CVPR 2024 Papers

Recent advances in unsupervised learning have demonstrated the ability of large vision models to achieve promising results on downstream tasks by pre-training on large amount of unlabelled data. Such pre-training techniques have also been explored recently in the remote sensing domain due to the availability of large amount of unlabelled data. Different from standard natural image datasets remote sensing data is acquired from various sensor technologies and exhibit diverse range of scale variations as well as modalities. Existing satellite image pre-training methods either ignore the scale information present in the remote sensing imagery or restrict themselves to use only a single type of data modality. In this paper we re-visit transformers pre-training and leverage multi-scale information that is effectively utilized with multiple modalities. Our proposed approach named SatMAE++ performs multi-scale pre-training and utilizes convolution based upsampling blocks to reconstruct the image at higher scales making it extensible to include more scales. Compared to existing works the proposed SatMAE++ with multi-scale pre-training is equally effective for both optical as well as multi-spectral imagery. Extensive experiments on six datasets reveal the merits of proposed contributions leading to state-of-the-art performance on all datasets. SatMAE++ achieves mean average precision (mAP) gain of 2.5% for multi-label classification task on BigEarthNet dataset.

Multi-view representation learning aims to derive robust representations that are both view-consistent and view-specific from diverse data sources. This paper presents an in-depth analysis of existing approaches in this domain highlighting a commonly overlooked aspect: the redundancy between view-consistent and view-specific representations. To this end we propose an innovative framework for multi-view representation learning which incorporates a technique we term 'distilled disentangling'. Our method introduces the concept of masked cross-view prediction enabling the extraction of compact high-quality view-consistent representations from various sources without incurring extra computational overhead. Additionally we develop a distilled disentangling module that efficiently filters out consistency-related information from multi-view representations resulting in purer view-specific representations. This approach significantly reduces redundancy between view-consistent and view-specific representations enhancing the overall efficiency of the learning process. Our empirical evaluations reveal that higher mask ratios substantially improve the quality of view-consistent representations. Moreover we find that reducing the dimensionality of view-consistent representations relative to that of view-specific representations further refines the quality of the combined representations.

We investigate whether region-based representations are effective for recognition. Regions were once a mainstay in recognition approaches but pixel and patch-based features are now used almost exclusively. We show that recent class-agnostic segmenters like SAM can be effectively combined with strong unsupervised representations like DINOv2 and used for a wide variety of tasks including semantic segmentation object-based image retrieval and multi-image analysis. Once the masks and features are extracted these representations even with linear decoders enable competitive performance making them well suited to applications that require custom queries. The compactness of the representation also makes it well-suited to video analysis and other problems requiring inference across many images.

The goal of multi-task learning is to learn diverse tasks within a single unified network. As each task has its own unique objective function conflicts emerge during training resulting in negative transfer among them. Earlier research identified these conflicting gradients in shared parameters between tasks and attempted to realign them in the same direction. However we prove that such optimization strategies lead to sub-optimal Pareto solutions due to their inability to accurately determine the individual contributions of each parameter across various tasks. In this paper we propose the concept of task priority to evaluate parameter contributions across different tasks. To learn task priority we identify the type of connections related to links between parameters influenced by task-specific losses during backpropagation. The strength of connections is gauged by the magnitude of parameters to determine task priority. Based on these we present a new method named connection strength-based optimization for multi-task learning which consists of two phases. The first phase learns the task priority within the network while the second phase modifies the gradients while upholding this priority. This ultimately leads to finding new Pareto optimal solutions for multiple tasks. Through extensive experiments we show that our approach greatly enhances multi-task performance in comparison to earlier gradient manipulation methods.

This study targets a critical aspect of multi-modal LLMs' (LLMs&VLMs) inference: explicit controllable text generation. Multi-modal LLMs empower multi-modality understanding with the capability of semantic generation yet bring less explainability and heavier reliance on prompt contents due to their autoregressive generative nature. While manipulating prompt formats could improve outputs designing specific and precise prompts per task can be challenging and ineffective. To tackle this issue we introduce a novel inference method Prompt Highlighter which enables users to highlight specific prompt spans to interactively control the focus during generation. Motivated by the classifier-free diffusion guidance we form regular and unconditional context pairs based on highlighted tokens demonstrating that the autoregressive generation in models can be guided in a classifier-free way. Notably we find that during inference guiding the models with highlighted tokens through the attention weights leads to more desired outputs. Our approach is compatible with current LLMs and VLMs achieving impressive customized generation results without training. Experiments confirm its effectiveness in focusing on input contexts and generating reliable content. Without tuning on LLaVA-v1.5 our method secured 70.7 in the MMBench test and 1552.5 in MME-perception.

