Contrastive Pretraining with Dual Visual Encoders for Gloss-Free Sign Language Translation

Abstract

Sign Language Translation (SLT) aims to convert sign language videos into spoken or written text. While early systems relied on gloss annotations as an intermediate supervision, such annotations are costly to obtain and often fail to capture the full complexity of continuous signing. In this work, we propose a two-phase, dual visual encoder framework for gloss-free SLT, leveraging contrastive visual-language pretraining. During pretraining, our approach employs two complementary visual backbones whose outputs are jointly aligned with each other and with sentence-level text embeddings via a contrastive objective. During the downstream SLT task, we fuse the visual features and input them into an encoder-decoder model. On the Phoenix-2014T benchmark, our dual encoder architecture consistently outperforms its single-stream variants and achieves the highest BLEU-4 score among existing gloss-free SLT approaches.