The only time I saw video on BlackBerry was .jam files (Java movie) that were originally designed for other J2ME cellphones than the BlackBerry. (You can install midlets on BlackBerry too, like a Nokia cellphone java video on a BlackBerry)
From the BlackBerry video that I have seen, I should mention realistically, for a player, for simple 2/3rd screen video, expect only 2-3 frames per second on most BlackBerries, with about maybe up to 10 frames per second on the new model 7250, which has the fastest CPU. These are only rough guesstimates, though.
BlackBerry Benchmarks
http://www.blackberryforums.com/viewtopic.php?t=4269
All future BlackBerries will have faster CPU's so you may have a lead time writing a video player. It is kind of early, BlackBerry is not yet quite ready for video, but the CPU and network is "getting there". If, and when, an EV-DO upgrade is released for the BlackBerry model 7250, you could probably stream video realtime at semi-smooth framerates on a 7250!
There's a gotcha: You cannot do custom audio on any BlackBerry yet. So you'd have video with no audio. Unless RIM releases an upgrade that fixes this for the newer models of BlackBerries (the 32meg-plus models).
Again, it's kind of early to begin writing a video player.... but I can vouch that it's going to "get there".
video player?
