OmniFusion: Simultaneous Multilingual and Multimodal Translations via Modular Fusion

Sai Koneru, Matthias Huck, Jan Niehues


Abstract
Open-source text-only translation LLMs have rapidly improved multilingual coverage and translation quality, but their unimodal design limits their use in multimodal translation. In speech translation, they are commonly used in cascaded ASR–MT pipelines, which introduce additional latency and prevent the translation model from directly using visual context. Conversely, pretrained multimodal foundation models provide strong audio-visual perception but generally lag behind specialized translation LLMs in multilingual generation quality. We introduce OmniFusion, a modular architecture that connects a frozen multimodal foundation model to a translation-specialized LLM through a lightweight gated fusion module. OmniFusion supports speech-to-text, speech-and-image-to-text, and text-and-image-to-text translation within a single framework. Experiments with Qwen2.5-Omni-7B and Seed-X-PPO-7B show that selected early and middle MMFM layers provide more transferable representations than late layers. On MCIF, OmniFusion improves the latency–quality trade-off over a matched cascaded SimulST pipeline when evaluated with Local Agreement decoding, while remaining competitive in offline ST and reducing severe XCOMET-XL errors. On CoMMuTE, it achieves competitive visually grounded caption translation performance.
Anthology ID:
2026.findings-emnlp.320
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
6770–6788
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.320/
DOI:
Bibkey:
Cite (ACL):
Sai Koneru, Matthias Huck, and Jan Niehues. 2026. OmniFusion: Simultaneous Multilingual and Multimodal Translations via Modular Fusion. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 6770–6788, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
OmniFusion: Simultaneous Multilingual and Multimodal Translations via Modular Fusion (Koneru et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.320.pdf