FlexiSLM: A Spoken Language Model with Dynamic and Controllable Frame Rates

Jiaqi Li, Chaoren Wang, Xiaohai Tian, Mingjie Chen, Xinyu Liang, Xu Li, Yufan Lin, Junwen Qiu, Jun Zhang, Lu Lu, Zhizheng Wu


Abstract
Spoken language models (SLMs) extend LLMs to speech input and output, but existing systems use fixed frame rates (e.g., 25 or 12.5 Hz), overlooking speech’s time-varying information density and limiting inference-time quality–speed tradeoffs. Recent dynamic-frame-rate audio tokenizers enable very low average frame rates and controllability, yet had not been applied to SLMs. We introduce FlexiSLM, the first SLM with dynamic, controllable frame rates, using pretrained FlexiCodec for dynamic speech output tokens. It integrates this representation into a multi-task speech-to-speech SLM, extends it with input-side frame compression, and adds direct frame-rate conditioning for accurate control during inference. FlexiSLM outperforms fixed-frame-rate 7B models, including Qwen2.5-Omni and Kimi-Audio, at 12.5 and 6.25 Hz; it can be steered down to 4.0 Hz, and at 6.25 Hz roughly halves inference time relative to 12.5 Hz while retaining strong speech-to-speech quality. Audio samples: https://flexislm.github.io; code and data: https://github.com/AmphionTeam/FlexiSLM.
Anthology ID:
2026.emnlp-main.497
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
11417–11440
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URL:
https://aclanthology.org/2026.emnlp-main.497/
DOI:
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Cite (ACL):
Jiaqi Li, Chaoren Wang, Xiaohai Tian, Mingjie Chen, Xinyu Liang, Xu Li, Yufan Lin, Junwen Qiu, Jun Zhang, Lu Lu, and Zhizheng Wu. 2026. FlexiSLM: A Spoken Language Model with Dynamic and Controllable Frame Rates. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 11417–11440, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
FlexiSLM: A Spoken Language Model with Dynamic and Controllable Frame Rates (Li et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.497.pdf