CVPR 2024 论文列表

Epistemic uncertainty quantification (UQ) identifies where models lack knowledge. Traditional UQ methods often based on Bayesian neural networks are not suitable for pre-trained non-Bayesian models. Our study addresses quantifying epistemic uncertainty for any pre-trained model which does not need the original training data or model modifications and can ensure broad applicability regardless of network architectures or training techniques. Specifically we propose a gradient-based approach to assess epistemic uncertainty analyzing the gradients of outputs relative to model parameters and thereby indicating necessary model adjustments to accurately represent the inputs. We first explore theoretical guarantees of gradient-based methods for epistemic UQ questioning the view that this uncertainty is only calculable through differences between multiple models. We further improve gradient-driven UQ by using class-specific weights for integrating gradients and emphasizing distinct contributions from neural network layers. Additionally we enhance UQ accuracy by combining gradient and perturbation methods to refine the gradients. We evaluate our approach on out-of-distribution detection uncertainty calibration and active learning demonstrating its superiority over current state-of-the-art UQ methods for pre-trained models.

Generating multiview images from a single view facilitates the rapid generation of a 3D mesh conditioned on a single image. Recent methods that introduce 3D global representation into diffusion models have shown the potential to generate consistent multiviews but they have reduced generation speed and face challenges in maintaining generalizability and quality. To address this issue we propose EpiDiff a localized interactive multiview diffusion model. At the core of the proposed approach is to insert a lightweight epipolar attention block into the frozen diffusion model leveraging epipolar constraints to enable cross-view interaction among feature maps of neighboring views. The newly initialized 3D modeling module preserves the original feature distribution of the diffusion model exhibiting compatibility with a variety of base diffusion models. Experiments show that EpiDiff generates 16 multiview images in just 12 seconds and it surpasses previous methods in quality evaluation metrics including PSNR SSIM and LPIPS. Additionally EpiDiff can generate a more diverse distribution of views improving the reconstruction quality from generated multiviews. Please see the project page at https://huanngzh.github.io/EpiDiff/.

Recent advancements in the study of Neural Radiance Fields (NeRF) for dynamic scenes often involve explicit modeling of scene dynamics. However this approach faces challenges in modeling scene dynamics in urban environments where moving objects of various categories and scales are present. In such settings it becomes crucial to effectively eliminate moving objects to accurately reconstruct static backgrounds. Our research introduces an innovative method termed here as Entity-NeRF which combines the strengths of knowledge-based and statistical strategies. This approach utilizes entity-wise statistics leveraging entity segmentation and stationary entity classification through thing/stuff segmentation. To assess our methodology we created an urban scene dataset masked with moving objects. Our comprehensive experiments demonstrate that Entity-NeRF notably outperforms existing techniques in removing moving objects and reconstructing static urban backgrounds both quantitatively and qualitatively.

Generalizable NeRF can directly synthesize novel views across new scenes eliminating the need for scene-specific retraining in vanilla NeRF. A critical enabling factor in these approaches is the extraction of a generalizable 3D representation by aggregating source-view features. In this paper we propose an Entangled View-Epipolar Information Aggregation method dubbed EVE-NeRF. Different from existing methods that consider cross-view and along-epipolar information independently EVE-NeRF conducts the view-epipolar feature aggregation in an entangled manner by injecting the scene-invariant appearance continuity and geometry consistency priors to the aggregation process. Our approach effectively mitigates the potential lack of inherent geometric and appearance constraint resulting from one-dimensional interactions thus further boosting the 3D representation generalizablity. EVE-NeRF attains state-of-the-art performance across various evaluation scenarios. Extensive experiments demonstate that compared to prevailing single-dimensional aggregation the entangled network excels in the accuracy of 3D scene geometry and appearance reconstruction. Our code is publicly available at https://github.com/tatakai1/EVENeRF.

With the advent of ensemble-based attacks the transferability of generated adversarial examples is elevated by a noticeable margin despite many methods only employing superficial integration yet ignoring the diversity between ensemble models. However most of them compromise the latent value of the diversity between generated perturbation from distinct models which we argue is also able to increase the adversarial transferability especially heterogeneous attacks. To address the issues we propose a novel method of Stochastic Mini-batch black-box attack with Ensemble Reweighing using reinforcement learning (SMER) to produce highly transferable adversarial examples. We emphasize the diversity between surrogate models achieving individual perturbation iteratively. In order to customize the individual effect between surrogates ensemble reweighing is introduced to refine ensemble weights by maximizing attack loss based on reinforcement learning which functions on the ultimate transferability elevation. Extensive experiments demonstrate our superiority to recent ensemble attacks with a significant margin across different black-box attack scenarios especially on heterogeneous conditions.

