CVPR 2024 Papers

Existing few-shot segmentation methods usually extract foreground prototypes from support images to guide query image segmentation. However different background contexts of support and query images can cause their foreground features to be misaligned. This phenomenon known as background context bias can hinder the effectiveness of support prototypes in guiding query image segmentation. In this work we propose a novel framework with an iterative structure to address this problem. In each iteration of the framework we first generate a query prediction based on a support foreground feature. Next we extract background context from the query image to modulate the support foreground feature thus eliminating the foreground feature misalignment caused by the different backgrounds. After that we design a confidence-biased attention to eliminate noise and cleanse information. By integrating these components through an iterative structure we create a novel network that can leverage the synergies between different modules to improve their performance in a mutually reinforcing manner. Through these carefully designed components and structures our network can effectively eliminate background context bias in few-shot segmentation thus achieving outstanding performance. We conduct extensive experiments on the PASCAL-5^ i and COCO-20^ i datasets and achieve state-of-the-art (SOTA) results which demonstrate the effectiveness of our approach.

Visual-inertial odometry (VIO) has demonstrated remarkable success due to its low-cost and complementary sensors. However existing VIO methods lack the generalization ability to adjust to different environments and sensor attributes. In this paper we propose Adaptive VIO a new monocular visual-inertial odometry that combines online continual learning with traditional nonlinear optimization. Adaptive VIO comprises two networks to predict visual correspondence and IMU bias. Unlike end-to-end approaches that use networks to fuse the features from two modalities (camera and IMU) and predict poses directly we combine neural networks with visual-inertial bundle adjustment in our VIO system. The optimized estimates will be fed back to the visual and IMU bias networks refining the networks in a self-supervised manner. Such a learning-optimization-combined framework and feedback mechanism enable the system to perform online continual learning. Experiments demonstrate that our Adaptive VIO manifests adaptive capability on EuRoC and TUM-VI datasets. The overall performance exceeds the currently known learning-based VIO methods and is comparable to the state-of-the-art optimization-based methods.

Softassign is a pivotal method in graph matching and other learning tasks. Many softassign-based algorithms exhibit performance sensitivity to a parameter in the softassign. However tuning the parameter is challenging and almost done empirically. This paper proposes an adaptive softassign method for graph matching by analyzing the relationship between the objective score and the parameter. This method can automatically tune the parameter based on a given error bound to guarantee accuracy. The Hadamard-Equipped Sinkhorn formulas introduced in this study significantly enhance the efficiency and stability of the adaptive softassign. Moreover these formulas can also be used in optimal transport problems. The resulting adaptive softassign graph matching algorithm enjoys significantly higher accuracy than previous state-of-the-art large graph matching algorithms while maintaining comparable efficiency.

Object-centric learning (OCL) extracts the representation of objects with slots offering an exceptional blend of flexibility and interpretability for abstracting low-level perceptual features. A widely adopted method within OCL is slot attention which utilizes attention mechanisms to iteratively refine slot representations. However a major drawback of most object-centric models including slot attention is their reliance on predefining the number of slots. This not only necessitates prior knowledge of the dataset but also overlooks the inherent variability in the number of objects present in each instance. To overcome this fundamental limitation we present a novel complexity-aware object auto-encoder framework. Within this framework we introduce an adaptive slot attention (AdaSlot) mechanism that dynamically determines the optimal number of slots based on the content of the data. This is achieved by proposing a discrete slot sampling module that is responsible for selecting an appropriate number of slots from a candidate list. Furthermore we introduce a masked slot decoder that suppresses unselected slots during the decoding process. Our framework tested extensively on object discovery tasks with various datasets shows performance matching or exceeding top fixed-slot models. Moreover our analysis substantiates that our method exhibits the capability to dynamically adapt the slot number according to each instance's complexity offering the potential for further exploration in slot attention research. Project will be available at https://kfan21.github.io/AdaSlot/

While fine-tuning is a de facto standard method for training deep neural networks it still suffers from overfitting when using small target datasets. Previous methods improve fine-tuning performance by maintaining knowledge of the source datasets or introducing regularization terms such as contrastive loss. However these methods require auxiliary source information (e.g. source labels or datasets) or heavy additional computations. In this paper we propose a simple method called adaptive random feature regularization (AdaRand). AdaRand helps the feature extractors of training models to adaptively change the distribution of feature vectors for downstream classification tasks without auxiliary source information and with reasonable computation costs. To this end AdaRand minimizes the gap between feature vectors and random reference vectors that are sampled from class conditional Gaussian distributions. Furthermore AdaRand dynamically updates the conditional distribution to follow the currently updated feature extractors and balance the distance between classes in feature spaces. Our experiments show that AdaRand outperforms the other fine-tuning regularization requiring auxiliary source information and heavy computation costs.

