how to setup to better audio quality -higher than only 64kbi

hi.. i m new here...

i just tried to use the Kdenlive video editor because i was looking for an converter for the mpeg4 H264 and found this nice app...
my short 12min (music-) video was successful but when i did listen to it the sound was quite bad, it has only 64kbit in stereo. we can hear the artifakes on the sound..

how can i change the sound to better quality one?

for me all is good even change config files on the Kdenlive tio get better audio quality

i use the xvid with 756x525 (TV res/quality) also it will be cool that we could change the sound codec from AC3 to mp3 or so.. but i dont know how to do it.

i use Ubuntu 7.04