refuses to enconde in AC3

[DeusExMachina]

I have tried about 5 times to encode an ~700MB .avi file (MPEG4, 512x384 video 192kbps/48000Hz audio) file to MPEG-2(352x480)/AC3 audio. I have tried using the quick presets then fiddling with audio parameters, and not using presets and just entering the parameters manually, and each time after 24 hours of encoding (yeah, my machine is SLOW) I get a video file with the right video, but mp2 audio. What's the deal. Why will it not let me get AC3? I wouldn't case too much, but
1) I swear it did not use to do this, and
2) the mp2 is not the right size (5 minutes missing from the end and not loses sync in the middle

What gives?

[major]

Are you possibly using the "Decode with mplayer" option? If yes, it only supports mp2 currently.

[DeusExMachina]

As usual, you hit the nail on the head! (maybe there should be an error message alert or the option for AC3 grayed out if the mplayer option is being used?) The issue that caused me to chose that option, however was that the quicktime codec for some reason was generating a file that DVD studio pro was not able to import. Perhaps I will try to keep the elementary streams from the quicktime results and try those.
As usual, thanks a lot.

[DeusExMachina]

OK, now I remember why I didn't use quicktime. after it successfully encodes the video, it chokes on the audio, making a 0k ac3 file and then chokes on the mux. Any idea why the quicktime encoder can't seem to work on the AC3? It is there, i know, since it plays in VLC

[DeusExMachina]

Although, it would appear that one work around is to open in DDII, which, since it has little support for AC3, just dumps the audio, which, incidentally, appears to be the correct length.

[TugBoat]

My normal procedure is to encode with the ffmpeg MPEG2 codec and not concern myself with what materializes for an audio track. I never use the Decode with QT option. If the AVI has an AC3 track that I want to use, I then open the original AVI, set the 'Movie Audio to AC3' preset, select 'passthrough' and use that audio in DVDSP. You do have to change the extension though. It gives something like .avi.ff.cc, change it to .ac3 and all is well. If the audio track is something else, I open the AVI in QT Pro and export an AIFF for A.Pack. Works everytime.