228 research outputs found
E-RAFT: Dense Optical Flow from Event Cameras
We propose to incorporate feature correlation and sequential processing into dense optical flow estimation from event cameras. Modern frame-based optical flow methods heavily rely on matching costs computed from feature correlation. In contrast, there exists no optical flow method for event cameras that explicitly computes matching costs. Instead, learning-based approaches using events usually resort to the U-Net architecture to estimate optical flow sparsely. Our key finding is that the introduction of correlation features significantly improves results compared to previous methods that solely rely on convolution layers. Compared to the state-of-the-art, our proposed approach computes dense optical flow and reduces the end-point error by 23% on MVSEC. Furthermore, we show that all existing optical flow methods developed so far for event cameras have been evaluated on datasets with very small displacement fields with maximum flow magnitude of 10 pixels. Based on this observation, we introduce a new real-world dataset that exhibits displacement fields with magnitudes up to 210 pixels and 3 times higher camera resolution. Our proposed approach reduces the end-point error on this dataset by 66%
Bridging the Gap Between Events and Frames Through Unsupervised Domain Adaptation
Reliable perception during fast motion maneuvers or in high dynamic range environments is crucial for robotic systems. Since event cameras are robust to these challenging conditions, they have great potential to increase the reliability of robot vision. However, event-based vision has been held back by the shortage of labeled datasets due to the novelty of event cameras. To overcome this drawback, we propose a task transfer method to train models directly with labeled images and unlabeled event data. Compared to previous approaches, (i) our method transfers from single images to events instead of high frame rate videos, and (ii) does not rely on paired sensor data. To achieve this, we leverage the generative event model to split event features into content and motion features. This split enables efficient matching between latent spaces for events and images, which is crucial for successful task transfer. Thus, our approach unlocks the vast amount of existing image datasets for the training of event-based neural networks. Our task transfer method consistently outperforms methods targeting Unsupervised Domain Adaptation for object detection by 0.26 mAP (increase by 93%) and classification by 2.7% accuracy
DSEC: A Stereo Event Camera Dataset for Driving Scenarios
Once an academic venture, autonomous driving has received unparalleled
corporate funding in the last decade. Still, the operating conditions of
current autonomous cars are mostly restricted to ideal scenarios. This means
that driving in challenging illumination conditions such as night, sunrise, and
sunset remains an open problem. In these cases, standard cameras are being
pushed to their limits in terms of low light and high dynamic range
performance. To address these challenges, we propose, DSEC, a new dataset that
contains such demanding illumination conditions and provides a rich set of
sensory data. DSEC offers data from a wide-baseline stereo setup of two color
frame cameras and two high-resolution monochrome event cameras. In addition, we
collect lidar data and RTK GPS measurements, both hardware synchronized with
all camera data. One of the distinctive features of this dataset is the
inclusion of high-resolution event cameras. Event cameras have received
increasing attention for their high temporal resolution and high dynamic range
performance. However, due to their novelty, event camera datasets in driving
scenarios are rare. This work presents the first high-resolution, large-scale
stereo dataset with event cameras. The dataset contains 53 sequences collected
by driving in a variety of illumination conditions and provides ground truth
disparity for the development and evaluation of event-based stereo algorithms.Comment: IEEE Robotics and Automation Letter
From Chaos Comes Order: Ordering Event Representations for Object Recognition and Detection
Today, state-of-the-art deep neural networks that process events first
convert them into dense, grid-like input representations before using an
off-the-shelf network. However, selecting the appropriate representation for
the task traditionally requires training a neural network for each
representation and selecting the best one based on the validation score, which
is very time-consuming. This work eliminates this bottleneck by selecting
representations based on the Gromov-Wasserstein Discrepancy (GWD) between raw
events and their representation. It is about 200 times faster to compute than
training a neural network and preserves the task performance ranking of event
representations across multiple representations, network backbones, datasets,
and tasks. Thus finding representations with high task scores is equivalent to
finding representations with a low GWD. We use this insight to, for the first
time, perform a hyperparameter search on a large family of event
representations, revealing new and powerful representations that exceed the
state-of-the-art. Our optimized representations outperform existing
representations by 1.7 mAP on the 1 Mpx dataset and 0.3 mAP on the Gen1
dataset, two established object detection benchmarks, and reach a 3.8% higher
classification score on the mini N-ImageNet benchmark. Moreover, we outperform
state-of-the-art by 2.1 mAP on Gen1 and state-of-the-art feed-forward methods
by 6.0 mAP on the 1 Mpx datasets. This work opens a new unexplored field of
explicit representation optimization for event-based learning.Comment: 15 pages, 11 figures, 2 tables, ICCV 2023 Camera Ready pape
From Chaos Comes Order: Ordering Event Representations for Object Recognition and Detection
Today, state-of-the-art deep neural networks that process events first convert them into dense, grid-like input representations before using an off-the-shelf network. However, selecting the appropriate representation for the task traditionally requires training a neural network for each representation and selecting the best one based on the validation score, which is very time-consuming. This work eliminates this bottleneck by selecting representations based on the Gromov-Wasserstein Discrepancy (GWD) between raw events and their representation. It is about 200 times faster to compute than training a neural network and preserves the task performance ranking of event representations across multiple representations, network backbones, datasets, and tasks. Thus finding representations with high task scores is equivalent to finding representations with a low GWD. We use this insight to, for the first time, perform a hyperparameter search on a large family of event representations, revealing new and powerful representations that exceed the state-of-the-art. Our optimized representations outperform existing representations by 1.7 mAP on the 1 Mpx dataset and 0.3 mAP on the Gen1 dataset, two established object detection benchmarks, and reach a 3.8% higher classification score on the mini N-ImageNet benchmark. Moreover, we outperform state-of-the-art by 2.1 mAP on Gen1 and state-of-the-art feed-forward methods by 6.0 mAP on the 1 Mpx datasets. This work opens a new unexplored field of explicit representation optimization for event-based learning
