[foxyshadis]

If it helps, avisynth had its own problems with fps and ended up with this function to fix things up:

// This function uses continued fractions to find the best rational
// approximation that satisfies (denom <= limit).  The algorithm
// is from Wikipedia, Continued Fractions.
//
static void reduce_frac(unsigned &num, unsigned &den, unsigned limit)
{
  unsigned n0 = 0, n1 = 1, n2, nx = num;    // numerators
  unsigned d0 = 1, d1 = 0, d2, dx = den;  // denominators
  unsigned a2, ax, amin;  // integer parts of quotients
  unsigned f1, f2;        // fractional parts of quotients
  int i = 0;  // number of loop iterations

  while (1) { // calculate convergents
    a2 = nx / dx;
    f2 = nx % dx;
    n2 = n0 + n1 * a2;
    d2 = d0 + d1 * a2;

    if (f2 == 0) break;
    if ((i++) && (d2 >= limit)) break;

    n0 = n1; n1 = n2;
    d0 = d1; d1 = d2;
    nx = dx; dx = f1 = f2;
  }
  if (d2 <= limit)
  {
    num = n2; den = d2;  // use last convergent
  }
  else { // (d2 > limit)
    // d2 = d0 + d1 * ax
    // d1 * ax = d2 - d1
    ax = (limit - d0) / d1;  // set d2 = limit and solve for a2

    if ((a2 % 2 == 0) && (d0 * f1 > f2 * d1))
      amin = a2 / 2;  // passed 1/2 a_k admissibility test
    else
      amin = a2 / 2 + 1;

    if (ax < amin) {
      // use previous convergent
      num = n1;
      den = d1;
    }
    else {
      // calculate best semiconvergent
      num   = n0 + n1 * ax;
      den = d0 + d1 * ax;
    }
  }
}

Hopefully Intel would be kinder to this one, as well as giving smaller fractions.