'vorbis_fpu_setround' from 'os.h' does something weird. At least it does not do anything useful. It would probably make sense to have "andw" instruction instead of "orw" (to force rounding to nearest), but considering that the code was in a broken state for ages and nobody cared, does it even have any sense to have this function at all?

There is also SSE2 code and it does not have vorbis_fpu_setround counterpart (that would be only a problem if it is really needed of course).

Additional information to consider is that FPU performs rounding to nearest, but ties to even (for example, 0.5 is rounded to 0). It means that code 'return (int)floor(f+.5)' from the generic path is not completely identical to x87/SSE2 optimized versions.

A testcase attached.