DiPE: Deeper into Photometric Errors for Unsupervised Learning of Depth and Ego-motion from Monocular Videos

Unsupervised learning of depth and ego-motion from unlabelled monocular videos has recently drawn attention as it has notable advantages than the supervised ones. It uses the photometric errors between the target view and the synthesized views from its adjacent source views as the loss. Although significant progress has been made, the learning still suffers from occlusion and scene dynamics. This paper shows that carefully manipulating photometric errors can tackle these difficulties better. The primary improvement is achieved by masking out the invisible or nonstationary pixels in the photometric error map using a statistical technique. With this outlier masking approach, the depth of objects that move in the opposite direction to the camera can be estimated more accurately. According to our best knowledge, such objects have not been seriously considered in the previous work, even though they pose a higher risk in applications like autonomous driving. We also propose an efficient weighted multi-scale scheme to reduce the artifacts in the predicted depth maps. Extensive experiments on the KITTI dataset show the effectiveness of the proposed approaches. The overall system achieves state-of-the-art performance on both depth and ego-motion estimation.