We don't have the media ripping up and going yet. It is probably another week or two away yet since we're working on a media identification engine to id the cd or dvd and get cover art.
The formats may be the same. The size is just the size of the dvd. Single layer dvd's are under 5GB, and dual can be up to 9GB or so. I think most dvd's are something like 7. There's no compression -- it's just a raw copy of the disc. And when you play it, it's exactly like playing the real disc, with menus, subtitles, etc.
The code that mounts a ripped disc is in the src/Disk_Drive project, file Disk_Drive.cpp, function: bool Disk_Drive::mountDVD(string fileName, string &strMediaUrl)
You'll see the function: void Disk_Drive::CMD_Start_Ripping_DVD(string &sCMD_Result,Message *pMessage)
isn't implemented yet. That's where the ripping will go. I know it's just a single dd command, which is part of Linux, but don't have that in front of me at the moment.