I started playing around with ARCore through unity and testing on a Samsung galaxy S8.
Everything seems to be working fine but the video image that is displayed in the background (done automatically by ARCore) appears stretched vertically. I know the camera aspect on that device doesn't match the weird aspect of the phone's screen but I couldn't find a way to work around this.
This also happens when I build the small sample that comes with the ARCore package. Anyone else run into this?
Seems like a bug in the Unity implementation of ARCore according to this thread.
For those interested, We actually ended up doing fancy shader work to 'un-stretch' the image while pre-stretching all our content so we end up with a correct image - pretty ugly solution and I will happily yank this part out of the project as soon as a fix is issued.