Wi-Fi signals in contrast to cameras offer privacy protection and occlusion resilience for some practical scenarios such as smart homes elderly care and virtual reality. Recent years have seen remarkable progress in the estimation of single-person 2D pose single-person 3D pose and multi-person 2D pose. This paper takes a step forward by introducing Person-in-WiFi 3D a pioneering Wi-Fi system that accomplishes multi-person 3D pose estimation. Person-in-WiFi 3D has two main updates. Firstly it has a greater number of Wi-Fi devices to enhance the capability for capturing spatial reflections from multiple individuals. Secondly it leverages the Transformer for end-to-end estimation. Compared to its predecessor Person-in-WiFi 3D is storage-efficient and fast. We deployed a proof-of-concept system in 4mx3.5m areas and collected a dataset of over 97K frames with seven volunteers. Person-in-WiFi 3D attains 3D joint localization errors of 91.7mm (1-person) 108.1mm (2-person) and 125.3mm (3-person) comparable to cameras and millimeter-wave radars.

We present OAKINK2 a dataset of bimanual object manipulation tasks for complex daily activities. In pursuit of constructing the complex tasks into a structured representation OAKINK2 introduces three level of abstraction to organize the manipulation tasks: Affordance Primitive Task and Complex Task. OAKINK2 features on an object-centric perspective for decoding the complex tasks treating them as a sequence of object affordance fulfillment. The first level Affordance outlines the functionalities that objects in the scene can afford the second level Primitive Task describes the minimal interaction units that humans interact with the object to achieve its affordance and the third level Complex Task illustrates how Primitive Tasks are composed and interdependent. OAKINK2 dataset provides multi-view image streams and precise pose annotations for the human body hands and various interacting objects. This extensive collection supports applications such as interaction reconstruction and motion synthesis. Based on the 3-level abstraction of OAKINK2 we explore a task-oriented framework for Complex Task Completion (CTC). CTC aims to generate a sequence of bimanual manipulation to achieve task objectives. Within the CTC framework we employ Large Language Models (LLMs) to decompose the complex task objectives into sequences of Primitive Tasks and have developed a Motion Fulfillment Model that generates bimanual hand motion for each Primitive Task. OAKINK2 datasets and models are available at https://oakink.net/v2.

We present NeLF-Pro a novel representation to model and reconstruct light fields in diverse natural scenes that vary in extent and spatial granularity. In contrast to previous fast reconstruction methods that represent the 3D scene globally we model the light field of a scene as a set of local light field feature probes parameterized with position and multi-channel 2D feature maps. Our central idea is to bake the scene's light field into spatially varying learnable representations and to query point features by weighted blending of probes close to the camera - allowing for mipmap representation and rendering. We introduce a novel vector-matrix-matrix (VMM) factorization technique that effectively represents the light field feature probes as products of core factors (i.e. VM) shared among local feature probes and a basis factor (i.e. M) - efficiently encoding internal relationships and patterns within the scene.Experimentally we demonstrate that NeLF-Pro significantly boosts the performance of feature grid-based representations and achieves fast reconstruction with better rendering quality while maintaining compact modeling. Project page: sinoyou.github.io/nelf-pro

Precise geospatial vegetation forecasting holds potential across diverse sectors including agriculture forestry humanitarian aid and carbon accounting. To leverage the vast availability of satellite imagery for this task various works have applied deep neural networks for predicting multispectral images in photorealistic quality. However the important area of vegetation dynamics has not been thoroughly explored. Our study introduces GreenEarthNet the first dataset specifically designed for high-resolution vegetation forecasting and Contextformer a novel deep learning approach for predicting vegetation greenness from Sentinel 2 satellite images with fine resolution across Europe. Our multi-modal transformer model Contextformer leverages spatial context through a vision backbone and predicts the temporal dynamics on local context patches incorporating meteorological time series in a parameter-efficient manner. The GreenEarthNet dataset features a learned cloud mask and an appropriate evaluation scheme for vegetation modeling. It also maintains compatibility with the existing satellite imagery forecasting dataset EarthNet2021 enabling cross-dataset model comparisons. Our extensive qualitative and quantitative analyses reveal that our methods outperform a broad range of baseline techniques. This includes surpassing previous state-of-the-art models on EarthNet2021 as well as adapted models from time series forecasting and video prediction. To the best of our knowledge this work presents the first models for continental-scale vegetation modeling at fine resolution able to capture anomalies beyond the seasonal cycle thereby paving the way for predicting vegetation health and behaviour in response to climate variability and extremes. We provide open source code and pre-trained weights to reproduce our experimental results under https://github.com/vitusbenson/greenearthnet.

