LVNet

Official Code for "Too Many Frames, not all Useful: Efficient Strategies for Long-Form Video QA" paper.

The code will be released soon.

Paper Link

Abstract

Long-form videos that span across wide temporal intervals are highly information- redundant and contain multiple distinct events or entities that are often loosely- related. Therefore, when performing long-form video question answering (LVQA), all information necessary to generate a correct response can often be contained within a small subset of frames. Recent literature explore the use of large language models (LLMs) in LVQA benchmarks, achieving exceptional performance, while relying on vision language models (VLMs) to convert all visual content within videos into natural language. Such VLMs often independently caption a large number of frames uniformly sampled from long videos, which is not efficient and can mostly be redundant. Questioning these decision choices, we explore optimal strategies for key-frame selection and sequence-aware captioning, that can signifi- cantly reduce these redundancies. We propose two novel approaches that improve each of aspects, namely Hierarchical Keyframe Selector and Sequential Visual LLM. Our resulting framework termed LVNet achieves state-of-the-art performance across three benchmark LVQA datasets

Accuracy vs Captions on the EgoSchema Subset

• LVNet shows a SOTA 68.2% accuracy, merely at 12 captions.
• The result highlights the quality of keyframes from the hierarchical keyframe selector.

Hierarchical Keyframe Selector: Structural Overview

• Overall strategy: Generate captions by hierarchical keyframe selector and feed them to the separate LLM to answer the question.
• Temporal Scene Clustering (TSC): Divides the long-video into scenes, enabling per-scene subsampling.
• Coarse Keyframe Detector (CKD): Selects frames best-aligned with keywords relevant to the query.
• Fine Keyframe detector (FKD): Selects frames by refining keyword alignements through a templated visual prompting.

Hierarchical Keyframe Selector: Operational Visualization

• Temporal Scene Clustering (TSC): 900 frames get clustered into scenes and uniformly subsampled within each scene to output around 280 frames.
• Coarse Keyframe Detector (CKD): Coarse Keyframe Detector selects only 32 frames out of them, based on the alignment with keywords which are from options.
• Visual Templating: Coarsely refined keyframes are then ordered according to confidence values, and grouped them into 4 groups of 8 frames each.
• Fine Keyframe Detector (FKD): Selects 12 frames by refining keyword alignments in visual templates.

Experiments: EgoSchema

Experiments: NExT-QA

Experiments: IntentQA

Citation

@inproceedings{Park2024TooMF,
  title={Too Many Frames, not all Useful: Efficient Strategies for Long-Form Video QA},
  author={Jongwoo Park and Kanchana Ranasinghe and Kumara Kahatapitiya and Wonjeong Ryoo and Donghyun Kim and Michael S. Ryoo},
  year={2024}
}