Video question answering (VideoQA) aims to answer natural language questions according to the given videos. Although existing models perform well in the factoid VideoQA task, they still face challenges in deep video understanding (DVU) task, which focuses on story videos. Compared to factoid videos, the most significant feature of story videos is storylines, which are composed of complex interactions and long-range evolvement of core story topics including characters, actions and locations. Understanding these topics requires models to possess DVU capability. However, existing DVU datasets rarely organize questions according to these story topics, making them difficult to comprehensively assess VideoQA models' DVU capability of complex storylines. Additionally, the question quantity and video length of these dataset are limited by high labor costs of handcrafted dataset building method. In this paper, we devise a large language model based multi-agent collaboration framework, StoryMind, to automatically generate a new large-scale DVU dataset. The dataset, FriendsQA, derived from the renowned sitcom Friends with an average episode length of 1,358 seconds, contains 44.6K questions evenly distributed across 14 fine-grained topics. Finally, We conduct comprehensive experiments on 10 state-of-the-art VideoQA models using the FriendsQA dataset.

Who, What and Where (3W)are the three core elements of storytelling, and accurately identifying the 3W semantics is critical to understanding the story in a video. This paper studies the 3W composite-semantics video Instance Search (INS) problem, which aims to find video shots about a specific person doing a concrete action in a particular location. The popular Complete-Decomposition (CD) methods divide a composite-semantics query into multiple single-semantics queries, which are likely to yield inaccurate or incomplete retrieval results due to neglecting important semantic correlations. Recent Non-Decomposition (ND) methods utilize Vision Language Model (VLM) to directly measure the similarity between textual query and video content. However, the accuracy is limited by VLM's immature capability to recognize fine-grained objects. To address the above challenges, we propose a video structure-aware Partial-Decomposition (PD) method. Its core idea is to partially decompose the 3W INS problem into three semantic-correlated 2W INS problems i.e., person-action INS, action-location INS, and location-person INS. Thereafter, we respectively model the correlations between pairs of semantics at frames, shots and scenes of story videos. With the help of the spatial consistency and temporal continuity contained in the unique hierarchical structure of story videos, we can finally obtain identity-matching, logic-consistent, and content-coherent 3W INS results. To validate the effectiveness of the proposed method, we specifically build three large-scale 3W INS datasets based on three TV series Eastenders, Friends and The Big Bang Theory, totally comprising over 670K video shots spanning 700 hours. Extensive experiments show that the proposed PD method surpasses the current state-of-the-art CD and ND methods for 3W INS in story videos.

Deep video understanding (DVU) is often considered a challenge due to the aim of interpreting a video with storyline, which is designed to solve two levels of problems: predicting the human interaction in scene-level and identifying the relationship between two entities in movie-level. Based on our understanding of the movie characteristics and analysis of DVU tasks, in this paper, we propose a four-stage method to solve the task, which includes video structuring, shot based instance search, interaction & relation prediction and shot-scene summary & Question Answering (QA) with ChatGPT. In these four stages, shot based instance search allows accurate identification and tracking of characters at an appropriate video granularity. Using ChatGPT in QA, on the one hand, can narrow the answer space, on the other hand, with the help of the powerful text understanding ability, ChatGPT can help us answer the questions by giving background knowledge. We rank first in movie-level group 2 and scene-level group 1, second in movie-level group 1 and scene-level group 2 in ACM MM 2023 Grand Challenge.