- MPEG4/DivX has a maximum value of 65535 for the timebase denominator.
- MPEG1 and 2 have a list of supported frame rate ratios. These use
ratios like 24000/1001 and need those exact numbers.
This fixes an issue introduced in c5b1e7cd4e
where the correct ratio was passed to FFmpeg, but not with the identical
numbers FFmpeg has in a lookup table.