PPB_MULT
tmp = calibration * (s64)PPB_MULT;
tmp -= PPB_MULT / 2LL;
tmp += PPB_MULT / 2LL;
tmp = div_s64(tmp, PPB_MULT);
tmp = calibration * PPB_MULT;
tmp -= PPB_MULT / 2LL;
tmp += PPB_MULT / 2LL;
tmp = div_s64(tmp, PPB_MULT);