iFinder: Structured Zero-Shot Vision-Based LLM Grounding for Dash-Cam Video Reasoning

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Hauptverfasser: Yao, Manyi, Zhuang, Bingbing, Garg, Sparsh, Roy-Chowdhury, Amit, Shelton, Christian, Chandraker, Manmohan, Aich, Abhishek
Format: Preprint
Veröffentlicht: 2025
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author Yao, Manyi
Zhuang, Bingbing
Garg, Sparsh
Roy-Chowdhury, Amit
Shelton, Christian
Chandraker, Manmohan
Aich, Abhishek
author_facet Yao, Manyi
Zhuang, Bingbing
Garg, Sparsh
Roy-Chowdhury, Amit
Shelton, Christian
Chandraker, Manmohan
Aich, Abhishek
contents Grounding large language models (LLMs) in domain-specific tasks like post-hoc dash-cam driving video analysis is challenging due to their general-purpose training and lack of structured inductive biases. As vision is often the sole modality available for such analysis (i.e., no LiDAR, GPS, etc.), existing video-based vision-language models (V-VLMs) struggle with spatial reasoning, causal inference, and explainability of events in the input video. To this end, we introduce iFinder, a structured semantic grounding framework that decouples perception from reasoning by translating dash-cam videos into a hierarchical, interpretable data structure for LLMs. iFinder operates as a modular, training-free pipeline that employs pretrained vision models to extract critical cues -- object pose, lane positions, and object trajectories -- which are hierarchically organized into frame- and video-level structures. Combined with a three-block prompting strategy, it enables step-wise, grounded reasoning for the LLM to refine a peer V-VLM's outputs and provide accurate reasoning. Evaluations on four public dash-cam video benchmarks show that iFinder's proposed grounding with domain-specific cues, especially object orientation and global context, significantly outperforms end-to-end V-VLMs on four zero-shot driving benchmarks, with up to 39% gains in accident reasoning accuracy. By grounding LLMs with driving domain-specific representations, iFinder offers a zero-shot, interpretable, and reliable alternative to end-to-end V-VLMs for post-hoc driving video understanding.
format Preprint
id arxiv_https___arxiv_org_abs_2509_19552
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle iFinder: Structured Zero-Shot Vision-Based LLM Grounding for Dash-Cam Video Reasoning
Yao, Manyi
Zhuang, Bingbing
Garg, Sparsh
Roy-Chowdhury, Amit
Shelton, Christian
Chandraker, Manmohan
Aich, Abhishek
Computer Vision and Pattern Recognition
Grounding large language models (LLMs) in domain-specific tasks like post-hoc dash-cam driving video analysis is challenging due to their general-purpose training and lack of structured inductive biases. As vision is often the sole modality available for such analysis (i.e., no LiDAR, GPS, etc.), existing video-based vision-language models (V-VLMs) struggle with spatial reasoning, causal inference, and explainability of events in the input video. To this end, we introduce iFinder, a structured semantic grounding framework that decouples perception from reasoning by translating dash-cam videos into a hierarchical, interpretable data structure for LLMs. iFinder operates as a modular, training-free pipeline that employs pretrained vision models to extract critical cues -- object pose, lane positions, and object trajectories -- which are hierarchically organized into frame- and video-level structures. Combined with a three-block prompting strategy, it enables step-wise, grounded reasoning for the LLM to refine a peer V-VLM's outputs and provide accurate reasoning. Evaluations on four public dash-cam video benchmarks show that iFinder's proposed grounding with domain-specific cues, especially object orientation and global context, significantly outperforms end-to-end V-VLMs on four zero-shot driving benchmarks, with up to 39% gains in accident reasoning accuracy. By grounding LLMs with driving domain-specific representations, iFinder offers a zero-shot, interpretable, and reliable alternative to end-to-end V-VLMs for post-hoc driving video understanding.
title iFinder: Structured Zero-Shot Vision-Based LLM Grounding for Dash-Cam Video Reasoning
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2509.19552