CVPR 2024 Papers

Retrieval tasks play central roles in real-world machine learning systems such as search engines recommender systems and retrieval-augmented generation (RAG). Achieving decent performance in these tasks often requires fine-tuning various pre-trained models on specific datasets and selecting the best candidate a process that can be both time and resource-consuming. To tackle the problem we introduce a novel and efficient method called RetMMD that leverages Maximum Mean Discrepancy (MMD) and kernel methods to assess the transferability of pretrained models in retrieval tasks. RetMMD is calculated on pretrained model and target dataset without any fine-tuning involved. Specifically given some query we quantify the distribution discrepancy between relevant and irrelevant document embeddings by estimating the similarities within their mappings in the fine-tuned embedding space through kernel method. This discrepancy is averaged over multiple queries taking into account the distribution characteristics of the target dataset. Experiments suggest that the proposed metric calculated on pre-trained models closely aligns with retrieval performance post-fine-tuning. The observation holds across a variety of datasets including image text and multi-modal domains indicating the potential of using MMD and kernel methods for transfer learning evaluation in retrieval scenarios. In addition we also design a way of evaluating dataset transferability for retrieval tasks with experimental results demonstrating the effectiveness of the proposed approach.

Multi-task learning for dense prediction has emerged as a pivotal area in computer vision enabling simultaneous processing of diverse yet interrelated pixel-wise prediction tasks. However the substantial computational demands of state-of-the-art (SoTA) models often limit their widespread deployment. This paper addresses this challenge by introducing network binarization to compress resource-intensive multi-task dense predictors. Specifically our goal is to significantly accelerate multi-task dense prediction models via Binary Neural Networks (BNNs) while maintaining and even improving model performance at the same time. To reach this goal we propose a Binary Multi-task Dense Predictor Bi-MTDP and several variants of \bimtdp in which a multi-task dense predictor is constructed via specified binarized modules. Our systematical analysis of this predictor reveals that performance drop from binarization is primarily caused by severe information degradation. To address this issue we introduce a deep information bottleneck layer that enforces representations for downstream tasks satisfying Gaussian distribution in forward propagation. Moreover we introduce a knowledge distillation mechanism to correct the direction of information flow in backward propagation. Intriguingly one variant of Bi-MTDP outperforms full-precision (FP) multi-task dense prediction SoTAs ARTC (CNN-based) and InvPT (ViT-based). This result indicates that Bi-MTDP is not merely a naive trade-off between performance and efficiency but is rather a benefit of the redundant information flow thanks to the multi-task architecture.

We present a novel method for efficiently producing semi-dense matches across images. Previous detector-free matcher LoFTR has shown remarkable matching capability in handling large-viewpoint change and texture-poor scenarios but suffers from low efficiency. We revisit its design choices and derive multiple improvements for both efficiency and accuracy. One key observation is that performing the transformer over the entire feature map is redundant due to shared local information therefore we propose an aggregated attention mechanism with adaptive token selection for efficiency. Furthermore we find spatial variance exists in LoFTR's fine correlation module which is adverse to matching accuracy. A novel two-stage correlation layer is proposed to achieve accurate subpixel correspondences for accuracy improvement. Our efficiency optimized model is ~ 2.5xfaster than LoFTR which can even surpass state-of-the-art efficient sparse matching pipeline SuperPoint + LightGlue. Moreover extensive experiments show that our method can achieve higher accuracy compared with competitive semi-dense matchers with considerable efficiency benefits. This opens up exciting prospects for large-scale or latency-sensitive applications such as image retrieval and 3D reconstruction. Project page: https://zju3dv.github.io/efficientloftr/.

In the context of pose-invariant object recognition and retrieval we demonstrate that it is possible to achieve significant improvements in performance if both the category-based and the object-identity-based embeddings are learned simultaneously during training. In hindsight that sounds intuitive because learning about the categories is more fundamental than learning about the individual objects that correspond to those categories. However to the best of what we know no prior work in pose invariant learning has demonstrated this effect. This paper presents an attention-based dual-encoder architecture with specially designed loss functions that optimize the inter- and intra-class distances simultaneously in two different embedding spaces one for the category embeddings and the other for the object level embeddings. The loss functions we have proposed are pose-invariant ranking losses that are designed to minimize the intra-class distances and maximize the inter-class distances in the dual representation spaces. We demonstrate the power of our approach with three challenging multi-view datasets ModelNet-40 ObjectPI and FG3D. With our dual approach for single view object recognition we outperform the previous best by 20.0% on ModelNet40 2.0% on ObjectPI and 46.5% on FG3D. On the other hand for single-view object retrieval we outperform the previous best by 33.7% on ModelNet40 18.8% on ObjectPI and 56.9% on FG3D.

