VLC video converting for Xoom

I have a mkv HD video and I'm trying to watch it on my motorola xoom. I found some players but none of them was good enough to play my video smoothly. Then I read on the internet that I need to convert my video to mp4 in a certain format but I can't find a free converter that can do that for me. So I found out that VLC can convert the video for me but it takes too much time. I would like to know if someone have already converted hd videos using vlc and it played fine on the Xoom or if you have a better alternative free solution (I'm on a mac, so it'd be good to have a solution for mac).