Efficient Scene Parsing with Imagery and Point Cloud Data

Scene parsing, aiming to provide a comprehensive understanding of the scene, is a fundamental task in the field of computer vision and remains a challenging problem for the unconstrained environment and open scenes. The results of scene parsing can generate semantic labels, location distribution, as well as for instance shape information for each element, which has shown great potential in the applications like automatic driving, video surveillance, just to name a few. Also, the efficiency of the methods determines whether it can be used on a large scale. With the easy availability of various sensors, more and more solutions resort to different data modalities according to the requirements of the applications. Imagery and point cloud are two representative data sources. How to design efficient frameworks in separate domains remains an open problem and more importantly, lays a solid foundation for multimodal fusion. In this thesis, we study the task of scene parsing under different data modalities, i.e., imagery and point cloud data, by deep neural networks. The first part of this thesis addresses the task of efficient semantic segmentation in 2D image data. The aim is to improve the accuracy of small models while maintaining their fast inference speed without introducing extra computation overhead. To achieve this, we propose a knowledge-distillation-based method tailored for semantic segmentation to improve the performance of the small Fully Convolution Network (FCN) model by injecting compact feature representation and long-tail dependencies from the large complex FCN model (incorporated in Chapter 3). The second part of this thesis addresses the task of semantic and instance segmentation on point cloud data. Compared to rasterized image data, point cloud data often suffer from two problems: (1) how to efficiently extract and aggregate context information. (2) how to solve the forgetting issue Lin et al., 2017c caused by extreme data imbalance. For the first problem, we study the influence of instance-aware knowledge by proposing an Instance-Aware Module by learning discriminative instance embedding features via metric learning (incorporated in Chapter 4). We also address the second problem by proposing a memory-augmented network to learn and memorize the representative prototypes that cover diverse samples universally (incorporated in Chapter 5).Thesis (Ph.D.) -- University of Adelaide, School of Computer Science, 202