Despite the great success of deep learning in stereo matching recovering accurate disparity maps is still challenging. Currently L1 and cross-entropy are the two most widely used losses for stereo network training. Compared with the former the latter usually performs better thanks to its probability modeling and direct supervision to the cost volume. However how to accurately model the stereo ground-truth for cross-entropy loss remains largely under-explored. Existing works simply assume that the ground-truth distributions are uni-modal which ignores the fact that most of the edge pixels can be multi-modal. In this paper a novel adaptive multi-modal cross-entropy loss (ADL) is proposed to guide the networks to learn different distribution patterns for each pixel. Moreover we optimize the disparity estimator to further alleviate the bleeding or misalignment artifacts in inference. Extensive experimental results show that our method is generic and can help classic stereo networks regain state-of-the-art performance. In particular GANet with our method ranks 1st on both the KITTI 2015 and 2012 benchmarks among the published methods. Meanwhile excellent synthetic-to-realistic generalization performance can be achieved by simply replacing the traditional loss with ours. Code is available at https://github.com/xxxupeng/ADL.

In Federated Learning (FL) the issue of statistical data heterogeneity has been a significant challenge to the field's ongoing development. This problem is further exacerbated when clients' data vary in modalities. In response to these issues of statistical heterogeneity and modality incompatibility we propose the Adaptive Hyper-graph Aggregation framework a novel solution for Modality-Agnostic Federated Learning. We design a Modular Architecture for Local Model with single modality setting the stage for efficient intra-modality sharing and inter-modality complementarity. An innovative Global Consensus Prototype Enhancer is crafted to assimilate and broadcast global consensus knowledge within the network. At the core of our approach lies the Adaptive Hyper-graph Learning Strategy which effectively tackles the inherent challenges of modality incompatibility and statistical heterogeneity within federated learning environments accomplishing this adaptively even without the server being aware of the clients' modalities. Our approach tested on three multimodal benchmark datasets demonstrated strong performance across diverse data distributions affirming its effectiveness in multimodal federated learning.

Multi-view depth estimation has achieved impressive performance over various benchmarks. However almost all current multi-view systems rely on given ideal camera poses which are unavailable in many real-world scenarios such as autonomous driving. In this work we propose a new robustness benchmark to evaluate the depth estimation system under various noisy pose settings. Surprisingly we find current multi-view depth estimation methods or single-view and multi-view fusion methods will fail when given noisy pose settings. To address this challenge we propose a single-view and multi-view fused depth estimation system which adaptively integrates high-confident multi-view and single-view results for both robust and accurate depth estimations. The adaptive fusion module performs fusion by dynamically selecting high-confidence regions between two branches based on a wrapping confidence map. Thus the system tends to choose the more reliable branch when facing textureless scenes inaccurate calibration dynamic objects and other degradation or challenging conditions. Our method outperforms state-of-the-art multi-view and fusion methods under robustness testing. Furthermore we achieve state-of-the-art performance on challenging benchmarks (KITTI and DDAD) when given accurate pose estimations. Project website: https://github.com/Junda24/AFNet/

Consistency learning is a central strategy to tackle unlabeled data in semi-supervised medical image segmentation (SSMIS) which enforces the model to produce consistent predictions under the perturbation. However most current approaches solely focus on utilizing a specific single perturbation which can only cope with limited cases while employing multiple perturbations simultaneously is hard to guarantee the quality of consistency learning. In this paper we propose an Adaptive Bidirectional Displacement (ABD) approach to solve the above challenge. Specifically we first design a bidirectional patch displacement based on reliable prediction confidence for unlabeled data to generate new samples which can effectively suppress uncontrollable regions and still retain the influence of input perturbations. Meanwhile to enforce the model to learn the potentially uncontrollable content a bidirectional displacement operation with inverse confidence is proposed for the labeled images which generates samples with more unreliable information to facilitate model learning. Extensive experiments show that ABD achieves new state-of-the-art performances for SSMIS significantly improving different baselines. Source code is available at https://github.com/chy-upc/ABD.

Trajectory prediction plays an important role in various applications including autonomous driving robotics and scene understanding. Existing approaches mainly focus on developing compact neural networks to increase prediction precision on public datasets typically employing a standardized input duration. However a notable issue arises when these models are evaluated with varying observation lengths leading to a significant performance drop a phenomenon we term the Observation Length Shift. To address this issue we introduce a general and effective framework the FlexiLength Network (FLN) to enhance the robustness of existing trajectory prediction techniques against varying observation periods. Specifically FLN integrates trajectory data with diverse observation lengths incorporates FlexiLength Calibration (FLC) to acquire temporal invariant representations and employs FlexiLength Adaptation (FLA) to further refine these representations for more accurate future trajectory predictions. Comprehensive experiments on multiple datasets i.e. ETH/UCY nuScenes and Argoverse 1 demonstrate the effectiveness and flexibility of our proposed FLN framework.

