;
 
 //        av_assert1(st2->codec->block_align);
-        av_assert0((int64_t)st2->time_base.num * ast2->rate ==
-                   (int64_t)st2->time_base.den * ast2->scale);
+        av_assert0(fabs(av_q2d(st2->time_base) - ast2->scale / (double)ast2->rate) < av_q2d(st2->time_base) * 0.00000001);
         index = av_index_search_timestamp(st2,
                                           av_rescale_q(timestamp,
                                                        st->time_base,