There has been significant attention to the research on dense video captioning which aims to automatically localize and caption all events within untrimmed video. Several studies introduce methods by designing dense video captioning as a multitasking problem of event localization and event captioning to consider inter-task relations. However addressing both tasks using only visual input is challenging due to the lack of semantic content. In this study we address this by proposing a novel framework inspired by the cognitive information processing of humans. Our model utilizes external memory to incorporate prior knowledge. The memory retrieval method is proposed with cross-modal video-to-text matching. To effectively incorporate retrieved text features the versatile encoder and the decoder with visual and textual cross-attention modules are designed. Comparative experiments have been conducted to show the effectiveness of the proposed method on ActivityNet Captions and YouCook2 datasets. Experimental results show promising performance of our model without extensive pretraining from a large video dataset. Our code is available at https://github.com/ailab-kyunghee/CM2_DVC.

Concealed Object Detection (COD) aims to identify objects visually embedded in their background. Existing COD datasets and methods predominantly focus on animals or humans ignoring the agricultural domain which often contains numerous small and concealed crops with severe occlusions. In this paper we introduce Concealed Crop Detection (CCD) which extends classic COD to agricultural domains. Experimental study shows that unimodal data provides insufficient information for CCD. To address this gap we first collect a large-scale RGB-D dataset ACOD-12K containing high-resolution crop images and depth maps. Then we propose a foundational framework named Recurrent Iterative Segmentation Network (RISNet). To tackle the challenge of dense objects we employ multi-scale receptive fields to capture objects of varying sizes thus enhancing the detection performance for dense objects. By fusing depth features our method can acquire spatial information about concealed objects to mitigate disturbances caused by intricate backgrounds and occlusions. Furthermore our model adopts a multi-stage iterative approach using predictions from each stage as gate attention to reinforce position information thereby improving the detection accuracy for small objects. Extensive experimental results demonstrate that our RISNet achieves new state-of-the-art performance on both newly proposed CCD and classic COD tasks. All resources will be available at https://github.com/Kki2Eve/RISNet.

Recent approaches to point tracking are able to recover the trajectory of any scene point through a large portion of a video despite the presence of occlusions. They are however too slow in practice to track every point observed in a single frame in a reasonable amount of time. This paper introduces DOT a novel simple and efficient method for solving this problem. It first extracts a small set of tracks from key regions at motion boundaries using an off-the-shelf point tracking algorithm. Given source and target frames DOT then computes rough initial estimates of a dense flow field and visibility mask through nearest-neighbor interpolation before refining them using a learnable optical flow estimator that explicitly handles occlusions and can be trained on synthetic data with ground-truth correspondences. We show that DOT is significantly more accurate than current optical flow techniques outperforms sophisticated "universal" trackers like OmniMotion and is on par with or better than the best point tracking algorithms like CoTracker while being at least two orders of magnitude faster. Quantitative and qualitative experiments with synthetic and real videos validate the promise of the proposed approach. Code data and videos showcasing the capabilities of our approach are available in the project webpage: https://16lemoing.github.io/dot .

We present Dive Into the Boundaries (DIBS) a novel pretraining framework for dense video captioning (DVC) that elaborates on improving the quality of the generated event captions and their associated pseudo event boundaries from unlabeled videos. By leveraging the capabilities of diverse large language models (LLMs) we generate rich DVC-oriented caption candidates and optimize the corresponding pseudo boundaries under several meticulously designed objectives considering diversity event-centricity temporal ordering and coherence. Moreover we further introduce a novel online boundary refinement strategy that iteratively improves the quality of pseudo boundaries during training. Comprehensive experiments have been conducted to examine the effectiveness of the proposed technique components. By leveraging a substantial amount of unlabeled video data such as HowTo100M we achieve a remarkable advancement on standard DVC datasets like YouCook2 and ActivityNet. We outperform the previous state-of-the-art Vid2Seq across a majority of metrics achieving this with just 0.4% of the unlabeled video data used for pre-training by Vid2Seq.

