Efficient video saving for stationary cameras

Our stationary IP camera's image has most of time no action (I did not activate motion detection trigger). Even when there is movement it covers about 5% of the image:

To conserve space, develop an algorithm that only saves the changing portions of the video frames and plays them back smoothly. Write a web application that at prespecified time periods (e.g. every 0.25 seconds) grabs frames from camera's ip address and saves filtered data to a cloud storage.

Active noise cancellation project

Just phase shift original noise or characterize signal and invert it. FFT?

Update 13th Dec 2016:
Use smartphone mic and processing power to send noise cancelling signal to headphone. See reddit on why there are no noise cancelling apps:

...biggest one is that your cell phone microphone is monaural while noise cancelling headphone have to have two independent pickup channels to effectively cancel out the outside noise

App on Google Play: Noise Canceller

Geodesic Dome using PVC pipes

http://sketchupdate.blogspot.com.tr/2014/10/fabricating-pvc-geodesic-domes.html