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arXiv 2603.24057cs.CV

超越语义先验:缓解可泛化视觉取证中的优化崩溃

Beyond Semantic Priors: Mitigating Optimization Collapse for Generalizable Visual Forensics

Institute of Information Engineering, Chinese Academy of Sciences(信息工程研究所,中国科学院);School of Cyber Science and Technology, Beihang University(北京航空航天大学信息与科学学院)

Jipeng Liu, Haichao Shi, Siyu Xing, Rong Yin, Xiao-Yu Zhang

AI总结:

本文提出CoRIT模型,通过对比梯度代理和三种无训练策略缓解优化崩溃,提升跨领域和通用伪造检测的泛化能力。

摘要:

尽管视觉-语言模型(VLMs)如CLIP已成为通用深度伪造检测的主流范式,但存在表征断层:其以语义为中心的预训练不适合捕捉超现实合成中的非语义特征。本文识别出一种故障模式,称为优化崩溃,其中使用锐度感知最小化(SAM)训练的检测器在扰动半径超过狭窄阈值后退化为随机猜测。为理论化这一崩溃,我们提出临界优化半径(COR)来量化优化景观的几何稳定性,并利用梯度信号噪声比(GSNR)测量泛化潜力。我们建立定理证明COR随GSNR单调增加,从而揭示SAM优化的几何不稳定性源于降级的内在泛化潜力。这一结果将梯层衰减的GSNR作为检测非语义伪造的优化崩溃根本原因。尽管简单减少扰动半径可使SAM收敛稳定,但仅治标不治本,需增强梯度保真度。基于此见解,我们提出对比区域注入变换器(CoRIT),整合计算高效的对比梯度代理(CGP)与三种无训练策略:区域细化掩码以抑制CGP方差,区域信号注入以保持CGP幅度,以及层次化表征整合以获得更泛化的表征。大量实验表明,CoRIT缓解了优化崩溃,并在跨领域和通用伪造基准上实现了最先进的泛化能力。

英文摘要:

While Vision-Language Models (VLMs) like CLIP have emerged as a dominant paradigm for generalizable deepfake detection, a representational disconnect remains: their semantic-centric pre-training is ill-suited for capturing non-semantic artifacts inherent to hyper-realistic synthesis. In this work, we identify a failure mode termed Optimization Collapse, where detectors trained with Sharpness-Aware Minimization (SAM) degenerate to random guessing on non-semantic forgeries once the perturbation radius exceeds a narrow threshold. To theoretically formalize this collapse, we propose the Critical Optimization Radius (COR) to quantify the geometric stability of the optimization landscape, and leverage the Gradient Signal-to-Noise Ratio (GSNR) to measure generalization potential. We establish a theorem proving that COR increases monotonically with GSNR, thereby revealing that the geometric instability of SAM optimization originates from degraded intrinsic generalization potential. This result identifies the layer-wise attenuation of GSNR as the root cause of Optimization Collapse in detecting non-semantic forgeries. Although naively reducing perturbation radius yields stable convergence under SAM, it merely treats the symptom without mitigating the intrinsic generalization degradation, necessitating enhanced gradient fidelity. Building on this insight, we propose the Contrastive Regional Injection Transformer (CoRIT), which integrates a computationally efficient Contrastive Gradient Proxy (CGP) with three training-free strategies: Region Refinement Mask to suppress CGP variance, Regional Signal Injection to preserve CGP magnitude, and Hierarchical Representation Integration to attain more generalizable representations. Extensive experiments demonstrate that CoRIT mitigates optimization collapse and achieves state-of-the-art generalization across cross-domain and universal forgery benchmarks.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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