On linux you can rotate the camera image using the v4l2-ctl tool. For example v4l2-ctl --set-ctrl=rotate=180 rotates the image by 180°.

Put this command into the /etc/sv/hkcam/run script just before hkcam binary is executed.

#!/bin/sh -e
exec 2>&1
v4l2-ctl --set-ctrl=rotate=180
exec hkcam --data_dir=/var/lib/hkcam/data --verbose=true

On linux you can set the video size with v4l2-ctl --set-fmt-video=width=1280,height=720,pixelformat=YU12.

Put this in the /etc/sv/hkcam/run script

#!/bin/sh -e
exec 2>&1
v4l2-ctl --set-fmt-video=width=1280,height=720,pixelformat=YU12
exec hkcam --data_dir=/var/lib/hkcam/data --verbose=true