Scene representation networks, or implicit neural representations (INR) have seen a range of success in numerous image and video applications. However, being universal function fitters, they fit all variations in videos without any selectivity. This is particularly a problem for tasks such as remote plethysmography, the extraction of heart rate information from face videos. As a result of low native signal to noise ratio, previous signal processing techniques suffer from poor performance, while previous learning-based methods have improved performance but suffer from hallucinations that mitigate generalizability. Directly applying prior INRs cannot remedy this signal strength deficit, since they fit to both the signal as well as interfering factors. In this work, we introduce an INR framework that increases this plethysmograph signal strength. Specifically, we leverage architectures to have selective representation capabilities. We are able to decompose the face video into a blood plethysmograph component, and a face appearance component. By inferring the plethysmograph signal from this blood component, we show state-of-the-art performance on out-of-distribution samples without sacrificing performance for in-distribution samples. We implement our framework on a custom-built multiresolution hash encoding backbone to enable practical dataset-scale representations through a 50x speed-up over traditional INRs. We also present a dataset of optically challenging out-of-distribution scenes to test generalization to real-world scenarios. Code and data may be found at https://implicitppg.github.io/.
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Within the video, different regions have varying motion complexity, with simple regions containing static or global motion and complex regions containing fast motion or lots of local motion. In recent years, the performance of flow-based Video Frame Interpolation (VFI) algorithms has improved significantly. However, existing training methods train on randomly cropped regions of train data without considering the complexity of the motion. As a result, they cannot handle all regions of the frame that contain varying motion complexity. To solve this problem, we propose a novel VFI approach (IAM-VFI) that can interpolate any motion by considering the motion complexity of all regions in the frame. First, we propose a training data classification method for motion optimization based on each motion complexity. Then, using the proposed data, a flow estimation network generates optimized results for each complexity. Finally, we propose a Motion Complexity Estimation Network (MCENet) to generate a Motion Complexity Map (MCM) that can estimate the motion complexity of each region. Our proposed methods can be easily applied to most flow-based VFI algorithms. Experimental results show that the proposed method can interpolate any motion and significantly improve the performance of existing VFI algorithms.
The spike camera continuously records scene radiance with high-speed, high dynamic range, and low data redundancy properties, as a promising replacement for frame-based high-speed cameras. Previous methods for reconstructing color videos from monochromatic spikes are constrained in capturing full-temporal color information due to their reliance on compensating colors from low-speed RGB frames. Applying a Bayer-pattern color filter array to the spike sensor yields mosaicked chromatic spikes, which complicates noise distribution in high-speed conditions. By validating that the noise of short-term frames follows a zero-mean distribution, we leverage this hypothesis to develop a self-supervised denoising module trained exclusively on real-world data. Although noise is reduced in short-term frames, the long-term accumulation of incident photons is still necessary to construct HDR frames. Therefore, we introduce a progressive warping module to generate pseudo long-term exposure frames. This approach effectively mitigates motion blur artifacts in high-speed conditions. Integrating these modules forms a real-data-driven reconstruction method for mosaicked chromatic spikes. Extensive experiments conducted on both synthetic and real-world data demonstrate that our approach is effective in reconstructing 2000FPS color HDR videos with significantly reduced noise and motion blur compared to existing methods.
Stochastic Human Motion Prediction (HMP) aims to predict multiple possible future pose sequences from observed ones. Most prior works learn motion distributions through encoding-decoding in latent space, which does not preserve motion’s spatial-temporal structure. While effective, these methods often require complex, multi-stage training and yield predictions that are inconsistent with the provided history and can be physically unrealistic. To address these issues, we propose CoMusion, a single-stage, end-to-end diffusion-based stochastic HMP framework. CoMusion is inspired from the insight that a smooth future pose initialization improves prediction performance, a strategy not previously utilized in stochastic models but evidenced in deterministic works. To generate such initialization, CoMusion's motion predictor starts with a Transformer-based network for initial reconstruction of corrupted motion. Then, a graph convolutional network (GCN) is employed to refine the prediction considering past observations in the discrete cosine transformation (DCT) space. Our method, facilitated by the Transformer-GCN module design and a proposed variance scheduler, excels in predicting accurate, realistic, and consistent motion, while maintaining an appropriate level of diversity. Experimental results on benchmark datasets demonstrate that CoMusion surpasses prior methods in both accuracy and fidelity, achieving at least a 35% relative improvement in fidelity metrics, while demonstrating superior robustness. Our method, facilitated by the Transformer-GCN module design and a proposed variance scheduler, excels in predicting accurate, realistic, and consistent motions, while maintaining an appropriate level of diversity. Experimental results on benchmark datasets demonstrate that CoMusion surpasses prior methods in both accuracy and fidelity, achieving at least a 35% relative improvement in fidelity metrics, while demonstrating superior robustness.
