XDVD and XSVCD MPG files

[Charles Martin]

Thanks for the great help on my last question, now here's a new one:

I've gotten some music videos off Usenet that are MPG files, but they 
are XDVD and XSVCD mpg files and, while I can play them (with some 
weird artifacts) so I know they are MPEG-2, I can't figure out a way to 
convert them to "normal" SVCD-ready MPEG-2 files so that I can create 
SVCDs of them.

I have tried feeding these files directly to ffmpeg X, but it doesn't 
like them. If anyone's been working with XSVCD and XDVD mpeg files and 
feels like either emailing me or pointing me to a tutorial, it's 
appreciated.

Thanks
Chas