LecTrans: A Multimodal Translation Benchmark for Academic Lectures

Frederikus Hudi, Nina Nanakorn, Justin Vasselli, Yusuke Sakai, Hidetaka Kamigaito, Akihiro Tamura, Taro Watanabe


Abstract
Existing machine translation and multimodal translation benchmarks mainly focus on text-only inputs or short examples with tightly aligned image-text pairs. Academic lectures present a different challenge: spoken explanations, presentation slides, and domain-specific terminology interact across long-form discourse. LecTrans is constructed from 383 hours of expert-taught online lectures and provides transcripts, presentation slides, and an eight-language parallel evaluation subset covering English and seven target languages. The 162-minute translation subset spans 17 subjects and contains human-corrected English transcripts, verified slide text, and human-verified translations of both transcripts and slides. We define lecture translation as two complementary tasks: transcript translation for spoken lecture content and slide translation for visually presented text. We report text-only and multimodal baselines, showing that noisy transcripts, loosely aligned slide context, and domain-specific content remain challenging for current systems. LecTrans provides a testbed for evaluating multimodal translation in long-form academic lectures.
Anthology ID:
2026.findings-aacl.93
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1872–1897
Language:
URL:
https://aclanthology.org/2026.findings-aacl.93/
DOI:
Bibkey:
Cite (ACL):
Frederikus Hudi, Nina Nanakorn, Justin Vasselli, Yusuke Sakai, Hidetaka Kamigaito, Akihiro Tamura, and Taro Watanabe. 2026. LecTrans: A Multimodal Translation Benchmark for Academic Lectures. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 1872–1897, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
LecTrans: A Multimodal Translation Benchmark for Academic Lectures (Hudi et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-aacl.93.pdf