Problem downmixing audio

I’m encoding my DVDs into MP4, and I’ve been having a lot of trouble with the audio. Every time I try to encode it, it’s too low.

First I tried using Nero Recode. After I had problems with it, I gave up and started using MeGUI and the Nero AAC encoder (along with MP3 to see if it would give me different results), but I’m still having the same problem. If I encoded the audio but left the channels alone, it would be the same volume as the source.

I know I could encode the audio with another program and raise the volume level (would be too much work for what it’s worth) or use fddshow/ac3filter (more CPU usage, doesn’t actually fix the problem).

Anyone have any recommendations?