mplayer wants portrait mode?

[Dieter BSD]

FreeBSD 8.2  amd64
MPlayer SVN-r32577-snapshot-4.2.1  from packages

> VO: [xv] 1280x720 => 1280x720 Planar YV12
> Source image dimensions are too high: 1280x720 (maximum is 720x2048)

mplayer -vo x11
gets past this, but then reports that the cpu is too slow.

Question is, why is the maximum 720x2048 rather than 2048x720?
Does it really want portrait mode?