I've a video h264+aac mkv 1280x720 mkv format. I encoded to xvid, mp3 in low resolution say 704x396

My steps are
1. mkvextract to extract the aac audio track from mkv
2.avisynth as input of mkv to encode to 704x396 in VDM
4. use audio convertion tools to convert aac to mp3 format
5. VDM to mux the mp3 audio and xvid video


However the final video is out-of sync with the audio

What's wrong ??

how does .avs look like?

It's been years since I last used VDM, but search for an option "harddup", or "hard duplicate frames" or "write duplicated frames into file no matter what" etc... Not sure if it helps. You could also use mencoder or derivatives.

DirectShowSource("video_1280_x264_aav.mkv",audio=false, fps=23.976,convertfps=true).lanczosresize(704,396)

how big is the desync? (is it the same all over the file, whats the difference in length between your mp3 and your new avi?)

there is a little strange on the audio file.
The length of extracted aac from the mkv is 25:00

But when I used conversion tool (Easy CD-DA Extractor) convert it to mp3, the length back to normal 24:54, same as the video length.