AC3 Problem Converting HDTV to Xvid

Hi all, I’m very much a n00b whenit comes to divx/xvid.
I was trying to convert an HDTV mpeg2 video with ac3 track (1920x1088i) to an xvid avi which can be stored on a dvd5 (1280x720) using AutoGK.
The video conversion at this resolution is spectacular, unbeleivable quality considering file size, however the ac3 stream on the converted video gets messed up, comes out stereo without center channel mixed in. I specifically used the ac3 option in autoGK and encoded twice with the same results.

I then demuxed the ac3 track using tmpgenc plus and the ac3 track by itself plays as it should. I cannot find a way to remux the xvid with the isolated working ac3 track. Is there a way? I apologize if this has been covered but having searched the net all day I can’t seem to find the info.
Also, is there a somewhat simple way to convert to 1280x720 mpeg2? Since xvid/divx/svcd is not a neccessity, it would make remuxing the file easier for me.

I solved my problem using AVI-Mux to add the original ac3 stream to the avi. I still have a whole lot to learn :iagree: