Putting Screenshots from Videos into an Array

I have a set of 3 videos and would like to take four screenshots from each one at the same times (ie. frames) to put into a 3x4 array of images, what would be the easiest way to do this on MATLAB?

The files are saved both as .avi and .cihx files from a high-speed video camera.

[Jonas]

have a look into the comment under the answer of https://de.mathworks.com/matlabcentral/answers/92920-how-do-i-read-in-an-avi-frame-and-save-it-to-an-image-file-in-matlab