Blender camera projection matrix?

Howdy all,
Back with another question we can’t figure out on our own. We need to find where can we find the source code for how the projection matrix is built for a blender camera?

The situation is we are building a blender to XNA camera system for for animating game cutscenes in blender with the fine camera control that blender allows compared to anything easily cooked up in XNA. Location and rotation seem to translate perfectly, even the noise modifier (keyable in 2.6 por favor devs!) but the “lens” appears to be off. everything is a bit further off as if the lens in XNA is wider. In order to remedy this we think we need teh aforementioned info to compare where things are different and tweak em’

EDIT: Does anyone know if the “lens” option refers to the width or height of the camera parameters? I have the render settings set to 1280/720 so I had an idea of what framing for widescreen would be like, but now I wonder if that isn’t screwing it up somehow.

Cheers good fellows!

Also, any help or pointers towards enlightening us dummies is greatly appreciated, even if it has nothing to do with what we are looking for, we’re not even sure that’s the “problem”