I am using a custom camera to record footage and estimate 3d human body pose using Maxine AR SDK BodyTrack.
I saw in the SDK source code that the camera focal length was mentioned but never changed and used some logitech webcam with focal length value 800.f.
What units you are using ? According to the numbers it looks like pixels but how do you calculate it ?
According to my knowledge focal length should be in mm. For instance, I have a camera with focal length 2.1002 mm and pixel size 0.004mm for resolution 1280x720. It was calculated according to the following formula
f_mm = (fx+fy) / 2 * pixel_size_mm
(530.19 + 529.91) / 2 * 0.004 = 2.1002 mm
I have chosen ZED 2 camera, left one.
Focal Length parameter is used to build the camera intrinsic matrix using the focal length (fx and fy) and principal offsets (ox and oy). Internally, this is used to the compute the 3D coordinates of the keypoints for 3D Body Pose. The Focal Length value is either setup by the user or the default value of 800.79041 is set for fx and fy. ox and oy are computed based on the image size as they are the principal offsets.