CLIP, widely used in multimodal learning, excels due to its large-scale image-text pretraining. However, applying CLIP-like architectures to skeleton-based action representation learning presents challenges due to the incompatible non-visual data structure and the limited scale of skeleton datasets, which hinder robust generalization. To address these issues, we propose SKL-CLIP, a framework that incorporates Supervised Self-Contrastive Learning to mitigate overfitting and enhance transferable representation learning, Knowledge Distillation from the textual encoder of pretrained CLIP models to preserve generalization while adapting to skeleton-text scenarios, and Multi-Domain Parallel Training to leverage diverse support datasets, improving cross-dataset and zero-shot recognition. Extensive experiments on NTU and PKU datasets demonstrate that SKL-CLIP significantly advances skeleton-based action representation, achieving state-of-the-art performance across fully-supervised, cross-data unsupervised domain adaptation, and zero-shot tasks.

The performance of current Vision-Language Tracking (VLT) models is constrained by the limited diversity and quantity of labeled data. Compared to constructing large-scale datasets, data augmentation offers a more cost-saving strategy for VLT by synthesizing new samples from existing data, rather than generating them from scratch. However, conventional techniques like rotation and flipping may disrupt scene composition, causing conflicts between visual layouts and textual annotations. Recent advances in generative models have inspired the use of synthetic videos for data augmentation. Yet, existing approaches fail to address the core concerns of data augmentation in VLT (shown in Fig. 1)-target location accuracy, text-video consistency, and video content coherency. To bridge the gap, we propose Gen4Track, a tuning-free data augmentation framework that leverages the self-correcting mechanism to dynamically generate high-quality video data with annotations. Our approach involves (1) optimizing the attention calculations in a frozen text-to-image diffusion model to synthesize coherent videos that satisfy specific conditions (e.g., spatial location, category, color, and style), and (2) implementing a self-correcting mechanism based on a Large Language Model (LLM) to improve text-video consistency. During video augmentation, we propose content-coherent self-attention and location-enhanced cross-attention mechanisms, ensuring that image-level editings are accurately and coherently propagated throughout the video. Then, with the goal of maximizing text-video consistency, we iteratively refine the augmentation instruction with our designed self-correcting mechanism for a more aligned video. Extensive experiments validate that Gen4Track significantly boosts the performance of SOTA VLT models (achieving improvements of up to 3.2% in SUC and 3.5% in PRE), opening a new chapter of training Vision-Language trackers with synthetic videos rather than manually annotated data.

Single object tracking aims to locate one specific target in video sequences, given its initial state. Classical trackers rely solely on visual cues, restricting their ability to handle challenges such as appearance variations, ambiguity, and distractions. Hence, Vision-Language Tracking (VLT) has emerged as a promising approach, incorporating language descriptions to directly provide high-level semantics and enhance tracking performance. However, current Vision-Language (VL) trackers have not fully exploited the power of multi-modal learning, as they suffer from limitations such as heavily relying on off-the-shelf backbones for feature extraction, ineffective asynchronous fusion designs, and the absence of VL-related loss functions for optimizing multi-modal representation. Consequently, we present a novel tracker that progressively explores target-centric semantics for VLT. Specifically, we propose the first Synchronous Learning Backbone (SLB) for VLT, which consists of two novel modules: the Target Enhance Module (TEM) and the Semantic-Aware Module (SAM). These modules together ensure the multi-modal feature extraction and interaction at the same pace, facilitating the tracker to synchronously perceive target-related semantics from both visual and textual modalities. Moreover, we devise the dense matching loss to further strengthen multi-modal representation learning. Extensive experiments on VLT datasets demonstrate the superiority and effectiveness of our methods.

Skeleton-based Action Recognition (SAR) is widely recognized for its robustness and efficiency in human action analysis, but its performance in cross-dataset tasks has been limited due to domain shifts between different datasets. To address this challenge, current methods typically approach cross-dataset SAR as an Unsupervised Domain Adaptation (UDA) task, which is tackled using domain adaptation or self-supervised learning strategies. In this article, we propose a Dual-Domain Triple Contrast (D2TC) framework for cross-dataset SAR under the UDA setting. Unlike existing UDA methods that either focus on a single strategy or superficially combine strategies, our D2TC leverages contrastive learning to integrate both strategies into a unified framework. It performs three types of contrastive learning: Self-Supervised Contrastive Learning, Supervised Contrastive Learning, and UDA with Contrastive Learning, across both source and target domains. The triple contrasts go beyond mere summation, effectively bridging the domain gap and enhancing the model’s representational capacity. Additionally, we introduce multi-modal ensemble contrast and extreme skeleton augmentation methods to further enhance the skeleton-based representation learning. Extensive experiments on six cross-dataset settings validate the superiority of our D2TC framework over state-of-the-art methods, demonstrating its effectiveness in reducing domain discrepancies and improving cross-dataset SAR performance. The codes are available on https://github.com/KennCoder7/DualDomainTripleContrast .

Vision-Language Tracking (VLT) requires locating a specific target in video sequences, given a natural language prompt and an initial object box. Despite recent advancements, existing approaches heavily rely on expensive and time-consuming human annotations. To mitigate this limitation, directly generating pseudo labels from raw videos seems to be a straightforward solution; however, it inevitably introduces undesirable noise during the training process. Moreover, we insist that an efficient tracker should excel in tracking the target, regardless of the temporal direction. Building upon these insights, we propose the pioneering semi-supervised learning scheme for VLT task, representing a crucial step towards reducing the dependency on high-quality yet costly labeled data. Specifically, drawing inspiration from the natural attributes of a video (i.e., space, time, and semantics), our approach progressively leverages inherent consistencies from these aspects: (1) Spatially, each frame and any object cropped from it naturally form an image-bbox (bounding box) pair for self-training; (2) Temporally, bidirectional tracking trajectories should exhibit minimal differences; (3) Semantically, the correlation between visual and textual features is expected to remain consistent. Furthermore, the framework is validated with a simple yet effective tracker we devised, named ATTracker (Asymmetrical Transformer Tracker). It modifies the self-attention operation in an asymmetrical way, striving to enhance target-related features while suppressing noise. Extensive experiments confirm that our ATTracker serves as a robust baseline, outperforming fully supervised base trackers. By unveiling the potential of learning with limited annotations, this study aims to attract attention and pave the way for Semi-supervised Vision-Language Tracking (SS-VLT).

Event-based Social Network (EBSN) is a special online social network that not only provides users with a convenient virtual platform to communicate, but also helps them to participate in offline face-to-face social activities on a group basis. This paper studies the group popularity prediction problem in EBSN which is important for online advertising and event recommendation. Firstly, we construct the EBSN temporal network model with a timeline involved and propose a novel definition of group popularity in EBSN. Then on the basis of the above, we extract corresponding key features from four aspects: inherent group characteristics (i.e., founder, created time), historical popularity, the sentiment of users towards events as an internal factor, and the initiative of newly added users as an external factor. Combining these four features, we propose a group popularity prediction algorithm in EBSN based on an improved self-excited Hawkes Process: EBSN-Hawkes Process Algorithm (EHP). Experiments conducted by real EBSN datasets demonstrate that the proposed EHP algorithm has better prediction results than other comparative algorithms. We also conclude that the external dynamic feature plays a more important role than the internal sentiment feature by the ablation study.