CVPR 2024 Papers

Monocular 3D object detection has attracted widespread attention due to its potential to accurately obtain object 3D localization from a single image at a low cost. Depth estimation is an essential but challenging subtask of monocular 3D object detection due to the ill-posedness of 2D to 3D mapping. Many methods explore multiple local depth clues such as object heights and keypoints and then formulate the object depth estimation as an ensemble of multiple depth predictions to mitigate the insufficiency of single-depth information. However the errors of existing multiple depths tend to have the same sign which hinders them from neutralizing each other and limits the overall accuracy of combined depth. To alleviate this problem we propose to increase the complementarity of depths with two novel designs. First we add a new depth prediction branch named complementary depth that utilizes global and efficient depth clues from the entire image rather than the local clues to reduce the correlation of depth predictions. Second we propose to fully exploit the geometric relations between multiple depth clues to achieve complementarity in form. Benefiting from these designs our method achieves higher complementarity. Experiments on the KITTI benchmark demonstrate that our method achieves state-of-the-art performance without introducing extra data. In addition complementary depth can also be a lightweight and plug-and-play module to boost multiple existing monocular 3d object detectors. Code is available at https://github.com/elvintanhust/MonoCD.

Large Vision-Language Models (LVLMs) have advanced considerably intertwining visual recognition and language understanding to generate content that is not only coherent but also contextually attuned. Despite their success LVLMs still suffer from the issue of object hallucinations where models generate plausible yet incorrect outputs that include objects that do not exist in the images. To mitigate this issue we introduce Visual Contrastive Decoding (VCD) a simple and training-free method that contrasts output distributions derived from original and distorted visual inputs. The proposed VCD effectively reduces the over-reliance on statistical bias and unimodal priors two essential causes of object hallucinations. This adjustment ensures the generated content is closely grounded to visual inputs resulting in contextually accurate outputs. Our experiments show that VCD without either additional training or the usage of external tools significantly mitigates the object hallucination issue across different LVLM families. Beyond mitigating object hallucinations VCD also excels in general LVLM benchmarks highlighting its wide-ranging applicability.

In the realm of point cloud scene understanding particularly in indoor scenes objects are arranged following human habits resulting in objects of certain semantics being closely positioned and displaying notable inter-object correlations. This can create a tendency for neural networks to exploit these strong dependencies bypassing the individual object patterns. To address this challenge we introduce a novel self-supervised learning (SSL) strategy. Our approach leverages both object patterns and contextual cues to produce robust features. It begins with the formulation of an object-exchanging strategy where pairs of objects with comparable sizes are exchanged across different scenes effectively disentangling the strong contextual dependencies. Subsequently we introduce a context-aware feature learning strategy which encodes object patterns without relying on their specific context by aggregating object features across various scenes. Our extensive experiments demonstrate the superiority of our method over existing SSL techniques further showing its better robustness to environmental changes. Moreover we showcase the applicability of our approach by transferring pre-trained models to diverse point cloud datasets.

The robust association of the same objects across video frames in complex scenes is crucial for many applications especially object tracking. Current methods predominantly rely on labeled domain-specific video datasets which limits cross-domain generalization of learned similarity embeddings. We propose MASA a novel method for robust instance association learning capable of matching any objects within videos across diverse domains without tracking labels. Leveraging the rich object segmentation from the Segment Anything Model (SAM) MASA learns instance-level correspondence through exhausive data transformations. We treat the SAM outputs as dense object region proposals and learn to match those regions from a vast image collection. We further design a universal MASA adapter which can work in tandem with foundational segmentation or detection models and enable them to track any detected objects. Those combinations present strong zero-shot tracking ability in complex domains. Extensive tests on multiple challenging MOT and MOTS benchmarks indicate that the proposed method using only unlabelled static images achieves even better performance than state-of-the-art methods trained with fully annotated in-domain video sequences in zero-shot association. Our code is available at https://github.com/siyuanliii/masa.

Single-modal object re-identification (ReID) faces great challenges in maintaining robustness within complex visual scenarios. In contrast multi-modal object ReID utilizes complementary information from diverse modalities showing great potentials for practical applications. However previous methods may be easily affected by irrelevant backgrounds and usually ignore the modality gaps. To address above issues we propose a novel learning framework named EDITOR to select diverse tokens from vision Transformers for multi-modal object ReID. We begin with a shared vision Transformer to extract tokenized features from different input modalities. Then we introduce a Spatial-Frequency Token Selection (SFTS) module to adaptively select object-centric tokens with both spatial and frequency information. Afterwards we employ a Hierarchical Masked Aggregation (HMA) module to facilitate feature interactions within and across modalities. Finally to further reduce the effect of backgrounds we propose a Background Consistency Constraint (BCC) and an Object-Centric Feature Refinement (OCFR). They are formulated as two new loss functions which improve the feature discrimination with background suppression. As a result our framework can generate more discriminative features for multi-modal object ReID. Extensive experiments on three multi-modal ReID benchmarks verify the effectiveness of our methods. The code is available at https://github.com/924973292/EDITOR.

