I have been using the great Pixelcontroller software to capture moving image from my laptop screen and sending it to a teensy3 led pixel array. The pixelcontroller software is free, and you can get it here:
to set it up for screen grab in real time so that you can display video and whatever is on your screen on the pixel array you need to do a couple of things first:
for screen capture using pixelcontroller, you need to enable first as it is set to disabled by default. There are two parts to this:
1) the config file needs to allow it to happen
2) then you can choose to use it by selecting the source option whilst pixelcontroller is running.
To set the config.properties file correctly go to this section of the file:
#default values for generators
#x/y offset for screen capturing generator
#if you define screen.capture.window.size.x as 0, the screen capture generator will be disabled
make sure you remove the # sign in front of any of the screen.capture lines, and change x=0 to something like x=100.
save the config file
Then, when you restart pixelcontroller, go to the first source controller (the pink arrow shows the one I mean), labelled blinkenlight by default, select the source by clicking on the currently selected source (blinkenlight) and select Screen capture.
you will then see a red capture square. Here is a video: