ac3 6-c downmix to ac3 2-c

[cnterr]

I've 13 short movie with audio in ac3 2 channel format and 1 short movie with audio in ac3 6 channel format. I can't create a single DVD video with TMPGEnc DVD Author because the last movie have a track non compatible (6 channel) with other movie.
I've extracted track and I've obtained a file .ac3. Now! Hov can downmix this ac3 file without convert it in Wav or other audio format?

[zodiac]

http://www.doom9.org/ac3machine.htm

[Skynet107]

BeSweetGUI will also do the job for you. Why not get a hold of DVD-Lab and author the DVD with both audio tracks untouched.

BeSweetGUI