We propose a novel approach to video anomaly detection: we treat feature vectors extracted from videos as realizations of a random variable with a fixed distribution and model this distribution with a neural network. This lets us estimate the likelihood of test videos and detect video anomalies by thresholding the likelihood estimates. We train our video anomaly detector using a modification of denoising score matching a method that injects training data with noise to facilitate modeling its distribution. To eliminate hyperparameter selection we model the distribution of noisy video features across a range of noise levels and introduce a regularizer that tends to align the models for different levels of noise. At test time we combine anomaly indications at multiple noise scales with a Gaussian mixture model. Running our video anomaly detector induces minimal delays as inference requires merely extracting the features and forward-propagating them through a shallow neural network and a Gaussian mixture model. Our experiments on five popular video anomaly detection benchmarks demonstrate state-of-the-art performance both in the object-centric and in the frame-centric setup.

DETR accomplishes end-to-end object detection through iteratively generating multiple object candidates based on image features and promoting one candidate for each ground-truth object. The traditional training procedure using one-to-one supervision in the original DETR lacks direct supervision for the object detection candidates. We aim at improving the DETR training efficiency by explicitly supervising the candidate generation procedure through mixing one-to-one supervision and one-to-many supervision. Our approach namely MS-DETR is simple and places one-to-many supervision to the object queries of the primary decoder that is used for inference. In comparison to existing DETR variants with one-to-many supervision such as Group DETR and Hybrid DETR our approach does not need additional decoder branches or object queries. The object queries of the primary decoder in our approach directly benefit from one-to-many supervision and thus are superior in object candidate prediction. Experimental results show that our approach outperforms related DETR variants such as DN-DETR Hybrid DETR and Group DETR and the combination with related DETR variants further improves the performance.

Previous works concerning single-view hand-held object reconstruction typically rely on supervision from 3D ground-truth models which are hard to collect in real world. In contrast readily accessible hand-object videos offer a promising training data source but they only give heavily occluded object observations. In this paper we present a novel synthetic-to-real framework to exploit Multi-view Occlusion-aware supervision from hand-object videos for Hand-held Object reconstruction (MOHO) from a single image tackling two predominant challenges in such setting: hand-induced occlusion and object's self-occlusion. First in the synthetic pre-training stage we render a large-scaled synthetic dataset SOMVideo with hand-object images and multi-view occlusion-free supervisions adopted to address hand-induced occlusion in both 2D and 3D spaces. Second in the real-world finetuning stage MOHO leverages the amodal-mask-weighted geometric supervision to mitigate the unfaithful guidance caused by the hand-occluded supervising views in real world. Moreover domain-consistent occlusion-aware features are amalgamated in MOHO to resist object's self-occlusion for inferring the complete object shape. Extensive experiments on HO3D and DexYCB datasets demonstrate 2D-supervised MOHO gains superior results against 3D-supervised methods by a large margin.

The anatomical structure detection of fetal cardiac views is crucial for diagnosing fetal congenital heart disease. In practice there is a large domain gap between different hospitals' data such as the variable data quality due to differences in acquisition equipment. In addition accurate annotation information provided by obstetrician experts is always very costly or even unavailable. This study explores the unsupervised domain adaptive fetal cardiac structure detection issue. Existing unsupervised domain adaptive object detection (UDAOD) approaches mainly focus on detecting objects in natural scenes such as Foggy Cityscapes where the structural relationships of natural scenes are uncertain. Unlike all previous UDAOD scenarios we first collected a Fetal Cardiac Structure dataset from two hospital centers called FCS and proposed a multi-matching UDA approach (M3-UDA) including Histogram Matching (HM) Sub-structure Matching (SM) and Global-structure Matching (GM) to better transfer the topological knowledge of anatomical structure for UDA detection in medical scenarios. HM mitigates the domain gap between the source and target caused by pixel transformation. SM fuses the different angle information of the sub-structure to obtain the local topological knowledge for bridging the domain gap of the internal sub-structure. GM is designed to align the global topological knowledge of the whole organ from the source and target domain. Extensive experiments on our collected FCS and CardiacUDA and experimental results show that M3-UDA outperforms existing UDAOD studies significantly. All datasets and source code are available at : https://github.com/xmed-lab/M3-UDA

