MR. Video: "MapReduce" is the Principle for Long Video Understanding
Authors: name: Ziqi Pang; name: Yu-Xiong Wang
Published: 2025-04-22 17:59:41

Abstract: We propose MR. Video, an agentic long video understanding framework that
demonstrates the simple yet effective MapReduce principle for processing long
videos: (1) Map: independently and densely perceiving short video clips, and
(2) Reduce: jointly aggregating information from all clips. Compared with
sequence-to-sequence vision-language models (VLMs), MR. Video performs detailed
short video perception without being limited by context length. Compared with
existing video agents that typically rely on sequential key segment selection,
the Map operation enables simpler and more scalable sequence parallel
perception of short video segments. Its Reduce step allows for more
comprehensive context aggregation and reasoning, surpassing explicit key
segment retrieval. This MapReduce principle is applicable to both VLMs and
video agents, and we use LLM agents to validate its effectiveness.
  In practice, MR. Video employs two MapReduce stages: (A) Captioning:
generating captions for short video clips (map), then standardizing repeated
characters and objects into shared names (reduce); (B) Analysis: for each user
question, analyzing relevant information from individual short videos (map),
and integrating them into a final answer (reduce). MR. Video achieves over 10%
accuracy improvement on the challenging LVBench compared to state-of-the-art
VLMs and video agents.
  Code is available at: https://github.com/ziqipang/MR-Video