This paper presents a novel transformer-based framework for unsupervised
activity segmentation which leverages not only frame-level cues but also
segment-level cues. This is in contrast with previous methods which often rely
on frame-level information only. Our approach begins with a frame-level
prediction module which estimates framewise action classes via a transformer
encoder. The frame-level prediction module is trained in an unsupervised manner
via temporal optimal transport. To exploit segment-level information, we
introduce a segment-level prediction module and a frame-to-segment alignment
module. The former includes a transformer decoder for estimating video
transcripts, while the latter matches frame-level features with segment-level
features, yielding permutation-aware segmentation results. Moreover, inspired
by temporal optimal transport, we develop simple-yet-effective pseudo labels
for unsupervised training of the above modules. Our experiments on four public
datasets, i.e., 50 Salads, YouTube Instructions, Breakfast, and Desktop
Assembly show that our approach achieves comparable or better performance than
previous methods in unsupervised activity segmentation.

本文提出了一种新颖的基于 Transformer 的框架，用于无监督活动分割，利用帧级别线索和段级别线索。我们的方法通过一个帧级别预测模块开始，该模块通过 Transformer 编码器估计逐帧动作类别。为了利用段级别信息，我们引入了一个段级别预测模块和一个帧到段对齐模块。