As I have no previous knowledge of video editing, I'm still struggling to get ffmpeg to work as I need.
I need to resize a video of any size and any aspect ratio to height a of 960px, then crop both sides to get a square of 960x960 where the original image would be centered. And now the tricky part for me, I need to duplicate this square, so they would be side by side as single output video of 1920 x 960 pixels.
It's not supposed to be 3D, only cardboard friendly.