3D keypoint detection plays a pivotal role in 3D shape analysis. The majority of prevalent methods depend on producing a shared heatmap. This approach necessitates subsequent post-processing techniques such as clustering or non-maximum suppression (NMS) to pinpoint keypoints within high-confidence regions, resulting in performance inefficiencies. To address this issue, we introduce KeypointDETR, an end-to-end 3D keypoint detection framework. KeypointDETR is predominantly trained with a bipartite matching loss, which compels the network to forecast sets of heatmaps and probabilities for potential keypoints. Each heatmap highlights one keypoint's location, and the associated probability indicates not only the presence of that specific keypoint but also its semantic consistency. Together with the bipartite matching loss, we utilize a transformer-based network architecture, which incorporates both point-wise and query-wise self-attention within the encoder and decoder, respectively. The point-wise encoder leverages self-attention mechanisms on a dynamic graph derived from the local feature space of each point, resulting in the generation of heatmap features. As a key part of our framework, the query-wise decoder not only facilitates inter-query information exchange but also captures the underlying connections among keypoints' heatmaps, positions, and semantic attributes via the cross-attention mechanism, enabling the prediction of heatmaps and probabilities. Extensive experiments conducted on the KeypointNet dataset reveal that KeypointDETR outperforms competitive baselines, demonstrating superior performance in keypoint saliency and correspondence estimation tasks.
Machine unlearning has become a pivotal task to erase the influence of data from a trained model. It adheres to recent data regulation standards and enhances the privacy and security of machine learning applications. In this work, we present a new machine unlearning approach Scissorhands. Initially, Scissorhands identifies the most pertinent parameters in the given model relative to the forgetting data via connection sensitivity. By reinitializing the most influential top-k percent of these parameters, a trimmed model for erasing the influence of the forgetting data is obtained. Subsequently, Scissorhands fine-tunes the trimmed model with a gradient projection-based approach, seeking parameters that preserve information on the remaining data while discarding information related to the forgetting data. Our experimental results, conducted across image classification and image generation tasks, demonstrate that Scissorhands, showcases competitive performance when compared to existing methods. Source code is available at https://github.com/AnonymousUser-hi/Scissorhands.
Recent advances in contrastive language-image pretraining (CLIP) have demonstrated strong capabilities in zero-shot classification by aligning visual and textual features at an image level. However, in dense prediction tasks, CLIP often struggles to localize visual features within an image and fails to attain favorable pixel-level segmentation results. In this work, we investigate in CLIP's spatial reasoning mechanism and identify that its failure of dense prediction is caused by a location misalignment issue in the self-attention process. Based on this observation, we propose a training-free adaptation approach for CLIP's semantic segmentation, which only introduces a very simple modification to CLIP but can effectively address the issue of location misalignment. Specifically, we reform the self-attention mechanism with leveraging query-to-query and key-to-key similarity to determine attention scores. Remarkably, this minimal modification to CLIP significantly enhances its capability in dense prediction, improving the original CLIP's 14.1% average zero-shot mIoU over eight semantic segmentation benchmarks to 38.2%, and outperforming the existing SoTA's 33.9% by a large margin.
Recent advances in Neural Fields mostly rely on developing task-specific supervision which often complicates the models. Rather than developing hard-to-combine and specific modules, another approach generally overlooked is to directly inject generic priors on the scene representation (also called inductive biases) into the NeRF architecture. Based on this idea, we propose the RING-NeRF architecture which includes two inductive biases : a continuous multi-scale representation of the scene and an invariance of the decoder's latent space over spatial and scale domains. We also design a single reconstruction process that takes advantage of those inductive biases and experimentally demonstrates on-par performances in terms of quality with dedicated architecture on multiple tasks (anti-aliasing, few view reconstruction, SDF reconstruction without scene-specific initialization) while being more efficient. Moreover, RING-NeRF has the distinctive ability to dynamically increase the resolution of the model, opening the way to adaptive reconstruction.