A unified and versatile LiDAR segmentation model with strong robustness and generalizability is desirable for safe autonomous driving perception. This work presents M3Net a one-of-a-kind framework for fulfilling multi-task multi-dataset multi-modality LiDAR segmentation in a universal manner using just a single set of parameters. To better exploit data volume and diversity we first combine large-scale driving datasets acquired by different types of sensors from diverse scenes and then conduct alignments in three spaces namely data feature and label spaces during the training. As a result M3Net is capable of taming heterogeneous data for training state-of-the-art LiDAR segmentation models. Extensive experiments on twelve LiDAR segmentation datasets verify our effectiveness. Notably using a shared set of parameters M3Net achieves 75.1% 83.1% and 72.4% mIoU scores respectively on the official benchmarks of SemanticKITTI nuScenes and Waymo Open.

ecent progress in video anomaly detection suggests that the features of appearance and motion play crucial roles in distinguishing abnormal patterns from normal ones. However we note that the effect of spatial scales of anomalies is ignored. The fact that many abnormal events occur in limited localized regions and severe background noise interferes with the learning of anomalous changes. Meanwhile most existing methods are limited by coarse-grained modeling approaches which are inadequate for learning highly discriminative features to discriminate subtle differences between small-scale anomalies and normal patterns. To this end this paper address multi-scale video anomaly detection by multi-grained spatio-temporal representation learning. We utilize video continuity to design three proxy tasks to perform feature learning at both coarse-grained and fine-grained levels i.e. continuity judgment discontinuity localization and missing frame estimation. In particular we formulate missing frame estimation as a contrastive learning task in feature space instead of a reconstruction task in RGB space to learn highly discriminative features. Experiments show that our proposed method outperforms state-of-the-art methods on four datasets especially in scenes with small-scale anomalies.

Generalizability in deep neural networks plays a pivotal role in medical image segmentation. However deep learning-based medical image analyses tend to overlook the importance of frequency variance which is critical element for achieving a model that is both modality-agnostic and domain-generalizable. Additionally various models fail to account for the potential information loss that can arise from multi-task learning under deep supervision a factor that can impair the model's representation ability. To address these challenges we propose a Modality-agnostic Domain Generalizable Network (MADGNet) for medical image segmentation which comprises two key components: a Multi-Frequency in Multi-Scale Attention (MFMSA) block and Ensemble Sub-Decoding Module (E-SDM). The MFMSA block refines the process of spatial feature extraction particularly in capturing boundary features by incorporating multi-frequency and multi-scale features thereby offering informative cues for tissue outline and anatomical structures. Moreover we propose E-SDM to mitigate information loss in multi-task learning with deep supervision especially during substantial upsampling from low resolution. We evaluate the segmentation performance of MADGNet across six modalities and fifteen datasets. Through extensive experiments we demonstrate that MADGNet consistently outperforms state-of-the-art models across various modalities showcasing superior segmentation performance. This affirms MADGNet as a robust solution for medical image segmentation that excels in diverse imaging scenarios. Our MADGNet code is available in GitHub Link.

Inspired by the success of general-purpose models in NLP recent studies attempt to unify different vision tasks in the same sequence format and employ autoregressive Transformers for sequence prediction. They apply uni-directional attention to capture sequential dependencies and generate task sequences recursively. However such autoregressive Transformers may not fit vision tasks well as vision task sequences usually lack the sequential dependencies typically observed in natural languages. In this work we design Masked AutoDecoder (MAD) an effective multi-task vision generalist. MAD consists of two core designs. First we develop a parallel decoding framework that introduces bi-directional attention to capture contextual dependencies comprehensively and decode vision task sequences in parallel. Second we design a masked sequence modeling approach that learns rich task contexts by masking and reconstructing task sequences. In this way MAD handles all the tasks by a single network branch and a simple cross-entropy loss with minimal task-specific designs. Extensive experiments demonstrate the great potential of MAD as a new paradigm for unifying various vision tasks. MAD achieves superior performance and inference efficiency compared to autoregressive counterparts while obtaining competitive accuracy with task-specific models. Code will be released at https://github.com/hanqiu-hq/MAD.

