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Unleashing Hour-Scale Video Training for Long Video-Language Understanding

NeurIPS 2025 · Video › Video-language understanding · approach: Long video understanding · 3 citations (OpenAlex)

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Introduces VideoMarathon, a 9.7K-hour synthetic hour-long video instruction dataset (3.3M QA over 22 tasks), and Hour-LLaVA, a Video-LMM that caches full 1-FPS video tokens in a memory repository and uses a MemAug cross-attention module to recover question-relevant detail from compressed tokens.

Problem

Hour-long video-language training is underexplored because well-annotated long-video instruction data is scarce, and existing Video-LMMs either sparsely sample frames (losing information) or process dense frames at prohibitive token cost.

Approach

Store full 1-FPS video tokens in a memory repository, feed only a compressed (~1/16 overall) set of decayed tokens to the LLM, and use learnable MemAug transformer blocks to re-inject question-relevant spatiotemporal details from the full cache, combined with a hierarchical (clip/event/global) synthetic captioning and QA pipeline for long videos.

Key results

Measured effects reported in the paper

What was changedWhereMeasuredEffect
Add Hour-LLaVA long-video training and memory augmentationLLaVA-Video-3B · LongVideoBenchM-Avg: 55.2 -> 57.8Helped
Add Hour-LLaVA long-video training and memory augmentationLLaVA-Video-7B · LVBenchAvg: 42.2 -> 45.6Helped
Use random spatial forgetting at 1/4 compression instead of no token compression (ablation)LLaVA-OV-SI-3B · MMStarscore: 52.8 -> 51.9Hurt
Use random spatial forgetting at 1/4 compression instead of no token compression (ablation)LLaVA-OV-SI-3B · Sci.QAscore: 84.7 -> 84.5Hurt
Use uniform spatial forgetting at 1/4 compression instead of no token compression (ablation)LLaVA-OV-SI-3B · MMStarscore: 52.8 -> 51.5Hurt
Replace random temporal forgetting with uniform temporal forgetting (ablation)Hour-LLaVA-3B · LongVideoBenchM-Avg: 53.2 -> 54.0Helped
Add MemAug to uniform temporal compression (ablation)Hour-LLaVA-3B · LongVideoBenchM-Avg: +1.9Helped
Add MemAug to uniform temporal compression (ablation)Hour-LLaVA-3B · LVBenchAvg: +2.3Helped
Add 2 MemAug blocks instead of 1 (ablation)Hour-LLaVA-3B · TempCompassM-Avg: 59.4 -> 59.8Helped
Remove 1D structured RoPE from MemAug (ablation)Hour-LLaVA-3B · Video-MME (Temporal Reasoning)score: 46.3 -> 35.6 (-10.7)Hurt

Surprising findings

Limitations

Experimental setup

Datasets: VideoMarathon LLaVA-OneVision single-image data LLaVA-Video-178K Panda-70M Ego4D ActivityNet YouCook2 MovieChat-1K

Benchmarks: TempCompass LongVideoBench Video-MME LVBench MLVU-Dev MMStar ScienceQA RealWorldQA

Metrics: accuracy M-Avg average score (GPT-4-Turbo rating 2-10) human hallucination score (1-10) yes/no bias (Pct. Diff, FP Ratio)

Baselines: LLaVA-Video-3B LLaVA-Video-7B LLaVA-OV-SI Qwen2.5-VL-3B Qwen2-VL-7B Apollo LongVU LongVILA Kangaroo Video-XL

Builds on: LLaVA-Video LLaVA-OneVision SigLIP Qwen2.5

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