Real-world aerial scene understanding is limited by a lack of datasets that contain densely annotated images curated under a diverse set of conditions. Due to inherent challenges in obtaining such images in controlled real-world settings, we present SkyScenes, a synthetic dataset of densely annotated aerial images captured from Unmanned Aerial Vehicle (UAV) perspectives. We carefully curate SkyScenes images from CARLA to comprehensively capture diversity across layouts (urban and rural maps), weather conditions, times of day, pitch angles and altitudes with corresponding semantic, instance and depth annotations. Through our experiments using SkyScenes, we show that (1) models trained on SkyScenes generalize well to different real-world scenarios, (2) augmenting training on real images with SkyScenes data can improve real-world performance, (3) controlled variations in SkyScenes can offer insights into how models respond to changes in viewpoint conditions, and (4) incorporating additional sensor modalities (depth) can improve aerial scene understanding.
Rethinking Fast Adversarial Training: A Splitting Technique To Overcome Catastrophic Overfitting
PDF ↗Catastrophic overfitting (CO) poses a significant challenge to fast adversarial training (FastAT), particularly at large perturbation scales, leading to dramatic reductions in adversarial test accuracy. Our analysis of existing FastAT methods shows that CO is accompanied by abrupt and irregular fluctuations in loss convergence, indicating that a stable training dynamic is key to preventing CO. Therefore, we propose a training model that uses the Douglas-Rachford (DR) splitting technique to ensure a balanced and consistent training progression, effectively counteracting CO. The DR splitting technique, known for its ability to solve complex optimization problems, offering a distinct advantage over classical FastAT methods by providing a smoother loss convergence. This is achieved without resorting to complex regularization or incurring the computational costs associated with double backpropagation, presenting an efficient solution to enhance adversarial robustness. Our comprehensive evaluation conducted across standard datasets, demonstrates that our DR splitting-based model not only improves adversarial robustness but also achieves this with remarkable efficiency compared to various FastAT methods. This efficiency is particularly observed under conditions involving long training schedules and large adversarial perturbations.
Diffusion models achieve remarkable quality in image generation, but at a cost. Iterative denoising requires many time steps to produce high fidelity images. We argue that the denoising process is crucially limited by an accumulation of the reconstruction error due to an initial inaccurate reconstruction of the target data. This leads to lower quality outputs, and slower convergence. To address these issues, we propose compensation sampling to guide the generation towards the target domain. We introduce a compensation term, implemented as a U-Net, which adds negligible computation overhead during training. Our approach is flexible and we demonstrate its application in unconditional generation, face inpainting, and face de-occlusion on benchmark datasets CIFAR-10, CelebA, CelebA-HQ, FFHQ-256, and FSG. Our approach consistently yields state-of-the-art results in terms of image quality, while accelerating the denoising process to converge during training by up to an order of magnitude.
The field of autonomous driving has attracted considerable interest in approaches that directly infer 3D objects in the Bird's Eye View (BEV) from multiple cameras. Some attempts have also explored utilizing 2D detectors from single images to enhance the performance of 3D detection. However, these approaches rely on a two-stage process with separate detectors, where the 2D detection results are utilized only once for token selection or query initialization. In this paper, we present a single model termed SimPB, which Simultaneously detects 2D objects in the Perspective view and 3D objects in the BEV space from multiple cameras. To achieve this, we introduce a hybrid decoder consisting of several multi-view 2D decoder layers and several 3D decoder layers, specifically designed for their respective detection tasks. A Dynamic Query Allocation module and an Adaptive Query Aggregation module are proposed to continuously update and refine the interaction between 2D and 3D results, in a cyclic 3D-2D-3D manner. Additionally, Query-group Attention is utilized to strengthen the interaction among 2D queries within each camera group. In the experiments, we evaluate our method on the nuScenes dataset and demonstrate promising results for both 2D and 3D detection tasks. We will make the code publicly available.
