J-MOD2^{2}: Joint Monocular Obstacle Detection and Depth Estimation

In this work, we propose an end-to-end deep architecture that jointly learns to detect obstacles and estimate their depth for MAV flight applications. Most of the existing approaches either rely on Visual SLAM systems or on depth estimation models to build 3D maps and detect obstacles. However, for the task of avoiding obstacles this level of complexity is not required. Recent works have proposed multi task architectures to both perform scene understanding and depth estimation. We follow their track and propose a specific architecture to jointly estimate depth and obstacles, without the need to compute a global map, but maintaining compatibility with a global SLAM system if needed. The network architecture is devised to exploit the joint information of the obstacle detection task, that produces more reliable bounding boxes, with the depth estimation one, increasing the robustness of both to scenario changes. We call this architecture J-MOD$^{2}$. We test the effectiveness of our approach with experiments on sequences with different appearance and focal lengths and compare it to SotA multi task methods that jointly perform semantic segmentation and depth estimation. In addition, we show the integration in a full system using a set of simulated navigation experiments where a MAV explores an unknown scenario and plans safe trajectories by using our detection model

Recurrent Scene Parsing with Perspective Understanding in the Loop

Objects may appear at arbitrary scales in perspective images of a scene, posing a challenge for recognition systems that process images at a fixed resolution. We propose a depth-aware gating module that adaptively selects the pooling field size in a convolutional network architecture according to the object scale (inversely proportional to the depth) so that small details are preserved for distant objects while larger receptive fields are used for those nearby. The depth gating signal is provided by stereo disparity or estimated directly from monocular input. We integrate this depth-aware gating into a recurrent convolutional neural network to perform semantic segmentation. Our recurrent module iteratively refines the segmentation results, leveraging the depth and semantic predictions from the previous iterations. Through extensive experiments on four popular large-scale RGB-D datasets, we demonstrate this approach achieves competitive semantic segmentation performance with a model which is substantially more compact. We carry out extensive analysis of this architecture including variants that operate on monocular RGB but use depth as side-information during training, unsupervised gating as a generic attentional mechanism, and multi-resolution gating. We find that gated pooling for joint semantic segmentation and depth yields state-of-the-art results for quantitative monocular depth estimation

Deep learning based RGB-D vision tasks

Depth is an important source of information in computer vision. However, depth is usually discarded in most vision tasks. In this thesis, we study the tasks of estimating depth from single monocular images, and incorporating depth for object detection and semantic segmentation. Recently, a significant number of breakthroughs have been introduced to the vision community by deep convolutional neural networks (CNNs). All of our algorithms in this thesis are built upon deep CNNs. The first part of this thesis addresses the task of incorporating depth for object detection and semantic segmentation. The aim is to improve the performance of vision tasks that are only based on RGB data. Two approaches for object detection and two approaches for semantic segmentation are presented. These approaches are based on existing depth estimation, object detection and semantic segmentation algorithms. The second part of this thesis addresses the task of depth estimation. Depth estimation is often formulated as a regression task due to the continuous property of depths. Deep CNNs for depth estimation are trained by iteratively minimizing regression errors between predicted and ground-truth depths. A drawback of regression is that it predicts depths without confidence. In this thesis, we propose to formulate depth estimation as a classification task which naturally predicts depths with confidence. The confidence can be used during training and post-processing. We also propose to exploit ordinal depth relationships from stereo videos to improve the performance of metric depth estimation. By doing so we propose a Relative Depth in Stereo (RDIS) dataset that is densely annotated with relative depths.Thesis (Ph.D.) -- University of Adelaide,School of Computer Science , 201