In Visual Question Answering (VQA) recognizing and localizing entities pose significant challenges. Pretrained vision-and-language models have addressed this problem by providing a text description as the answer. However in visual scenes with multiple entities textual descriptions struggle to distinguish the entities from the same category effectively. Consequently the VQA dataset is limited by the limitations of text description and cannot adequately cover scenarios involving multiple entities. To address this challenge we introduce a Mask for Align (Mask4Align) method which can determine the entity's position in the given image that best matches the user-input question. This method incorporates colored masks into the image enabling the VQA model to handle discrimination and localization challenges associated with multiple entities. To process an arbitrary number of similar entities Mask4Align is designed hierarchically to discern subtle differences achieving precise localization. Since Mask4Align directly utilizes pre-trained models it does not introduce additional training overhead. Extensive experiments conducted on both the gaze target prediction task dataset and our proposed multi-entity localization dataset showcase the superiority of Mask4Align.

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.

Multi-view photometric stereo (MVPS) recovers a high-fidelity 3D shape of a scene by benefiting from both multi-view stereo and photometric stereo. While photometric stereo boosts detailed shape reconstruction it necessitates recording images under various light conditions for each viewpoint. In particular calibrating the light directions for each view significantly increases the cost of acquiring images. To make MVPS more accessible we introduce a practical and easy-to-implement setup multi-view constrained photometric stereo (MVCPS) where the light directions are unknown but constrained to move together with the camera. Unlike conventional multi-view uncalibrated photometric stereo our constrained setting reduces the ambiguities of surface normal estimates from per-view linear ambiguities to a single and global linear one thereby simplifying the disambiguation process. The proposed method integrates the ambiguous surface normal into neural surface reconstruction (NeuS) to simultaneously resolve the global ambiguity and estimate the detailed 3D shape. Experiments demonstrate that our method estimates accurate shapes under sparse viewpoints using only a few multi-view constrained light sources.

With the rapid development of Multi-modal Large Language Models (MLLMs) a number of diagnostic benchmarks have recently emerged to evaluate the comprehension capabilities of these models. However most benchmarks predominantly assess spatial understanding in the static image tasks while overlooking temporal understanding in the dynamic video tasks. To alleviate this issue we introduce a comprehensive Multi-modal Video understanding Benchmark namely MVBench which covers 20 challenging video tasks that cannot be effectively solved with a single frame. Specifically we first introduce a novel static-to-dynamic method to define these temporal-related tasks. By transforming various static tasks into dynamic ones we enable the systematic generation of video tasks that require a broad spectrum of temporal skills ranging from perception to cognition. Then guided by the task definition we automatically convert public video annotations into multiple-choice QA to evaluate each task. On one hand such a distinct paradigm allows us to build MVBench efficiently without much manual intervention. On the other hand it guarantees evaluation fairness with ground-truth video annotations avoiding the biased scoring of LLMs. Moreover we further develop a robust video MLLM baseline i.e. VideoChat2 by progressive multi-modal training with diverse instruction-tuning data. The extensive results on our MVBench reveal that the existing MLLMs are far from satisfactory in temporal understanding while our VideoChat2 largely surpasses these leading models by over 15% on MVBench.

Multi-target multi-camera tracking is a crucial task that involves identifying and tracking individuals over time using video streams from multiple cameras. This task has practical applications in various fields such as visual surveillance crowd behavior analysis and anomaly detection. However due to the difficulty and cost of collecting and labeling data existing datasets for this task are either synthetically generated or artificially constructed within a controlled camera network setting which limits their ability to model real-world dynamics and generalize to diverse camera configurations. To address this issue we present MTMMC a real-world large-scale dataset that includes long video sequences captured by 16 multi-modal cameras in two different environments - campus and factory - across various time weather and season conditions. This dataset provides a challenging test bed for studying multi-camera tracking under diverse real-world complexities and includes an additional input modality of spatially aligned and temporally synchronized RGB and thermal cameras which enhances the accuracy of multi-camera tracking. MTMMC is a super-set of existing datasets benefiting independent fields such as person detection re-identification and multiple object tracking. We provide baselines and new learning setups on this dataset and set the reference scores for future studies. The datasets models and test server will be made publicly available.