In this work we present a novel perspective on detecting out-of-distribution (OOD) samples and propose an algorithm for sample-aware model selection to enhance the effectiveness of OOD detection. Our algorithm determines for each test input which pre-trained models in the model zoo are capable of identifying the test input as an OOD sample. If no such models exist in the model zoo the test input is classified as an in-distribution (ID) sample. We theoretically demonstrate that our method maintains the true positive rate of ID samples and accurately identifies OOD samples with high probability when there are a sufficient number of diverse pre-trained models in the model zoo. Extensive experiments were conducted to validate our method demonstrating that it leverages the complementarity among single-model detectors to consistently improve the effectiveness of OOD sample identification. Compared to base-line methods our approach improved the relative performance by 65.40% and 37.25% on the CIFAR10 and ImageNet benchmarks respectively.

Recently the advent of Large Visual-Language Models (LVLMs) has received increasing attention across various domains particularly in the field of visual document understanding (VDU). Different from conventional vision-language tasks VDU is specifically concerned with text-rich scenarios containing abundant document elements. Nevertheless the importance of fine-grained features remains largely unexplored within the community of LVLMs leading to suboptimal performance in text-rich scenarios. In this paper we abbreviate it as the fine-grained feature collapse issue. With the aim of filling this gap we propose a contrastive learning framework termed Document Object COntrastive learning (DoCo) specifically tailored for the downstream tasks of VDU. DoCo leverages an auxiliary multimodal encoder to obtain the features of document objects and align them to the visual features generated by the vision encoder of LVLM which enhances visual representation in text-rich scenarios. It can represent that the contrastive learning between the visual holistic representations and the multimodal fine-grained features of document objects can assist the vision encoder in acquiring more effective visual cues thereby enhancing the comprehension of text-rich documents in LVLMs. We also demonstrate that the proposed DoCo serves as a plug-and-play pre-training method which can be employed in the pre-training of various LVLMs without inducing any increase in computational complexity during the inference process. Extensive experimental results on multiple benchmarks of VDU reveal that LVLMs equipped with our proposed DoCo can achieve superior performance and mitigate the gap between VDU and generic vision-language tasks.

Continual learning (CL) aims to empower models to learn new tasks without forgetting previously acquired knowledge. Most prior works concentrate on the techniques of architectures replay data regularization etc. However the category name of each class is largely neglected. Existing methods commonly utilize the one-hot labels and randomly initialize the classifier head. We argue that the scarce semantic information conveyed by the one-hot labels hampers the effective knowledge transfer across tasks. In this paper we revisit the role of the classifier head within the CL paradigm and replace the classifier with semantic knowledge from pretrained language models (PLMs). Specifically we use PLMs to generate semantic targets for each class which are frozen and serve as supervision signals during training. Such targets fully consider the semantic correlation between all classes across tasks. Empirical studies show that our approach mitigates forgetting by alleviating representation drifting and facilitating knowledge transfer across tasks. The proposed method is simple to implement and can seamlessly be plugged into existing methods with negligible adjustments. Extensive experiments based on eleven mainstream baselines demonstrate the effectiveness and generalizability of our approach to various protocols. For example under the class-incremental learning setting on ImageNet-100 our method significantly improves the Top-1 accuracy by 3.2% to 6.1% while reducing the forgetting rate by 2.6% to 13.1%.

Existing quality enhancement methods for compressed images focus on aligning the enhancement domain with the raw domain to yield realistic images. However these methods exhibit a pervasive enhancement bias towards the compression domain inadvertently regarding it as more realistic than the raw domain. This bias makes enhanced images closely resemble their compressed counterparts thus degrading their perceptual quality. In this paper we propose a simple yet effective method to mitigate this bias and enhance the quality of compressed images. Our method employs a conditional discriminator with the compressed image as a key condition and then incorporates a domain-divergence regularization to actively distance the enhancement domain from the compression domain. Through this dual strategy our method enables the discrimination against the compression domain and brings the enhancement domain closer to the raw domain. Comprehensive quality evaluations confirm the superiority of our method over other state-of-the-art methods without incurring inference overheads.

Post-training quantization (PTQ) converts a pre-trained full-precision (FP) model into a quantized model in a training-free manner. Determining suitable quantization parameters such as scaling factors and weight rounding is the primary strategy for mitigating the impact of quantization noise (calibration) and restoring the performance of the quantized models. However the existing activation calibration methods have never considered information degradation between pre- (FP) and post-quantized activations. In this study we introduce a well-defined distributional metric from information theory mutual information into PTQ calibration. We aim to calibrate the quantized activations by maximizing the mutual information between the pre- and post-quantized activations. To realize this goal we establish a contrastive learning (CL) framework for the PTQ calibration where the quantization parameters are optimized through a self-supervised proxy task. Specifically by leveraging CL during the PTQ process we can benefit from pulling the positive pairs of quantized and FP activations collected from the same input samples while pushing negative pairs from different samples. Thanks to the ingeniously designed critic function we avoid the unwanted but often-encountered collision solution in CL especially in calibration scenarios where the amount of calibration data is limited. Additionally we provide a theoretical guarantee that minimizing our designed loss is equivalent to maximizing the desired mutual information. Consequently the quantized activations retain more information which ultimately enhances the performance of the quantized network. Experimental results show that our method can effectively serve as an add-on module to existing SoTA PTQ methods.

