Encoding MP3 causes the sample length to CHANGE?

[Colmino]

This one baffles me. Every time I encode an MP3 with Adobe Audition, it pads the sample length - it actually resamples the audio during encoding. The anomaly varies, without apparent pattern. The difference seems very slight (less than 4/100ths of a percentile), but as I'm trying to integrate the audio into a video lasting five minutes, even that slight difference becomes frustratingly apparent. It doesn't make a difference what my quality settings are, or whether I choose VBR or CBR. As an example, a recent audio file I had, which clocked in at 15500613 samples, ended up as a CBR MP3 clocking in at 15505871 samples. And yes, I checked the chronological positions of specific peaks near the beginning and end of the two sample specimens and confirmed that the entire sample had indeed been resampled during encoding.

What is going on here? Is this not digital information? How can a dramatic failing like this even exist? If it's bad for a five minute video, it's got to be a staggering deal-breaker for anything longer; the results would be patently unusable.

I guess my questions are: 1) Is there a way of forcing Audition to generate a PROPER MP3? And 2) if not, is there an encoding app out there which is actually capable of doing so?

Thanks.

[manono]

if not, is there an encoding app out there which is actually capable of doing so?

BeSweet, HeadAC3he, both free.