Vision Transformer (ViT) has shown high potential in video recognition owing to its flexible design adaptable self-attention mechanisms and the efficacy of masked pre-training. Yet it remains unclear how to adapt these pre-trained short-term ViTs for temporal action detection (TAD) in untrimmed videos. The existing works treat them as off-the-shelf feature extractors for each short-trimmed snippet without capturing the fine-grained relation among different snippets in a broader temporal context. To mitigate this issue this paper focuses on designing a new mechanism for adapting these pre-trained ViT models as a unified long-form video transformer to fully unleash its modeling power in capturing inter-snippet relation while still keeping low computation overhead and memory consumption for efficient TAD. To this end we design effective cross-snippet propagation modules to gradually exchange short-term video information among different snippets from two levels. For inner-backbone information propagation we introduce a cross-snippet propagation strategy to enable multi-snippet temporal feature interaction inside the backbone. For post-backbone information propagation we propose temporal transformer layers for further clip-level modeling. With the plain ViT-B pre-trained with VideoMAE our end-to-end temporal action detector (ViT-TAD) yields a very competitive performance to previous temporal action detectors riching up to 69.5 average mAP on THUMOS14 37.40 average mAP on ActivityNet-1.3 and 17.20 average mAP on FineAction.

Adapters provide an efficient and lightweight mechanism for adapting trained transformer models to a variety of different tasks. However they have often been found to be outperformed by other adaptation mechanisms including low-rank adaptation. In this paper we provide an in-depth study of adapters their internal structure as well as various implementation choices. We uncover pitfalls for using adapters and suggest a concrete improved adapter architecture called Adapter+ that not only outperforms previous adapter implementations but surpasses a number of other more complex adaptation mechanisms in several challenging settings. Despite this our suggested adapter is highly robust and unlike previous work requires little to no manual intervention when addressing a novel scenario. Adapter+ reaches state-of-the-art average accuracy on the VTAB benchmark even without a per-task hyperparameter optimization.

Transformer-based approaches have achieved promising performance in image restoration tasks given their ability to model long-range dependencies which is crucial for recovering clear images. Though diverse efficient attention mechanism designs have addressed the intensive computations associated with using transformers they often involve redundant information and noisy interactions from irrelevant regions by considering all available tokens. In this work we propose an Adaptive Sparse Transformer (AST) to mitigate the noisy interactions of irrelevant areas and remove feature redundancy in both spatial and channel domains. AST comprises two core designs i.e. an Adaptive Sparse Self-Attention (ASSA) block and a Feature Refinement Feed-forward Network (FRFN). Specifically ASSA is adaptively computed using a two-branch paradigm where the sparse branch is introduced to filter out the negative impacts of low query-key matching scores for aggregating features while the dense one ensures sufficient information flow through the network for learning discriminative representations. Meanwhile FRFN employs an enhance-and-ease scheme to eliminate feature redundancy in channels enhancing the restoration of clear latent images. Experimental results on commonly used benchmarks have demonstrated the versatility and competitive performance of our method in several tasks including rain streak removal real haze removal and raindrop removal. The code and pre-trained models are available at https://github.com/joshyZhou/AST.

Few-shot segmentation performance declines substantially when facing images from a domain different than the training domain effectively limiting real-world use cases. To alleviate this recently cross-domain few-shot segmentation (CD-FSS) has emerged. Works that address this task mainly attempted to learn segmentation on a source domain in a manner that generalizes across domains. Surprisingly we can outperform these approaches while eliminating the training stage and removing their main segmentation network. We show test-time task-adaption is the key for successful CD-FSS instead. Task-adaption is achieved by appending small networks to the feature pyramid of a conventionally classification-pretrained backbone. To avoid overfitting to the few labeled samples in supervised fine-tuning consistency across augmented views of input images serves as guidance while learning the parameters of the attached layers. Despite our self-restriction not to use any images other than the few labeled samples at test time we achieve new state-of-the-art performance in CD-FSS evidencing the need to rethink approaches for the task. Code is available at https://github.com/Vision-Kek/ABCDFSS.

