I finally watched your video.. that's the effect from the bitrate.. if you look at the log, the obtained bitrate is
which is very low. I'm not sure why you get such a low bitrate instead of the suggested one. I'll go check up on the snow commandlines again but at first glance I don't find anything wrong.
@edit: upon studying the supported commandline parameters posted in the snow thread, I don't find anything funny with your commandline. However, I encoded in two pass mode earlier today and the result was a big but black video. Now I've tried CQ mode and that seems to work out as it's supposed to. I'm now also trying another automated 2pass, with all the suggested settings by the authors (the 3 mbcomp modes at SSD, no m4v (that's a real speed killer.. I get 3 fps with, 11 fps without it), default prediction mode. I'll report again when I'm done.