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

Scale-Adaptive Neural Dense Features: Learning via Hierarchical Context Aggregation

How do computers and intelligent agents view the world around them? Feature extraction and representation constitutes one the basic building blocks towards answering this question. Traditionally, this has been done with carefully engineered hand-crafted techniques such as HOG, SIFT or ORB. However, there is no ``one size fits all'' approach that satisfies all requirements. In recent years, the rising popularity of deep learning has resulted in a myriad of end-to-end solutions to many computer vision problems. These approaches, while successful, tend to lack scalability and can't easily exploit information learned by other systems. Instead, we propose SAND features, a dedicated deep learning solution to feature extraction capable of providing hierarchical context information. This is achieved by employing sparse relative labels indicating relationships of similarity/dissimilarity between image locations. The nature of these labels results in an almost infinite set of dissimilar examples to choose from. We demonstrate how the selection of negative examples during training can be used to modify the feature space and vary it's properties. To demonstrate the generality of this approach, we apply the proposed features to a multitude of tasks, each requiring different properties. This includes disparity estimation, semantic segmentation, self-localisation and SLAM. In all cases, we show how incorporating SAND features results in better or comparable results to the baseline, whilst requiring little to no additional training. Code can be found at: https://github.com/jspenmar/SAND_featuresComment: CVPR201

Play and Learn: Using Video Games to Train Computer Vision Models

Video games are a compelling source of annotated data as they can readily provide fine-grained groundtruth for diverse tasks. However, it is not clear whether the synthetically generated data has enough resemblance to the real-world images to improve the performance of computer vision models in practice. We present experiments assessing the effectiveness on real-world data of systems trained on synthetic RGB images that are extracted from a video game. We collected over 60000 synthetic samples from a modern video game with similar conditions to the real-world CamVid and Cityscapes datasets. We provide several experiments to demonstrate that the synthetically generated RGB images can be used to improve the performance of deep neural networks on both image segmentation and depth estimation. These results show that a convolutional network trained on synthetic data achieves a similar test error to a network that is trained on real-world data for dense image classification. Furthermore, the synthetically generated RGB images can provide similar or better results compared to the real-world datasets if a simple domain adaptation technique is applied. Our results suggest that collaboration with game developers for an accessible interface to gather data is potentially a fruitful direction for future work in computer vision.Comment: To appear in the British Machine Vision Conference (BMVC), September 2016. -v2: fixed a typo in the reference

Exploring Subtasks of Scene Understanding: Challenges and Cross-Modal Analysis

Scene understanding is one of the most important problems in computer vision. It consists of many subtasks such as image classification for describing an image with one word, object detection for finding and localizing objects of interest in the image and assigning a category to each of them, semantic segmentation for assigning a category to each pixel of an image, instance segmentation for finding and localizing objects of interest and marking all the pixels belonging to each object, depth estimation for estimating the distance of each pixel in the image from the camera, etc. Each of these tasks has its advantages and limitations. These tasks have a common goal to achieve that is to understand and describe a scene captured in an image or a set of images. One common question is if there is any synergy between these tasks. Therefore, alongside single task approaches, there is a line of research on how to learn multiple tasks jointly. In this thesis, we explore different subtasks of scene understanding and propose mainly deep learning-based approaches to improve these tasks. First, we propose a modular Convolutional Neural Network (CNN) architecture for jointly training semantic segmentation and depth estimation tasks. We provide a setup suitable to analyze the cross-modality influence between these tasks for different architecture designs. Then, we utilize object detection and instance segmentation as auxiliary tasks for focusing on target objects in complex tasks of scene flow estimation and object 6d pose estimation. Furthermore, we propose a novel deep approach for object co-segmentation which is the task of segmenting common objects in a set of images. Finally, we introduce a novel pooling layer that preserves the spatial information while capturing a large receptive field. This pooling layer is designed for improving the dense prediction tasks such as semantic segmentation and depth estimation