&gt; <i>&quot;Split image into 4 parts<p>My iMac has 2GB of GPU memory because it’s for home-use.
It’s insufficient size for larger image output.
It can output a little bit larger result when its display resolution set down to 640px x 480px.<p>It still needed to split images into 4 parts for 720p high quality video.<p>It caused a side effect which each frame has a border at the joint of the parts.&quot;</i><p>You seem to be correct on why the frame is split into four quadrants.