I thought I was using the latest FFDShow (beta 7 r3154). That's what it says is the current version on the ffdhow-tryouts page.
I just got a new version (r3771). It does indeed output NV12 now
. I wish FFDShow had DXVA though. Without DXVA, my Radeon 5750 clocks up to full 3D clocks! I have to set clock speeds manually if I don't want that.
JanWillem32's test build just crashes for me