Audio kbps change after joining video

[V-Spec]

:confused:
After i join some mp3s with divx video, they change from 128 kbps to 127 kbps, but not all mp3s. What can i do to let them with 128 kbps after joining the video?
(I can't join two videos with different audio kbps)

[pureghetto]

Musicmatch has a function that converts audio files. It can also convert mp3s from one bitrate (is that the term?) to another.

off topic, but I've been pronouncing bitrate as bi-trate, and I just realised it means bit-rate when I wrote it in one word....lol

[V-Spec]

I already have the mp3 with the desired bitrate (128 kbps), but when i join it with a video, it changes to 127 kbps (inside the video).
The problem is, this doesn't happen to all mp3, and therefore i can't join several parts of a divx video. (some with 127 and some with 128)
:(