One primary topic of multimodal learning is to jointly incorporate heterogeneous information from different modalities. However most models often suffer from unsatisfactory multimodal cooperation which cannot jointly utilize all modalities well. Some methods are proposed to identify and enhance the worse learnt modality but they are often hard to provide the fine-grained observation of multimodal cooperation at sample-level with theoretical support. Hence it is essential to reasonably observe and improve the fine-grained cooperation between modalities especially when facing realistic scenarios where the modality discrepancy could vary across different samples. To this end we introduce a sample-level modality valuation metric to evaluate the contribution of each modality for each sample. Via modality valuation we observe that modality discrepancy indeed could be different at sample-level beyond the global contribution discrepancy at dataset-level. We further analyze this issue and improve cooperation between modalities at sample-level by enhancing the discriminative ability of low-contributing modalities in a targeted manner. Overall our methods reasonably observe the fine-grained uni-modal contribution and achieve considerable improvement. The source code and dataset are available at https://github.com/GeWu-Lab/Valuate-and-Enhance-Multimodal-Cooperation.

In the image classification task deep neural networks frequently rely on bias attributes that are spuriously correlated with a target class in the presence of dataset bias resulting in degraded performance when applied to data without bias attributes. The task of debiasing aims to compel classifiers to learn intrinsic attributes that inherently define a target class rather than focusing on bias attributes. While recent approaches mainly focus on emphasizing the learning of data samples without bias attributes (i.e. bias-conflicting samples) compared to samples with bias attributes (i.e. bias-aligned samples) they fall short of directly guiding models where to focus for learning intrinsic features. To address this limitation this paper proposes a method that provides the model with explicit spatial guidance that indicates the region of intrinsic features. We first identify the intrinsic features by investigating the class-discerning common features between a bias-aligned (BA) sample and a bias-conflicting (BC) sample (i.e. bias-contrastive pair). Next we enhance the intrinsic features in the BA sample that are relatively under-exploited for prediction compared to the BC sample. To construct the bias-contrastive pair without using bias information we introduce a bias-negative score that distinguishes BC samples from BA samples employing a biased model. The experiments demonstrate that our method achieves state-of-the-art performance on synthetic and real-world datasets with various levels of bias severity.

Multi-camera-based 3D object detection has made notable progress in the past several years. However we observe that there are cases (e.g. faraway regions) in which popular 2D object detectors are more reliable than state-of-the-art 3D detectors. In this paper to improve the performance of query-based 3D object detectors we present a novel query generating approach termed QAF2D which infers 3D query anchors from 2D detection results. A 2D bounding box of an object in an image is lifted to a set of 3D anchors by associating each sampled point within the box with depth yaw angle and size candidates. Then the validity of each 3D anchor is verified by comparing its projection in the image with its corresponding 2D box and only valid anchors are kept and used to construct queries. The class information of the 2D bounding box associated with each query is also utilized to match the predicted boxes with ground truth for the set-based loss. The image feature extraction backbone is shared between the 3D detector and 2D detector by adding a small number of prompt parameters. We integrate QAF2D into three popular query-based 3D object detectors and carry out comprehensive evaluations on the nuScenes dataset. The largest improvement that QAF2D can bring about on the nuScenes validation subset is 2.3% NDS and 2.7% mAP. Code is available at https://github.com/max-vision/QAF2D.

Leveraging multi-view diffusion models as priors for 3D optimization have alleviated the problem of 3D consistency e.g. the Janus face problem or the content drift problem in zero-shot text-to-3D models. However the 3D geometric fidelity of the output remains an unresolved issue; albeit the rendered 2D views are realistic the underlying geometry may contain errors such as unreasonable concavities. In this work we propose CorrespondentDream an effective method to leverage annotation-free cross-view correspondences yielded from the diffusion U-Net to provide additional 3D prior to the NeRF optimization process. We find that these correspondences are strongly consistent with human perception and by adopting it in our loss design we are able to produce NeRF models with geometries that are more coherent with common sense e.g. more smoothed object surface yielding higher 3D fidelity. We demonstrate the efficacy of our approach through various comparative qualitative results and a solid user study.

