Converting movies into real player format

i have hundreds of movies that i've been ripping to my hard drives and recently i've downloaded some movies in RM format. the real player files are heaps smaller and from what i can see with minimal loss of quality, can anyone tell me how i should go about converting avi's and/or dvd files into the real player format? and what programs are the best to use, i've spent a lot of time ripping dvd's and music so i know a lot about it and interested in learning about this way of doing things, so a point in the right direction will be greatly appreciated.