@inproceedings{liu-etal-2026-emotra,
title = "{E}mo{T}ra-{TTS}: Smooth Intra-Utterance Emotion Transitions for Speech Synthesis",
author = "Liu, Tianchi and
Song, Zeyang and
Wang, Tianrui and
Li, Zhipeng and
Xu, Chenglin and
Guo, Steven Y.",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-main.736/",
pages = "17073--17091",
ISBN = "979-8-89176-459-0",
abstract = "Psychological research on emotion dynamics has established that human affect is a continuous, evolving process: emotions rise, decay, and transition within seconds. Current emotional text-to-speech (TTS) systems, however, condition on a single discrete label or static embedding per utterance, fundamentally misaligning with the temporal nature of affect. While recent LLM-based TTS systems may implicitly vary prosody through text understanding, such variation is neither explicitly controllable nor precise enough for targeted intra-utterance transitions. We address three challenges: (1) a multi-pass flow blending pipeline synthesizes frame-aligned transition audio, circumventing the scarcity of natural intra-utterance transitions; (2) dual-stage Valence{--}Arousal{--}Dominance (VAD) conditioning guides prosodic planning in the LLM and acoustic realization in the flow decoder via frame-level VAD embeddings; (3) direction{--}magnitude decoupled injection structurally separates emotion direction from injection magnitude, preventing content degradation. EmoTra-TTS adds only +0.43{\%} parameters with no latency overhead, achieves 30{\%}{--}87{\%} relative improvement on emotion transition quality, corroborated by 67.5{\%}{--}79.5{\%} overall win rates in a pairwise preference test against four SOTA baselines. The complete code, including data synthesis and training pipelines, will be released after the review process."
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<abstract>Psychological research on emotion dynamics has established that human affect is a continuous, evolving process: emotions rise, decay, and transition within seconds. Current emotional text-to-speech (TTS) systems, however, condition on a single discrete label or static embedding per utterance, fundamentally misaligning with the temporal nature of affect. While recent LLM-based TTS systems may implicitly vary prosody through text understanding, such variation is neither explicitly controllable nor precise enough for targeted intra-utterance transitions. We address three challenges: (1) a multi-pass flow blending pipeline synthesizes frame-aligned transition audio, circumventing the scarcity of natural intra-utterance transitions; (2) dual-stage Valence–Arousal–Dominance (VAD) conditioning guides prosodic planning in the LLM and acoustic realization in the flow decoder via frame-level VAD embeddings; (3) direction–magnitude decoupled injection structurally separates emotion direction from injection magnitude, preventing content degradation. EmoTra-TTS adds only +0.43% parameters with no latency overhead, achieves 30%–87% relative improvement on emotion transition quality, corroborated by 67.5%–79.5% overall win rates in a pairwise preference test against four SOTA baselines. The complete code, including data synthesis and training pipelines, will be released after the review process.</abstract>
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%0 Conference Proceedings
%T EmoTra-TTS: Smooth Intra-Utterance Emotion Transitions for Speech Synthesis
%A Liu, Tianchi
%A Song, Zeyang
%A Wang, Tianrui
%A Li, Zhipeng
%A Xu, Chenglin
%A Guo, Steven Y.
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-459-0
%F liu-etal-2026-emotra
%X Psychological research on emotion dynamics has established that human affect is a continuous, evolving process: emotions rise, decay, and transition within seconds. Current emotional text-to-speech (TTS) systems, however, condition on a single discrete label or static embedding per utterance, fundamentally misaligning with the temporal nature of affect. While recent LLM-based TTS systems may implicitly vary prosody through text understanding, such variation is neither explicitly controllable nor precise enough for targeted intra-utterance transitions. We address three challenges: (1) a multi-pass flow blending pipeline synthesizes frame-aligned transition audio, circumventing the scarcity of natural intra-utterance transitions; (2) dual-stage Valence–Arousal–Dominance (VAD) conditioning guides prosodic planning in the LLM and acoustic realization in the flow decoder via frame-level VAD embeddings; (3) direction–magnitude decoupled injection structurally separates emotion direction from injection magnitude, preventing content degradation. EmoTra-TTS adds only +0.43% parameters with no latency overhead, achieves 30%–87% relative improvement on emotion transition quality, corroborated by 67.5%–79.5% overall win rates in a pairwise preference test against four SOTA baselines. The complete code, including data synthesis and training pipelines, will be released after the review process.
%U https://aclanthology.org/2026.emnlp-main.736/
%P 17073-17091
Markdown (Informal)
[EmoTra-TTS: Smooth Intra-Utterance Emotion Transitions for Speech Synthesis](https://aclanthology.org/2026.emnlp-main.736/) (Liu et al., EMNLP 2026)
ACL