SignGraph: A Sign Sequence is Worth Graphs of Nodes

Despite the recent success of sign language research, the widely adopted CNN-based backbones are mainly migrated from other computer vision tasks, in which the contours and texture of objects are crucial for {identifying} objects. They usually treat sign frames as grids and may fail to capture effective cross-region features. In fact, sign language tasks need to focus on the correlation of different regions in one frame and the interaction of different regions among adjacent frames for {identifying} a sign sequence. In this paper, we propose to represent a sign sequence as graphs and introduce a simple yet effective graph-based sign language processing architecture named SignGraph, to extract cross-region features at the graph level. SignGraph consists of two basic modules: Local Sign Graph ($LSG$) module for learning the correlation of \textbf{intra-frame cross-region} features in one frame and Temporal Sign Graph ($TSG$) module for tracking the interaction of \textbf{inter-frame cross-region} features among adjacent frames. With $LSG$ and $TSG$, we build our model in a multiscale manner to ensure that the representation of nodes can capture cross-region features at different granularities. Extensive experiments on current public sign language datasets demonstrate the superiority of our SignGraph model. Our model achieves very competitive performances with the SOTA model, while not using any extra cues. Code and models are available at: \href{https://github.com/gswycf/SignGraph}{\textcolor{blue}{https://github.com/gswycf/SignGraph}}.