long answer, yes with and if
short answer, no with a but
Real Networks doesn't want you to do it, so it's very hard. The only way I know of is to play the file with Real Player, and re-capture the video from the screen. This is going to be a lossy conversion, to say the least, so you're going to want to use the very fastest computer you can get your hands on.
On a mac, it is basically only possible with
Snapz Pro. I haven't decided if you want to find a dual processor computer and play Real Player (in classic) and Snapz Pro X on the other, or if you should boot into OS 9 and lose the second processor, because real player seems to play a lot worse in classic than in 9 proper.
On Windows, you don't have to run a second program to capture the video, there is a crude command-line utility called
tinra, which stands for This Is Not Real Anymore. As far as I know, this method cuts out the fat of Real Player's GUI, but it still depends on Real Player's engine to play the original file in real time, so you still need the fastest computer you can find.
good luck