Long-to-Short Video Evidence Reasoning for Grounded Question Answering

Kaiyan Chen, Junbin Xiao, Xun Yang


Abstract
We present LOVER, a  ̲Long to sh ̲Ort  ̲Video  ̲Evidence  ̲Reinforced model for grounded question answering (GQA). LOVER highlights three innovations over existing reinforcement-learning (RL) based video reasoning models: (1) Long-to-short Video Evidence Curriculum Learning, which organizes RL training according to evidence duration and progressively adapts the model from long-range grounding to short-term reasoning; (2) GQA Rewards, which underscore the benefit of IoP reward over IoU for evidence spotting rather than strict temporal span overlap; (3) Adaptive Timestamp Rendering, which adaptively renders timestamps onto video frames using background-aware position and color selection to enhance temporal observability. The three designs are model-agnostic and reciprocal. They effectively improve QA, grounding, and grounded QA performance over different backbones. Notably, LOVER built on Time-R1 achieves new state-of-the-art (SOTA) results among open-source models on popular GQA benchmarks: NExT-GQA and ReXTime. Comprehensive ablation studies further validate the effectiveness of our three innovative components.
Anthology ID:
2026.emnlp-main.253
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
5752–5766
Language:
URL:
https://aclanthology.org/2026.emnlp-main.253/
DOI:
Bibkey:
Cite (ACL):
Kaiyan Chen, Junbin Xiao, and Xun Yang. 2026. Long-to-Short Video Evidence Reasoning for Grounded Question Answering. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 5752–5766, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Long-to-Short Video Evidence Reasoning for Grounded Question Answering (Chen et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.253.pdf