Extending large image-text pre-trained models (e.g. CLIP) for video understanding has made significant advancements. To enable the capability of CLIP to perceive dynamic information in videos existing works are dedicated to equipping the visual encoder with various temporal modules. However these methods exhibit "asymmetry" between the visual and textual sides with neither temporal descriptions in input texts nor temporal modules in text encoder. This limitation hinders the potential of language supervision emphasized in CLIP and restricts the learning of temporal features as the text encoder has demonstrated limited proficiency in motion understanding. To address this issue we propose leveraging "MoTion-Enhanced Descriptions" (MoTED) to facilitate the extraction of distinctive temporal features in videos. Specifically we first generate discriminative motion-related descriptions via querying GPT-4 to compare easy-confusing action categories. Then we incorporate both the visual and textual encoders with additional perception modules to process the video frames and generated descriptions respectively. Finally we adopt a contrastive loss to align the visual and textual motion features. Extensive experiments on five benchmarks show that MoTED surpasses state-of-the-art methods with convincing gaps laying a solid foundation for empowering CLIP with strong temporal modeling.

Text-to-image (T2I) generative models have recently emerged as a powerful tool enabling the creation of photo-realistic images and giving rise to a multitude of applications. However the effective integration of T2I models into fundamental image classification tasks remains an open question. A prevalent strategy to bolster image classification performance is through augmenting the training set with synthetic images generated by T2I models. In this study we scrutinize the shortcomings of both current generative and conventional data augmentation techniques. Our analysis reveals that these methods struggle to produce images that are both faithful (in terms of foreground objects) and diverse (in terms of background contexts) for domain-specific concepts. To tackle this challenge we introduce an innovative inter-class data augmentation method known as Diff-Mix (\href https://github.com/Zhicaiwww/Diff-Mix) https://github.com/Zhicaiwww/Diff-Mix which enriches the dataset by performing image translations between classes. Our empirical results demonstrate that Diff-Mix achieves a better balance between faithfulness and diversity leading to a marked improvement in performance across diverse image classification scenarios including few-shot conventional and long-tail classifications for domain-specific datasets.

The Segment Anything Model (SAM) a prompt-driven foundational model has demonstrated remarkable performance in natural image segmentation. However its application in video camouflaged object detection (VCOD) encounters challenges chiefly stemming from the overlooked temporal-spatial associations and the unreliability of user-provided prompts for camouflaged objects that are difficult to discern with the naked eye. To tackle the above issues we endow SAM with keen eyes and propose the Temporal-spatial Prompt SAM (TSP-SAM) a novel approach tailored for VCOD via an ingenious prompted learning scheme. Firstly motion-driven self-prompt learning is employed to capture the camouflaged object thereby bypassing the need for user-provided prompts. With the detected subtle motion cues across consecutive video frames the overall movement of the camouflaged object is captured for more precise spatial localization. Subsequently to eliminate the prompt bias resulting from inter-frame discontinuities the long-range consistency within the video sequences is taken into account to promote the robustness of the self-prompts. It is also injected into the encoder of SAM to enhance the representational capabilities. Extensive experimental results on two benchmarks demonstrate that the proposed TSP-SAM achieves a significant improvement over the state-of-the-art methods. With the mIoU metric increasing by 7.8% and 9.6% TSP-SAM emerges as a groundbreaking step forward in the field of VCOD.

Recently temporal action detection (TAD) has seen significant performance improvement with end-to-end training. However due to the memory bottleneck only models with limited scales and limited data volumes can afford end-to-end training which inevitably restricts TAD performance. In this paper we reduce the memory consumption for end-to-end training and manage to scale up the TAD backbone to 1 billion parameters and the input video to 1536 frames leading to significant detection performance. The key to our approach lies in our proposed temporal-informative adapter (TIA) which is a novel lightweight module that reduces training memory. Using TIA we free the humongous backbone from learning to adapt to the TAD task by only updating the parameters in TIA. TIA also leads to better TAD representation by temporally aggregating context from adjacent frames throughout the backbone. We evaluate our model across four representative datasets. Owing to our efficient design we are able to train end-to-end on VideoMAEv2-giant and achieve 75.4% mAP on THUMOS14 being the first end-to-end model to outperform the best feature-based methods.

The most performant spatio-temporal action localisation models use external person proposals and complex external memory banks. We propose a fully end-to-end transformer based model that directly ingests an input video and outputs tubelets -- a sequence of bounding boxes and the action classes at each frame. Our flexible model can be trained with either sparse bounding-box supervision on individual frames or full tubelet annotations. And in both cases it predicts coherent tubelets as the output. Moreover our end-to-end model requires no additional pre-processing in the form of proposals or post-processing in terms of non-maximal suppression. We perform extensive ablation experiments and significantly advance the state-of-the-art on five different spatio-temporal action localisation benchmarks with both sparse keyframes and full tubelet annotations.