Inspired by the remarkable achievements of Large Language Models (LLMs), Large Vision-Language Models (LVLMs) have likewise experienced significant advancements. However, the increased computational cost and token budget occupancy associated with lengthy visual tokens pose significant challenge to the practical applications. Considering that not all visual tokens are essential to the final response, selectively pruning redundant visual tokens can effectively alleviate this challenge. In this paper, we present a novel Instruction-guided Visual Token Pruning (IVTP) approach for LVLMs, which is designed to strike a better balance between computational efficiency and the performance. Specifically, a Group-wise Token Pruning (GTP) module based on attention rollout is integrated into the grouped transformer layer to achieve intra-group attention aggregation via residual connection, thereby improving the assessment of visual token importance, especially for LVLMs with a frozen visual encoder. We then extend the module to LLM in order to further filter out visual tokens that are pertinent to the current textual instructions, by introducing a semantically related pseudo CLS token to serve as a reference for token pruning. This two-stage token pruning mechanism permits a systematic and efficient reduction in the quantity of visual tokens while preserving essential visual information. We apply the proposed method to the most representative LVLM, i.e. LLaVA-1.5. Experimental results demonstrate that when the number of visual tokens is reduced by 88.9%, the computational complexity is decreased by over 46%, with only an average 1.0% accuracy drop across 12 benchmarks, and remarkably surpasses the state-of-the-art token pruning methods. It is worth noting that the proposed method can also work without requiring retraining, thus enabling it to serve as a plug-in across a broader range of LVLMs. Code and trained weights will be available.
Building calibrated object detectors is a crucial challenge to address for their reliable usage in safety-critical applications. Recent approaches towards this involve (1) designing new loss functions to obtain calibrated detectors by training them from scratch, and (2) post-hoc Temperature Scaling (TS) that learns to scale the likelihood of a trained detector to output calibrated predictions. These approaches are then evaluated based on a combination of Detection Expected Calibration Error (D-ECE) and Average Precision. In this work, via extensive analysis and insights, we highlight that these recent evaluation frameworks, evaluation metrics, and the use of TS have significant drawbacks leading to incorrect conclusions. As a remedy, we propose a principled evaluation framework to jointly measure calibration and accuracy of object detectors. We also tailor efficient and easy-to-use post-hoc calibration approaches, Platt Scaling and Isotonic Regression, specifically to object detection. As opposed to the common notion, our experiments show that, once designed and evaluated properly, post-hoc calibrators, which are extremely cheap to build and use, are much more powerful and effective than the recent train time calibration methods. To illustrate, D-DETR with our post-hoc Isotonic Regression calibrator outperforms the state-of-the-art Cal-DETR by more than 7 D-ECE on the COCO dataset. We also provide improved versions of Localization-aware ECE and show the efficacy of our method on these metrics as well. Code will be made public.
Single Image Super-Resolution (SISR) plays a vital role in various applications, driven by advancements in Deep Neural Networks (DNNs). However, increasing model complexity raises computational costs, necessitating efficient solutions. Existing patch-based approaches aiming at efficient SR encounter challenges in adapting to varying pixel difficulties and suffer from decreased efficiency with larger patches. To address these limitations, we propose Pixel-level Classifier for Single Image Super-Resolution (PCSR), a novel pixel-level distribution method for efficient SISR. Our approach optimizes computational resource allocation at the pixel level, achieving better efficiency compared to patch-based methods, and also provides user tunability without re-training and mitigates artifacts through post-processing techniques. Experimental results demonstrate the effectiveness of PCSR across diverse SISR models and benchmarks, surpassing existing approaches in terms of the PSNR-FLOPs trade-off.
Many computer vision and machine learning problems are modelled as learning tasks on graphs, where graph neural networks (GNNs) have emerged as a dominant tool for learning representations of graph-structured data. A key feature of GNNs is their use of graph structures as input, enabling them to exploit the graphs' inherent topological properties—known as the topology awareness of GNNs. Despite the empirical successes of GNNs, the influence of topology awareness on generalization performance remains unexplored, particularly for node-level tasks that diverge from the assumption of data being independent and identically distributed (I.I.D.). The precise definition and characterization of the topology awareness of GNNs, especially concerning different topological features, are still unclear. This paper introduces a comprehensive framework to characterize the topology awareness of GNNs across any topological feature. Using this framework, we investigate the effects of topology awareness on GNN generalization performance. Contrary to the prevailing belief that enhancing the topology awareness of GNNs is always advantageous, our analysis reveals a critical insight: improving the topology awareness of GNNs may inadvertently lead to unfair generalization across structural groups, which might not be desired in some scenarios. Additionally, we conduct a case study using the intrinsic graph metric, the shortest-path distance, on various benchmark datasets. The empirical results of this case study confirm our theoretical insights. Moreover, we demonstrate the practical applicability of our framework by using it to tackle the cold start problem in graph active learning.
