This paper documents the winning entry at the CVPR2017 vehicle velocity estimation challenge. Velocity estimation is an emerging task in autonomous driving which has not yet been thoroughly explored. The goal is to estimate the relative velocity of a specific vehicle from a sequence of images. In this paper, we present a light-weight approach for directly regressing vehicle velocities from their trajectories using a multilayer perceptron. Another contribution is an explorative study of features for monocular vehicle velocity estimation. We find that light-weight trajectory based features outperform depth and motion cues extracted from deep ConvNets, especially for far-distance predictions where current disparity and optical flow estimators are challenged significantly. Our light-weight approach is real-time capable on a single CPU and outperforms all competing entries in the velocity estimation challenge. On the test set, we report an average error of 1.12 m s which is comparable to a (ground-truth) system that combines LiDAR and radar techniques to achieve an error of around 0.71 m s.
In @cite_38 a semi-supervised approach is described that provides a fusion between using sparse ground truth data from a LiDAR sensor and stereo view synthesis, estimating one image in a stereo pair from the other, to infer dense depth maps. Others @cite_15 @cite_26 in turn rely solely on stereo as a supervision signal, which comes with the benefit of easily available or obtainable data.
@cite_38 @cite_15 @cite_26
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Supervised deep learning often suffers from the lack of sufficient training data. Specifically in the context of monocular depth map prediction, it is barely possible to determine dense ground truth depth images in realistic dynamic outdoor environments. When using LiDAR sensors, for instance, noise is present in the distance measurements, the calibration between sensors cannot be perfect, and the measurements are typically much sparser than the camera images. In this paper, we propose a novel approach to depth map prediction from monocular images that learns in a semi-supervised way. While we use sparse ground-truth depth for supervised learning, we also enforce our deep network to produce photoconsistent dense depth maps in a stereo setup using a direct image alignment loss. In experiments we demonstrate superior performance in depth map prediction from single images compared to the state-of-the-art methods. We present a viewpoint-based approach for the quick fusion of multiple stereo depth maps. Our method selects depth estimates for each pixel that minimize violations of visibility constraints and thus remove errors and inconsistencies from the depth maps to produce a consistent surface. We advocate a two-stage process in which the first stage generates potentially noisy, overlapping depth maps from a set of calibrated images and the second stage fuses these depth maps to obtain an integrated surface with higher accuracy, suppressed noise, and reduced redundancy. We show that by dividing the processing into two stages we are able to achieve a very high throughput because we are able to use a computationally cheap stereo algorithm and because this architecture is amenable to hardware-accelerated (GPU) implementations. A rigorous formulation based on the notion of stability of a depth estimate is presented first. It aims to determine the validity of a depth estimate by rendering multiple depth maps into the reference view as well as rendering the reference depth map into the other views in order to detect occlusions and free- space violations. We also present an approximate alternative formulation that selects and validates only one hypothesis based on confidence. Both formulations enable us to perform video-based reconstruction at up to 25 frames per second. We show results on the multi-view stereo evaluation benchmark datasets and several outdoors video sequences. Extensive quantitative analysis is performed using an accurately surveyed model of a real building as ground truth. Abstract In this paper, we propose a semi-supervised facial landmark detection algorithm (SEMI) based on convolutional neural network (CNN), which can detect facial components and landmarks simultaneously. Unlike previous coarse-to-fine algorithms, our model does not need extra input such as initial landmark prediction. It also solves the occlusion problem of large area by detecting the visible facial components while existing face detectors failed to detect faces. Semi-supervised learning algorithm is also an effective data augmentation method. In our experiment, each image has two types of ground truth, one is bounding-box related (classification and coordinates) and the other is landmark coordinates inside the bounding-box. The supervised data have both two types of ground truth while the semi-supervised data only have the bounding-box. Our model was trained by the merge of two parts of data. Extensive evaluations on Helen, LFPW and 300-W show that our algorithm is able to complete the landmark task and performs better than many state-of-the-art facial landmark detecting algorithms. We present a novel phase-based approach for reconstructing 4D light field from a micro-baseline stereo pair. Our approach takes advantage of the unique property of complex steerable pyramid filters in micro-baseline stereo. We first introduce a Disparity Assisted Phase based Synthesis (DAPS) strategy that can integrate disparity information into the phase term of a reference image to warp it to its close neighbor views. Based on the DAPS, an “analysis by synthesis” approach is proposed to warp from one of the input binocular images to the other, and iteratively optimize the disparity map to minimize the phase differences between the warped one and the ground truth input. Finally, the densely and regularly spaced, high quality light field images can be reconstructed using the proposed DAPS according to the refined disparity map. Our approach also solves the problems of disparity inconsistency and ringing artifact in available phase-based view synthesis methods. Experimental results demonstrate that our approach substantially improves both the quality of disparity map and light field, compared with the state-of-the-art stereo matching and image based rendering approaches.