MPG4 to AVI (Xvid & MPEG4)

[SeijoKoibito]

I'm trying to convert a video from MPEG4 to an .avi container and add subtitles (and reduce the filesize), yet nothing I do ends up doing anything other than running for a second or two, and resulting in a zero byte file. Also I noticed that under some subtitle burn options, in these attempts, refuse to let the position be changed from 80%, which is wayyyyy, to high.

There might be something wrong with the audio (even though it plays fine in over 8 apps), because of the log file output (which occurs in most attempts):
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Audio format 0x6134706d is incompatible with '-oac copy', please try '-oac pcm' instead or use '-fafmttag' to override it.
Selected video codec: [ffodivx] vfm: ffmpeg (FFmpeg MPEG-4)

I'm not certain exactly what this means, or how to fix it (and if there is a way to modify the burn position of the subtitles, if the GUI won't let me). Any help will be appreciated.

[Jacke]

If it's an MPEG-4 file (.mp4) it would probably contain AAC audio which won't normally go into an AVI file (which "-oac copy" would try to do). Set audio to MP3 and see what happens.

[SeijoKoibito]

I was really hoping not to lose audio quality, and I have seen several videos online claiming AAC in .avi containers.
I'll give it a shot.