If you are having problems with audio sync after DLing Xvid, Divx from the net and trying to encode the video to MPEG-2 for a DVD:

TRY THIS METHOD: (And there are others.)

Drop it into VirtualDub Mod. VD Mod will tell you immediately if you have MP3 VBR audio.

If it's MP3 VBR then: https://forum.videohelp.com/viewtopic.php?t=280779

This will get your VBR audio out and save it as a WAV audio file.

If you use a encoder like TMPGEnc that accepts elemental streams, just use the WAV as your audio source, along with your original video. You should end up with MPEG 1, Layer 2 audio for default. Good for PAL video, works on most NTSC DVD players. Then author the file to DVD format with a authoring program.

OR BETTER, IMO: Take the new WAV file and put it into ffmpeggui and convert it to AC3 audio. Convert the video only to MPEG-2 with a encoder like TMPGEnc. Use this audio as the audio source with TMPGEnc DVD Author when you author to DVD, along with the encoded MPEG-2 video.

OR IF YOU WANT TO COMBINE YOUR NEW AUDIO BACK WITH YOUR ORIGINAL VIDEO:

In VD Mod, in 'Streams' again, open the Stream list. Select 'add'. Add your new audio. This can be WAV or AC3 or MP3. (After being converted to MP3 CBR with VD Mod. You can also do this with a freeware program like Audacity if you want to filter the audio.)

Move this new audio to the top of the list. Select the old audio. Select 'Delete'. This will not damage the original video. Click 'OK'

Then in 'Video', select 'Direct stream copy' and then 'Save As...' in Edit. Use a new filename.
This will save the video with no modifications, along with the new audio. You can use this new video file with some encoder programs that don't accept elemental streams like DivxToDVD or similar. With DivxToDVD, the WAV audio works fine, just mux it back in and encode the result with DivxToDVD.

I probably left out a lot. This is a work in progress.