Visual Odometry on YouTube Videos

Is there any simple or complicated approach to do any kind of visual odometry on youtube videos? A very rough approximation is enough, it is only a hint for my algorithm. The big problem is that I don't have any camera intrinsics. So either they should be learned/predicted (a dream) or the approximation can be even rougher. There is a new paper (https://arxiv.org/abs/1904.04998) from google that basically does this. But the code is not available and redoing what they did is not feasible for me. A simple opencv optical-flow based solution would already be enough, if it does not rely on camera intrinsics.