mxf reader: convert_position rounding is not symmetrical
mxf reader: convert_position rounding is not symmetrical

kierank/bmxlib-bmx,xunchangguo/BMX,xunchangguo/BMX,Limecraft/ebu-bmx,Limecraft/ebu-bmx,xunchangguo/BMX,ebu/ebu-bmx,ebu/ebu-bmx,stuarthicks/bmx,Limecraft/ebu-bmx,stuarthicks/bmx,kierank/bmxlib-bmx,kierank/bmxlib-bmx,stuarthicks/bmx,ebu/ebu-bmx