VideoNav: Cost-Aware Index Navigation for Long Video Understanding

Yulong Hui, Yuchen Li, Rui Kong, Xinran Chen, Jinman Zhao, Dawei Yin, Huanchen Zhang


Abstract
The rising demand for long-video understanding presents significant challenges due to massive information and complex temporal dependencies. Direct processing with Large Visual Language Models (VLMs) incurs high computational costs and risks information loss due to frame sampling. Meanwhile, existing agent-based methods often struggle with fragmented contexts and the high overhead of iterative processing. Therefore, we propose VideoNav, which introduces a new paradigm of index-centric navigation, reformulating video understanding as cost-aware structured query processing. VideoNav decouples heavy perception from online reasoning, including offline index construction and online adaptive navigation. In the offline phase, we transform unstructured video data into a structured, multi-granular index tree. During the online phase, the framework executes a top-down, coarse-to-fine navigating strategy. Leveraging the LLM agents, it efficiently locates relevant information and answers the query with navigating guidance, multi-level navigation, dual-path routing and visual inspection. Crucially, this adaptive mechanism enables early termination when high-level information suffices, minimizing redundant computation. Extensive experiments across different benchmarks demonstrate the effectiveness of our framework. VideoNav achieves decent accuracy while delivering 2.5x-5.7x cost savings and a 2.9x-5.8x speedup.
Anthology ID:
2026.findings-emnlp.1843
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
39346–39362
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1843/
DOI:
Bibkey:
Cite (ACL):
Yulong Hui, Yuchen Li, Rui Kong, Xinran Chen, Jinman Zhao, Dawei Yin, and Huanchen Zhang. 2026. VideoNav: Cost-Aware Index Navigation for Long Video Understanding. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 39346–39362, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
VideoNav: Cost-Aware Index Navigation for Long Video Understanding (Hui et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1843.pdf