minir | libretro frontend focusing on a native look

A homography is a projective transformation. As such it can only map straight lines to straight lines. The straight sides of your input curvilinear quadrangle are correctly rectified, but there is no way that you can straighten the curved sides using a projective transform.

In the photo you posted it may be reasonable to assume that the overall geometry is approximately a cylinder, and the "vertical" lines are parallel to the axis of the cylinder. So they are approximately straight, and a projective transformation (the camera projection) will map them to straight lines. The "horizontal" lines are the images of circles, or ellipses if the cylinder is squashed. A projective transformation will map ellipses (in particular, circles) into ellipses. So you could proceed by fitting ellipses. See this other answer for hints.

The reason they are not showing up is because the cursor's themselves are not defined, you'll have to define them by adding the cursor names at the end.

Here is a list of the cursor names:

It looks like inside your infinite loop you are adding to the queue and I'm guessing that you are adding data faster than it can be taken off of the queue by the other process.

You could check the queue size periodically from inside the infinite loop and if it is over a certain amount (say 500 items), then you could sleep for a few seconds and then check again.

https://docs.python.org/2/library/queue.html#Queue.Queue.qsize