Researchers in natural science need reliable methods for quantifying animal behavior. Recently numerous computer vision methods emerged to automate the process. However observing wild species at remote locations remains a challenging task due to difficult lighting conditions and constraints on power supply and data storage. Event cameras offer unique advantages for battery-dependent remote monitoring due to their low power consumption and high dynamic range capabilities. We use this novel sensor to quantify a behavior in Chinstrap penguins called ecstatic display. We formulate the problem as a temporal action detection task determining the start and end times of the behavior. For this purpose we recorded a colony of breeding penguins in Antarctica for several weeks and labeled event data on 16 nests. The developed method consists of a generator of candidate time intervals (proposals) and a classifier of the actions within them. The experiments show that the event cameras' natural response to motion is effective for continuous behavior monitoring and detection reaching a mean average precision (mAP) of 58% (which increases to 63% in good weather conditions). The results also demonstrate the robustness against various lighting conditions contained in the challenging dataset. The low-power capabilities of the event camera allow it to record significantly longer than with a conventional camera. This work pioneers the use of event cameras for remote wildlife observation opening new interdisciplinary opportunities. https:// tub-rip.github.io/ eventpenguins/

Automatic anomaly detection based on visual cues holds practical significance in various domains such as manufacturing and product quality assessment. This paper introduces a new conditional anomaly detection problem which involves identifying anomalies in a query image by comparing it to a reference shape. To address this challenge we have created a large dataset BrokenChairs-180K consisting of around 180K images with diverse anomalies geometries and textures paired with 8143 reference 3D shapes. To tackle this task we have proposed a novel transformer-based approach that explicitly learns the correspondence between the query image and reference 3D shape via feature alignment and leverages a customized attention mechanism for anomaly detection. Our approach has been rigorously evaluated through comprehensive experiments serving as a benchmark for future research in this domain.

Anomaly detection (AD) aims to identify defective images and localize their defects (if any). Ideally AD models should be able to detect defects over many image classes; without relying on hard-coded class names that can be uninformative or inconsistent across datasets; learn without anomaly supervision; and be robust to the long-tailed distributions of real-world applications. To address these challenges we formulate the problem of long-tailed AD by introducing several datasets with different levels of class imbalance and metrics for performance evaluation. We then propose a novel method LTAD to detect defects from multiple and long-tailed classes without relying on dataset class names. LTAD combines AD by reconstruction and semantic AD modules. AD by reconstruction is implemented with a transformer-based reconstruction module. Semantic AD is implemented with a binary classifier which relies on learned pseudo class names and a pretrained foundation model. These modules are learned over two phases. Phase 1 learns the pseudo-class names and a variational autoencoder (VAE) for feature synthesis that augments the training data to combat long-tails. Phase 2 then learns the parameters of the reconstruction and classification modules of LTAD. Extensive experiments using the proposed long-tailed datasets show that LTAD substantially outperforms the state-of-the-art methods for most forms of dataset imbalance. The long-tailed dataset split is available at https://zenodo.org/records/10854201

Active Speaker Detection (ASD) aims to identify who is speaking in each frame of a video. Solving ASD involves using audio and visual information in two complementary contexts: long-term intra-speaker context models the temporal dependencies of the same speaker while short-term inter-speaker context models the interactions of speakers in the same scene. Motivated by these observations we propose LoCoNet a simple but effective Long-Short Context Network that leverages Long-term Intra-speaker Modeling (LIM) and Short-term Inter-speaker Modeling (SIM) in an interleaved manner. LIM employs self-attention for long-range temporal dependencies modeling and cross-attention for audio-visual interactions modeling. SIM incorporates convolutional blocks that capture local patterns for short-term inter-speaker context. Experiments show that LoCoNet achieves state-of-the-art performance on multiple datasets with 95.2% (+0.3%) mAP on AVA-ActiveSpeaker 97.2% (+2.7%) mAP on Talkies and 68.4% (+7.7%) mAP on Ego4D. Moreover in challenging cases where multiple speakers are present LoCoNet outperforms previous state-of-the-art methods by 3.0% mAP on AVA-ActiveSpeaker. The code is available at https://github.com/SJTUwxz/LoCoNet_ASD.

Research into dynamic 3D scene understanding has primarily focused on short-term change tracking from dense observations while little attention has been paid to long-term changes with sparse observations. We address this gap with MoRE a novel approach for multi-object relocalization and reconstruction in evolving environments. We view these environments as Living Scenes and consider the problem of transforming scans taken at different points in time into a 3D reconstruction of the object instances whose accuracy and completeness increase over time. At the core of our method lies an SE(3) equivariant representation in a single encoder-decoder network trained on synthetic data. This representation enables us to seamlessly tackle instance matching registration and reconstruction. We also introduce a joint optimization algorithm that facilitates the accumulation of point clouds originating from the same instance across multiple scans taken at different points in time. We validate our method on synthetic and real-world data and demonstrate state-of-the-art performance in both end-to-end performance and individual subtasks.

