No, compression with 99.9% of AVI codecs a lossy process and you'll never be able to get back to the original video. (unlike a zip file for example.)
if there is a better place to ask such a basic question pleas let me know.
any mpg-1 or mpg-2 file converted to avi no matter how small the file is compressed, can always be restored to its ariginal state, yes, no?
i did not know that. but that is very interesting. if so what is the point in converting a avi (lets say around 780 meg), to a mpg vbr 3000 at 4 gig? it can't recreate something that isn't there right? so why so much bigger of a file,.. algorithm?
also what about mpg. same thing? should i expect a 1.5 gig mpg, converted off a 9 gig cd will never get any better then what it alread looks like?
It's all about standards. For example, if you have an album in mp3 format and you burn it to CD, it's going to take way more space just to fit into the CD standard.
Same with an AVI that's in MPEG4 like DivX or XviD... if you convert it to the SVCD standard or the DVD standard it's going to take up more space. You won't gain any quality though, you're quite right about that.