Fixing corrupted avi & ac3

[Spindoctor]

I am trying to burn DVD's from avi files but some of these files are corrupted in the middle causing the video to scramble. That however isn't the main problem, but when demuxing the ac3 soundtrack using nandub and then fixing it with BeSweet, Besweet strips out the corrupted frames and leaves an out of sync ac3 file.

How do I produce an ac3 file which keeps the same length by fixing the error frames or putting in silences?