Convert between MATLAB stereoParameters and OpenCV stereoRectify stereo calibration

Question

I wish to convert a MATLAB stereoParameters structure to intrinsics and extrinsics matrices to use in OpenCV\'s stereoRectify.

If I understood http://docs.opencv.org/2.4

Answer 1

https://stackoverflow.com/a/28317841 gives the formula for the Q matrix:

Tx is from matrix T. cx, cy and cx' are from the camera matrices. f is some sensible combination of their x and y focal lengths.

Still dunno how to get P1, P2, R1 and R2 though. Anybody?