ViSMaP: Unsupervised Hour-long Video Summarisation by Meta-Prompting
Authors: name: Jian Hu, name: Dimitrios Korkinof, name: Shaogang Gong, name: Mariano Beguerisse-Diaz

We introduce ViSMap: Unsupervised Video Summarisation by Meta Prompting, a
system to summarise hour long videos with no-supervision. Most existing video
understanding models work well on short videos of pre-segmented events, yet
they struggle to summarise longer videos where relevant events are sparsely
distributed and not pre-segmented. Moreover, long-form video understanding
often relies on supervised hierarchical training that needs extensive
annotations which are costly, slow and prone to inconsistency. With ViSMaP we
bridge the gap between short videos (where annotated data is plentiful) and
long ones (where it's not). We rely on LLMs to create optimised
pseudo-summaries of long videos using segment descriptions from short ones.
These pseudo-summaries are used as training data for a model that generates
long-form video summaries, bypassing the need for expensive annotations of long
videos. Specifically, we adopt a meta-prompting strategy to iteratively
generate and refine creating pseudo-summaries of long videos. The strategy
leverages short clip descriptions obtained from a supervised short video model
to guide the summary. Each iteration uses three LLMs working in sequence: one
to generate the pseudo-summary from clip descriptions, another to evaluate it,
and a third to optimise the prompt of the generator. This iteration is
necessary because the quality of the pseudo-summaries is highly dependent on
the generator prompt, and varies widely among videos. We evaluate our summaries
extensively on multiple datasets; our results show that ViSMaP achieves
performance comparable to fully supervised state-of-the-art models while
generalising across domains without sacrificing performance. Code will be
released upon publication.