Directshow filter that supports ac3 in mp4?

I have some mp4s that play fine in VLC, but I want to author a DVD using them... I can't get the audio (it's silent).

I think it's because some monkey put 5.1 AC3 audio inside the mp4 instead of AAC... So I can either demux, reencode, and remux, or just use a directshow filter so the authoring app doesn't know the difference (hopefully).

??

try this: http://ffdshow-tryout.sourceforge.net/ I just use it to play 24 bit wavs in media player but it has tons of filters

I decided to just take the ac3 stream out and select that file as the audio track. When I tried to mix it down to mp3 or aac, it wouldn't work due to copy protection (!?)

So now my dvd has 5.1 audio after all...