Roku: Thumbnails look pixelated

How to fix thumbnail pixelated issue and show like real image? I am developing (app) channel for Roku using scene graph. I created more then one Grid by Markup Grid node and display thumbnail, the thumbnails look pixelated or stretch.

So this is continuation of the SO question.
I am puzzled that the images there are 1324x882 dimensions, which is a 1.5 = 3:2 ratio. That does not seem right, what’s going on? Were it a typical wide screen, it would be 16:9 (1280/720 = 1.78). Might be going to a strange capture device?