Running ubuntu/linux on a xen server 6.5 with a passthrough GPU

For a while I was struggling to get ubuntu to work with my NVIDIA GPU in passthrough mode on xenserver. Xorg start, but then just fail... and those xorg messages are sooo helpful ;). Any way it turns out xorg could not correctly map the right driver to the correct PCI device. I had to add the PCI bus ID to the xorg.conf like here:

 BusID "PCI:0:12:0"

 Found this info here: https://wiki.archlinux.org/index.php/Xorg#More_than_one_graphics_card:

 my devices "lspci | grep -e VGA -e 3D":

00:02.0 VGA compatible controller: Cirrus Logic GD 5446
00:06.0 VGA compatible controller: NVIDIA Corporation GK104GL [Quadro K5000] (rev a1)

OpenCV GPU ORB issues

So I was noticing some issues with ORB on the GPU. The descriptors obtained at (in https://github.com/arcanon/raspbot/blob/master/video_reader.cpp):

                orbGpu(finalFrame, maskFrame, gpuKeyPoints, gpuDescriptors);
                orbGpu.downloadKeyPoints(gpuKeyPoints, keyPoints);

These were somewhat "unreliable" because there was no Gaussian blur before calculating the descriptor values. You could see this easily if you paused the video, so that the key points were always calculated on the same image. In this case, for the GPU the points jumped around while for the CPU they remain constant. This was fixed with
              orbGpu.blurForDescriptor = true;

This issue is well described at http://answers.opencv.org/question/10835/orb_gpu-not-as-good-as-orbcpu/.

The next step will be a stereo camera setup, so that I can filter out the background, which will help a lot filtering out false positives.

The other issue is that the camera has an exposure that is too long, this is a problem for the speed at which the detection happens. You can't move the robot to fast (or the objects can't move past the robot) because then they start to blur and then nothing is recognizable.