Arduino based small LCD screen with camera video capturing
An Arduino doesn't have anywhere near the processing ability to transcode video from a camera unless you had an abysmal frame rate and very low quality. Even then, you would have to add extra storage because the Arduino would be over capacity in a heartbeat.

I recommend converting this project to a higher powered board like the Udoo. I have the Udoo Quad and it's beastly considering its form factor. You're going to need something a lot bigger than an Arduino!