Perspective texture mapping

Hi all, go easy on me i’m new to this forum (not openGL though!)

I’m having some issues with trying to do some perspective textureing, i’ve been working on the problem for a few days and i’m doing something daft and cant work out what it is so i guess here i’m just after conformation that i’m indeed not going bonkers !

Ok, so heres the scene.

i have a frame of video for which i know all the camera parameters for the scene such that i can draw things in the right perspective for the frame of video on the video.
I can draw a rectangle in the image (2d Screen space) and i assume that the bottom of the rectangle i have drawn is on the ground plane meaning i can turn the screen space drawn rectangle into a 3D billboard. I save the bit of video within the region i have drawn as a texture.

So at this point just to clarify i have a bit of texture obtained from the video and a 3D quad that corresponds to my bit of texture.

I want to draw the texture with the correct perspective onto my 3D quad such that it matches the underlying video, i’m doing something daft here though as when i try this my texture sprites don’t quite match the underlying video they were generated from when i draw them on the quads.

heres a bit of psuedo code of what i’m doing.

glTranslated(to the centre of my texture in texture coords);
glScaled(to scale & bias my texture to its correct size)
gluPerspective(using my camera parameters that i know when the texture was generated);
gluLookAt(using my cameras position, look at point and up vector)

i then draw my quad with the 3D coordinates for both the quad and the texture coordinates.

If anyone has a clue about what i’m doing or trying to do and can either point me in some direction for further info or tell me what bonkers thing i’m doing wrong then i would be very greatful as this is makeing me crazy !

Many thanks