I didn't immediately see this in the docs. We will make a FAQ for this. CC: @Luxonis-Karolina
But here it is from python3 depthai_demo.py -ff from the depthai repo (which is a demo repo):
https://github.com/luxonis/depthai
Notice that it crams the full aspect ratio of the color camera into the 1:1 aspect ratio of the neural model (which is 300x300 pixel resolution for this MobileNetSSDv2 example).
Looking for the config for this.