Digitising the 3D world into a clean, CAD model-based representation has important applications for augmented reality and robotics. Current state-of-the-art methods are computationally intensive as they individually encode each detected object and optimise CAD alignments in a second stage. In this work, we propose FastCAD, a real-time method that simultaneously retrieves and aligns CAD models for all objects in a given scene. In contrast to previous works, we directly predict alignment parameters and shape embeddings. We achieve high-quality shape retrievals by learning CAD embeddings in a contrastive learning framework and distilling those into FastCAD. Our single-stage method accelerates the inference time by a factor of 50 compared to other methods operating on RGB-D scans while outperforming them on the challenging Scan2CAD alignment benchmark. Further, our approach collaborates seamlessly with online 3D reconstruction techniques. This enables the real-time generation of precise CAD model-based reconstructions from videos at 10 FPS. Doing so, we significantly improve the Scan2CAD alignment accuracy in the video setting from 43.0% to 48.2% and the reconstruction accuracy from 22.9% to 29.6%.
High dynamic range imaging records natural scenes with closer to actual luminance distributions, at the cost of increased storage requirements and display demands. Consequently, HDR image compression for perceptually optimal storage and display is crucial, yet it remains inadequately addressed. In this work, we take steps towards this goal. Specifically, we learn to compress HDR images into two bitstreams for storage, one of which is used to generate low dynamic range (LDR) images for display purposes conditioned on the maximum luminance of the scene, while the other serves as side information to aid HDR image reconstruction from the generated LDR image. To measure the perceptual quality of the displayable LDR image, we employ the normalized Laplacian pyramid distance (NLPD), a perceptually quality metric that supports the use of the input HDR image as reference. To measure the perceptual quality of the reconstructed HDR image, we employ a newly proposed HDR quality metric based on a simple inverse display model that enables high-fidelity dynamic range expansion at all luminance levels. Comprehensive qualitative and quantitative comparisons on various HDR scenes demonstrate the perceptual optimality of our learned HDR image compression system for both displayable LDR images and reconstructed HDR images at all bit rates.
It is challenging to reconstruct 3D point clouds in unseen classes from single 2D images. Instead of object-centered coordinate system, current methods generalized global priors learned in seen classes to reconstruct 3D shapes from unseen classes in viewer-centered coordinate system. However, the reconstruction accuracy and interpretability are still eager to get improved. To resolve this issue, we introduce to learn local pattern modularization for reconstructing 3D shapes in unseen classes, which achieves both good generalization ability and high reconstruction accuracy. Our insight is to learn a local prior which is class-agnostic and easy to generalize in object-centered coordinate system. Specifically, the local prior is learned via a process of learning and customizing local pattern modularization in seen classes. During this process, we first learn a set of patterns in local regions, which is the basis in the object-centered coordinate system to represent an arbitrary region on shapes across different classes. Then, we modularize each region on an initially reconstructed shape using the learned local patterns. Based on that, we customize the local pattern modularization using the input image by refining the reconstruction with more details. Our method enables to reconstruct high fidelity point clouds from unseen classes in object-centered coordinate system without requiring a large number of patterns or any additional information, such as segmentation supervision or camera poses. Our experimental results under widely used benchmarks show that our method achieves the state-of-the-art reconstruction accuracy for shapes from unseen classes.
This paper develops small vision language models to understand visual art, which, given an art work, aims to identify its emotion category and explain this prediction with natural language. While small models are computationally efficient, their capacity is much limited compared with large models. To break this trade-off, this paper builds a small emotional vision language model (SEVLM) by emotion modeling and input-output feature alignment. On the one hand, based on valence-arousal-dominance (VAD) knowledge annotated by psychology experts, we introduce and fuse emotional features derived through VAD dictionary and a VAD head to align VAD vectors of predicted emotion explanation and the ground truth. This allows the vision language model to better understand and generate emotional texts, compared with using traditional text embeddings alone. On the other hand, we design a contrastive head to pull close embeddings of the image, its emotion class, and explanation, which aligns model outputs and inputs. On two public affective explanation datasets, we show that the proposed techniques consistently improve the visual art understanding performance of baseline SEVLMs. Importantly, the proposed model can be trained and evaluated on a single RTX 2080 Ti while exhibiting very strong performance: it not only outperforms the state-of-the-art small models but is also competitive compared with LLaVA 7B after fine-tuning and GPT4(V). Code will be made publicly available.