I tried, for a laugh, 640x384, 23fps,+/-400kbps and found it to be chopping up every ten seconds or so. The 400x240 ones OTOH play beautifully at almost any bitrate (I tend to go for lower rates to reduce file sizes; it's not as if I'm expecting home theatre results on a portable player anyway). I did switch from Media Converter to VirtualDub (Xvid codec) for my re-encoding.