Collaborative Viseme Subword and End-to-end Modeling for Word-level Lip Reading

We propose a viseme subword modeling (VSM) approach to improve the generalizability and interpretability capabilities of deep neural network based lip reading. A comprehensive analysis of preliminary experimental results reveals the complementary nature of the conventional end-to-end (E2E) and proposed VSM frameworks, especially concerning speaker head movements. To increase lip reading accuracy, we propose hybrid viseme subwords and end-to-end modeling (HVSEM), which exploits the strengths of both approaches through multitask learning. As an extension to HVSEM, we also propose collaborative viseme subword and end-to-end modeling (CVSEM), which further explores the synergy between the VSM and E2E frameworks by integrating a state-mapped temporal mask (SMTM) into joint modeling. Experimental evaluations using different model backbones on both the LRW and LRW-1000 datasets confirm the superior performance and generalizability of the proposed frameworks. Specifically, VSM outperforms the baseline E2E framework, while HVSEM outperforms VSM in a hybrid combination of VSM and E2E modeling. Building on HVSEM, CVSEM further achieves impressive accuracies on 90.75% and 58.89%, setting new benchmarks for both datasets.