Composed video retrieval (CoVR) is a challenging prob- lem in computer vision which has recently highlighted the in- tegration of modification text with visual queries for more so- phisticated video search in large databases. Existing works predominantly rely on visual queries combined with modi- fication text to distinguish relevant videos. However such a strategy struggles to fully preserve the rich query-specific context in retrieved target videos and only represents the target video using visual embedding. We introduce a novel CoVR framework that leverages detailed language descrip- tions to explicitly encode query-specific contextual informa- tion and learns discriminative embeddings of vision only text only and vision-text for better alignment to accurately retrieve matched target videos. Our proposed framework can be flexibly employed for both composed video (CoVR) and image (CoIR) retrieval tasks. Experiments on three datasets show that our approach obtains state-of-the-art per- formance for both CovR and zero-shot CoIR tasks achiev- ing gains as high as around 7% in terms of recall@K=1 score. Our code detailed language descriptions for WebViD- CoVR dataset are available at https://github.com/ OmkarThawakar/composed-video-retrieval.

Recently the rise of query-based Transformer decoders is reshaping camera-based 3D object detection. These query-based decoders are surpassing the traditional dense BEV (Bird's Eye View)-based methods. However we argue that dense BEV frameworks remain important due to their outstanding abilities in depth estimation and object localization depicting 3D scenes accurately and comprehensively. This paper aims to address the drawbacks of the existing dense BEV-based 3D object detectors by introducing our proposed enhanced components including a CRF-modulated depth estimation module enforcing object-level consistencies a long-term temporal aggregation module with extended receptive fields and a two-stage object decoder combining perspective techniques with CRF-modulated depth embedding. These enhancements lead to a "modernized" dense BEV framework dubbed BEVNeXt. On the nuScenes benchmark BEVNeXt outperforms both BEV-based and query-based frameworks under various settings achieving a state-of-the-art result of 64.2 NDS on the nuScenes test set.

Many reinforcement learning environments (e.g. Minecraft) provide only sparse rewards that indicate task completion or failure with binary values. The challenge in exploration efficiency in such environments makes it difficult for reinforcement-learning-based agents to learn complex tasks. To address this this paper introduces an advanced learning system named Auto MC-Reward that leverages Large Language Models (LLMs) to automatically design dense reward functions thereby enhancing the learning efficiency. Auto MC-Reward consists of three important components: Reward Designer Reward Critic and Trajectory Analyzer. Given the environment information and task descriptions the Reward Designer first design the reward function by coding an executable Python function with predefined observation inputs. Then our Reward Critic will be responsible for verifying the code checking whether the code is self-consistent and free of syntax and semantic errors. Further the Trajectory Analyzer summarizes possible failure causes and provides refinement suggestions according to collected trajectories. In the next round Reward Designer will further refine and iterate the dense reward function based on feedback. Experiments demonstrate a significant improvement in the success rate and learning efficiency of our agents in complex tasks in Minecraft such as obtaining diamond with the efficient ability to avoid lava and efficiently explore trees and animals that are sparse in the plains biome.

In various domains such as surveillance and smart retail pedestrian retrieval centering on person re-identification (Re-ID) plays a pivotal role. Existing Re-ID methodologies often overlook subtle internal attribute variations which are crucial for accurately identifying individuals with changing appearances. In response our paper introduces the Attribute-Guided Pedestrian Retrieval (AGPR) task focusing on integrating specified attributes with query images to refine retrieval results. Although there has been progress in attribute-driven image retrieval there remains a notable gap in effectively blending robust Re-ID models with intra-class attribute variations. To bridge this gap we present the Attribute-Guided Transformer-based Pedestrian Retrieval (ATPR) framework. ATPR adeptly merges global ID recognition with local attribute learning ensuring a cohesive linkage between the two. Furthermore to effectively handle the complexity of attribute interconnectivity ATPR organizes attributes into distinct groups and applies both inter-group correlation and intra-group decorrelation regularizations. Our extensive experiments on a newly established benchmark using the RAP dataset demonstrate the effectiveness of ATPR within the AGPR paradigm.