E-RAFT: Dense Optical Flow from Event Cameras
We propose to incorporate feature correlation and sequential processing into dense optical flow estimation from event cameras. Modern frame-based optical flow methods heavily rely on matching costs computed from feature correlation. In contrast, there exists no optical flow method for event cameras that explicitly computes matching costs. Instead, learning-based approaches using events usually resort to the U-Net architecture to estimate optical flow sparsely. Our key finding is that the introduction of correlation features significantly improves results compared to previous methods that solely rely on convolution layers. Compared to the state-of-the-art, our proposed approach computes dense optical flow and reduces the end-point error by 23% on MVSEC. Furthermore, we show that all existing optical flow methods developed so far for event cameras have been evaluated on datasets with very small displacement fields with maximum flow magnitude of 10 pixels. Based on this observation, we introduce a new real-world dataset that exhibits displacement fields with magnitudes up to 210 pixels and 3 times higher camera resolution. Our proposed approach reduces the end-point error on this dataset by 66%
End-to-End Learning of Representations for Asynchronous Event-Based Data
Event cameras are vision sensors that record asynchronous streams of
per-pixel brightness changes, referred to as "events". They have appealing
advantages over frame-based cameras for computer vision, including high
temporal resolution, high dynamic range, and no motion blur. Due to the sparse,
non-uniform spatiotemporal layout of the event signal, pattern recognition
algorithms typically aggregate events into a grid-based representation and
subsequently process it by a standard vision pipeline, e.g., Convolutional
Neural Network (CNN). In this work, we introduce a general framework to convert
event streams into grid-based representations through a sequence of
differentiable operations. Our framework comes with two main advantages: (i)
allows learning the input event representation together with the task dedicated
network in an end to end manner, and (ii) lays out a taxonomy that unifies the
majority of extant event representations in the literature and identifies novel
ones. Empirically, we show that our approach to learning the event
representation end-to-end yields an improvement of approximately 12% on optical
flow estimation and object recognition over state-of-the-art methods.Comment: To appear at ICCV 201
Video to Events: Recycling Video Datasets for Event Cameras
Event cameras are novel sensors that output brightness changes in the form of a stream of asynchronous "events" instead of intensity frames. They offer significant advantages with respect to conventional cameras: high dynamic range (HDR), high temporal resolution, and no motion blur. Recently, novel learning approaches operating on event data have achieved impressive results. Yet, these methods require a large amount of event data for training, which is hardly available due the novelty of event sensors in computer vision research. In this paper, we present a method that addresses these needs by converting any existing video dataset recorded with conventional cameras to synthetic event data. This unlocks the use of a virtually unlimited number of existing video datasets for training networks designed for real event data. We evaluate our method on two relevant vision tasks, i.e., object recognition and semantic segmentation, and show that models trained on synthetic events have several benefits: (i) they generalize well to real event data, even in scenarios where standard-camera images are blurry or overexposed, by inheriting the outstanding properties of event cameras; (ii) they can be used for fine-tuning on real data to improve over state-of-the-art for both classification and semantic segmentation
Pushing the Limits of Asynchronous Graph-based Object Detection with Event Cameras
State-of-the-art machine-learning methods for event cameras treat events as
dense representations and process them with conventional deep neural networks.
Thus, they fail to maintain the sparsity and asynchronous nature of event data,
thereby imposing significant computation and latency constraints on downstream
systems. A recent line of work tackles this issue by modeling events as
spatiotemporally evolving graphs that can be efficiently and asynchronously
processed using graph neural networks. These works showed impressive
computation reductions, yet their accuracy is still limited by the small scale
and shallow depth of their network, both of which are required to reduce
computation. In this work, we break this glass ceiling by introducing several
architecture choices which allow us to scale the depth and complexity of such
models while maintaining low computation. On object detection tasks, our
smallest model shows up to 3.7 times lower computation, while outperforming
state-of-the-art asynchronous methods by 7.4 mAP. Even when scaling to larger
model sizes, we are 13% more efficient than state-of-the-art while
outperforming it by 11.5 mAP. As a result, our method runs 3.7 times faster
than a dense graph neural network, taking only 8.4 ms per forward pass. This
opens the door to efficient, and accurate object detection in edge-case
scenarios
AEGNN: Asynchronous Event-based Graph Neural Networks
The best performing learning algorithms devised for event cameras work by first converting events into dense representations that are then processed using standard CNNs. However, these steps discard both the sparsity and high temporal resolution of events, leading to high computational burden and latency. For this reason, recent works have adopted Graph Neural Networks (GNNs), which process events as “static” spatio-temporal graphs, which are inherently “sparse”. We take this trend one step further by introducing Asynchronous, Event-based Graph Neural Networks (AEGNNs), a novel event-processing paradigm that generalizes standard GNNs to process events as “evolving” spatio-temporal graphs. AEGNNs follow efficient update rules that restrict recomputation of network activations only to the nodes affected by each new event, thereby significantly reducing both computation and latency for event-by-event processing. AEGNNs are easily trained on synchronous inputs and can be converted to efficient, “asynchronous” networks at test time. We thoroughly validate our method on object classification and detection tasks, where we show an up to a 200-fold reduction in computational complexity (FLOPs), with similar or even better performance than state-of-the-art asynchronous methods. This reduction in computation directly translates to an 8-fold reduction in computational latency when compared to standard GNNs, which opens the door to low-latency event-based processing
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