@inproceedings{chen-etal-2026-long,
title = "Long-to-Short Video Evidence Reasoning for Grounded Question Answering",
author = "Chen, Kaiyan and
Xiao, Junbin and
Yang, Xun",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-main.253/",
pages = "5752--5766",
ISBN = "979-8-89176-459-0",
abstract = "We present $\textbf{LOVER}$, a $\underline{L}$ong to sh$\underline{O}$rt $\underline{V}$ideo $\underline{E}$vidence $\underline{R}$einforced model for grounded question answering (GQA). $\textbf{LOVER}$ highlights three innovations over existing reinforcement-learning (RL) based video reasoning models: (1) $\textbf{Long-to-short Video Evidence Curriculum Learning}$, which organizes RL training according to evidence duration and progressively adapts the model from long-range grounding to short-term reasoning; (2) $\textbf{GQA Rewards}$, which underscore the benefit of IoP reward over IoU for evidence spotting rather than strict temporal span overlap; (3) $\textbf{Adaptive Timestamp Rendering}$, 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, $\textbf{LOVER}$ 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."
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<abstract>We present LOVER, a \underlineLong to sh\underlineOrt \underlineVideo \underlineEvidence \underlineReinforced 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.</abstract>
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%0 Conference Proceedings
%T Long-to-Short Video Evidence Reasoning for Grounded Question Answering
%A Chen, Kaiyan
%A Xiao, Junbin
%A Yang, Xun
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-459-0
%F chen-etal-2026-long
%X We present LOVER, a \underlineLong to sh\underlineOrt \underlineVideo \underlineEvidence \underlineReinforced 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.
%U https://aclanthology.org/2026.emnlp-main.253/
%P 5752-5766
Markdown (Informal)
[Long-to-Short Video Evidence Reasoning for Grounded Question Answering](https://aclanthology.org/2026.emnlp-main.253/) (Chen et al., EMNLP 2026)
ACL