Existing prompt learning methods have shown certain capabilities in Out-of-Distribution (OOD) detection but the lack of OOD images in the target dataset in their training can lead to mismatches between OOD images and In-Distribution (ID) categories resulting in a high false positive rate. To address this issue we introduce a novel OOD detection method named 'NegPrompt' to learn a set of negative prompts each representing a negative connotation of a given class label for delineating the boundaries between ID and OOD images. It learns such negative prompts with ID data only without any reliance on external outlier data. Further current methods assume the availability of samples of all ID classes rendering them ineffective in open-vocabulary learning scenarios where the inference stage can contain novel ID classes not present during training. In contrast our learned negative prompts are transferable to novel class labels. Experiments on various ImageNet benchmarks show that NegPrompt surpasses state-of-the-art prompt-learning-based OOD detection methods and maintains a consistent lead in hard OOD detection in closed- and open-vocabulary classification scenarios. Code is available at https://github.com/mala-lab/negprompt.

Monocular 3D detection is a challenging task due to the lack of accurate 3D information. Existing approaches typically rely on geometry constraints and dense depth estimates to facilitate the learning but often fail to fully exploit the benefits of three-dimensional feature extraction in frustum and 3D space. In this paper we propose OccupancyM3D a method of learning occupancy for monocular 3D detection. It directly learns occupancy in frustum and 3D space leading to more discriminative and informative 3D features and representations. Specifically by using synchronized raw sparse LiDAR point clouds we define the space status and generate voxel-based occupancy labels. We formulate occupancy prediction as a simple classification problem and design associated occupancy losses. Resulting occupancy estimates are employed to enhance original frustum/3D features. As a result experiments on KITTI and Waymo open datasets demonstrate that the proposed method achieves a new state of the art and surpasses other methods by a significant margin.

Object State Changes (OSCs) are pivotal for video understanding. While humans can effortlessly generalize OSC understanding from familiar to unknown objects current approaches are confined to a closed vocabulary. Addressing this gap we introduce a novel open-world formulation for the video OSC problem. The goal is to temporally localize the three stages of an OSC---the object's initial state its transitioning state and its end state---whether or not the object has been observed during training. Towards this end we develop VidOSC a holistic learning approach that: (1) leverages text and vision-language models for supervisory signals to obviate manually labeling OSC training data and (2) abstracts fine-grained shared state representations from objects to enhance generalization. Furthermore we present HowToChange the first open-world benchmark for video OSC localization which offers an order of magnitude increase in the label space and annotation volume compared to the best existing benchmark. Experimental results demonstrate the efficacy of our approach in both traditional closed-world and open-world scenarios.

Label noise commonly found in real-world datasets has a detrimental impact on a model's generalization. To effectively detect incorrectly labeled instances previous works have mostly relied on distinguishable training signals such as training loss as indicators to differentiate between clean and noisy labels. However they have limitations in that the training signals incompletely reveal the model's behavior and are not effectively generalized to various noise types resulting in limited detection accuracy. In this paper we propose DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones based on the dynamics of the training signals. To cope with the absence of supervision for clean and noisy labels DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels enabling indirect simulation of the model's behavior on noisy labels. Then DynaCor learns to identify clean and noisy instances by inducing two clearly distinguishable clusters from the latent representations of training dynamics. Our comprehensive experiments show that DynaCor outperforms the state-of-the-art competitors and shows strong robustness to various noise types and noise rates.

Open vocabulary object detection (OVD) aims at seeking an optimal object detector capable of recognizing objects from both base and novel categories. Recent advances leverage knowledge distillation to transfer insightful knowledge from pre-trained large-scale vision-language models to the task of object detection significantly generalizing the powerful capabilities of the detector to identify more unknown object categories. However these methods face significant challenges in background interpretation and model overfitting and thus often result in the loss of crucial background knowledge giving rise to sub-optimal inference performance of the detector. To mitigate these issues we present a novel OVD framework termed LBP to propose learning background prompts to harness explored implicit background knowledge thus enhancing the detection performance w.r.t. base and novel categories. Specifically we devise three modules: Background Category-specific Prompt Background Object Discovery and Inference Probability Rectification to empower the detector to discover represent and leverage implicit object knowledge explored from background proposals. Evaluation on two benchmark datasets OV-COCO and OV-LVIS demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks.