SMC-NCA: Semantic-guided Multi-level Contrast for Semi-supervised Temporal Action Segmentation
This work addresses the challenge of limited labeled data for video action segmentation, which is important for applications like behavior analysis, but it appears incremental as it builds on existing contrastive learning approaches.
The paper tackles the problem of semi-supervised temporal action segmentation in videos by proposing SMC-NCA, a method that uses semantic-guided multi-level contrast and neighbourhood-consistency-aware units to improve frame-wise representation learning, achieving up to 17.8% and 12.6% improvements in Edit distance and accuracy on benchmarks.
Semi-supervised temporal action segmentation (SS-TA) aims to perform frame-wise classification in long untrimmed videos, where only a fraction of videos in the training set have labels. Recent studies have shown the potential of contrastive learning in unsupervised representation learning using unlabelled data. However, learning the representation of each frame by unsupervised contrastive learning for action segmentation remains an open and challenging problem. In this paper, we propose a novel Semantic-guided Multi-level Contrast scheme with a Neighbourhood-Consistency-Aware unit (SMC-NCA) to extract strong frame-wise representations for SS-TAS. Specifically, for representation learning, SMC is first used to explore intra- and inter-information variations in a unified and contrastive way, based on action-specific semantic information and temporal information highlighting relations between actions. Then, the NCA module, which is responsible for enforcing spatial consistency between neighbourhoods centered at different frames to alleviate over-segmentation issues, works alongside SMC for semi-supervised learning (SSL). Our SMC outperforms the other state-of-the-art methods on three benchmarks, offering improvements of up to 17.8% and 12.6% in terms of Edit distance and accuracy, respectively. Additionally, the NCA unit results in significantly better segmentation performance in the presence of only 5% labelled videos. We also demonstrate the generalizability and effectiveness of the proposed method on our Parkinson Disease's Mouse Behaviour (PDMB) dataset. Code is available at https://github.com/FeixiangZhou/SMC-NCA.