Output information for Vector pass from Blender internal renderer

I’ve been trying to find somewhere that says just what values are being assigned to what colors of Blenders Vector pass. Does anyone know how the X/Y and movement information are being laid down by blender? Has anyone else successfully used the vector pass in a 3rd party tool of any kind?

the image (RGBA) is based on screen space pixel movement of verticies… R being the x direction from current frame to previous frame, G being y direction from current frame to next frame, B being x direction from current frame to next frame, A being y direction from current fram eto next frame.

I am not sure about 3rd party tools though…

The vector pass from Cinema4D and Blender are very similar. I did create an After Effects project that would extract the information from the C4D vector pass and route that information to a blur effect. This technique would probably work with a Blender vector pass as well.
http://www.videocopilot.net/forum/viewtopic.php?f=4&t=43138&p=175519&hilit=vector#p175519

so, its like the 3d normal maps, only dealing with actual movements rather than normal direction data?