Nonlinearities are decisive in neural representation learning. Traditional Activation (Act) functions impose fixed inductive biases on neural networks with oriented biological intuitions. Recent methods leverage self-gated curves to compensate for the rigid traditional Act paradigms in fitting flexibility. However substantial improvements are still impeded by the norm-induced mismatched feature re-calibrations (see Section 1) i.e. the actual importance of a feature can be inconsistent with its explicit intensity such that violates the basic intention of a direct self-gated feature re-weighting. To address this problem we propose to learn discriminative neural feature Act with a novel prototype namely AdaShift which enhances typical self-gated Act by incorporating an adaptive shift factor into the re-weighting function of Act. AdaShift casts dynamic translations on the inputs of a re-weighting function by exploiting comprehensive feature-filter context cues of different ranges in a simple yet effective manner. We obtain the new intuitions of AdaShift by rethinking the feature-filter relationships from a common Softmax-based classification and by generalizing the new observations to a common learning layer that encodes features with updatable filters. Our practical AdaShifts built upon the new Act prototype demonstrate significant improvements to the popular/SOTA Act functions on different vision benchmarks. By simply replacing ReLU with AdaShifts ResNets can match advanced Transformer counterparts (e.g. ResNet-50 vs. Swin-T) with lower cost and fewer parameters.

Despite the recent progress in enhancing the efficacy of image deblurring the limited decoding capability constrains the upper limit of State-Of-The-Art (SOTA) methods. This paper proposes a pioneering work Adaptive Patch Exiting Reversible Decoder (AdaRevD) to explore their insufficient decoding capability. By inheriting the weights of the well-trained encoder we refactor a reversible decoder which scales up the single-decoder training to multi-decoder training while remaining GPU memory-friendly. Meanwhile we show that our reversible structure gradually disentangles high-level degradation degree and low-level blur pattern (residual of the blur image and its sharp counterpart) from compact degradation representation. Besides due to the spatially-variant motion blur kernels different blur patches have various deblurring difficulties. We further introduce a classifier to learn the degradation degree of image patches enabling them to exit at different sub-decoders for speedup. Experiments show that our AdaRevD pushes the limit of image deblurring e.g. achieving 34.60 dB in PSNR on GoPro dataset.

Although image super-resolution (SR) problem has experienced unprecedented restoration accuracy with deep neural networks it has yet limited versatile applications due to the substantial computational costs. Since different input images for SR face different restoration difficulties adapting computational costs based on the input image referred to as adaptive inference has emerged as a promising solution to compress SR networks. Specifically adapting the quantization bit-widths has successfully reduced the inference and memory cost without sacrificing the accuracy. However despite the benefits of the resultant adaptive network existing works rely on time-intensive quantization-aware training with full access to the original training pairs to learn the appropriate bit allocation policies which limits its ubiquitous usage. To this end we introduce the first on-the-fly adaptive quantization framework that accelerates the processing time from hours to seconds. We formulate the bit allocation problem with only two bit mapping modules: one to map the input image to the image-wise bit adaptation factor and one to obtain the layer-wise adaptation factors. These bit mappings are calibrated and fine-tuned using only a small number of calibration images. We achieve competitive performance with the previous adaptive quantization methods while the processing time is accelerated by x2000. Codes are available at https://github.com/Cheeun/AdaBM.

In this work we study a novel problem which focuses on person identification while performing daily activities. Learning biometric features from RGB videos is challenging due to spatio-temporal complexity and presence of appearance biases such as clothing color and background. We propose ABNet a novel framework which leverages disentanglement of biometric and non-biometric features to perform effective person identification from daily activities. ABNet relies on a bias-less teacher to learn biometric features from RGB videos and explicitly disentangle non-biometric features with the help of biometric distortion. In addition ABNet also exploits activity prior for biometrics which is enabled by joint biometric and activity learning. We perform comprehensive evaluation of the proposed approach across five different datasets which are derived from existing activity recognition benchmarks. Furthermore we extensively compare ABNet with existing works in person identification and demonstrate its effectiveness for activity-based biometrics across all five datasets. The code and dataset can be accessed at: https://github.com/sacrcv/Activity-Biometrics/

The pretraining-finetuning paradigm has gained popularity in various computer vision tasks. In this paradigm the emergence of active finetuning arises due to the abundance of large-scale data and costly annotation requirements. Active finetuning involves selecting a subset of data from an unlabeled pool for annotation facilitating subsequent finetuning. However the use of a limited number of training samples can lead to a biased distribution potentially resulting in model overfitting. In this paper we propose a new method called ActiveDC for the active finetuning tasks. Firstly we select samples for annotation by optimizing the distribution similarity between the subset to be selected and the entire unlabeled pool in continuous space. Secondly we calibrate the distribution of the selected samples by exploiting implicit category information in the unlabeled pool. The feature visualization provides an intuitive sense of the effectiveness of our approach to distribution calibration. We conducted extensive experiments on three image classification datasets with different sampling ratios. The results indicate that ActiveDC consistently outperforms the baseline performance in all image classification tasks. The improvement is particularly significant when the sampling ratio is low with performance gains of up to 10%. Our code will be released.