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arxiv: 2604.10413 · v1 · submitted 2026-04-12 · 💻 cs.SD

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Sign-to-Speech Prosody Transfer via Sign Reconstruction-based GAN

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Pith reviewed 2026-05-10 16:33 UTC · model grok-4.3

classification 💻 cs.SD
keywords sign languageprosody transfergenerative adversarial networkspeech synthesiscross-modal learningemotional expressionunpaired training
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The pith

Sign language prosody transfers directly to synthesized speech via a reconstruction GAN trained on unpaired datasets.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper introduces the task of Sign-to-Speech Prosody Transfer to capture emotional and rhythmic nuances from signing and embed them in spoken output, bypassing the information loss that occurs when sign is first converted to text. It presents SignRecGAN, a framework that learns to align prosody representations by applying adversarial losses and sign reconstruction objectives to separate, unimodal sign-language and speech corpora, eliminating the need for expensive cross-modal annotations. The S2PFormer architecture then injects these learned prosody features into standard text-to-speech pipelines while retaining their expressive capacity. Experiments indicate that the generated speech better conveys the emotional content originally present in the signs. This approach matters because it enables scalable, more natural spoken communication from sign language without requiring expert-aligned parallel data.

Core claim

SignRecGAN trains on unimodal sign videos and speech recordings alone by reconstructing sign sequences from speech-derived latent features while using adversarial objectives to enforce distributional alignment of prosody; the resulting prosody embedding is then fed through S2PFormer into a TTS decoder, producing speech whose intonation and rhythm reflect the signer’s emotional state without any paired sign-speech examples or manual alignments.

What carries the argument

SignRecGAN, a generative adversarial network that combines sign reconstruction losses with cross-modal adversarial training to extract and align prosody representations from unpaired sign and speech data.

If this is right

  • Synthesized speech can carry the emotional prosody expressed in signing gestures rather than losing it at a text bottleneck.
  • Training remains scalable because no parallel sign-speech corpora or cross-modal annotations are required.
  • Existing TTS models can be extended with sign-derived prosody injection through the proposed S2PFormer module.
  • More natural spoken communication between signers and non-signers becomes feasible at large scale.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same reconstruction-plus-adversarial pattern could be tested for prosody transfer between other unpaired modalities such as gesture and text or facial expression and audio.
  • Live sign-interpretation systems might incorporate the method if inference latency is reduced, enabling real-time prosody-preserving speech output.
  • Generalization across different sign languages or dialects would require separate validation since the current experiments use specific datasets.
  • End-to-end pipelines could combine this prosody transfer with existing sign recognition modules to avoid any intermediate text stage.

Load-bearing premise

That prosodic features can be aligned across sign and speech modalities using only reconstruction objectives and adversarial distribution matching on separate unimodal datasets, without explicit paired examples or expert supervision.

What would settle it

A listening test in which raters judge emotional congruence between sign videos and the generated audio versus standard text-to-speech versions of the same content; absence of a statistically significant preference for the proposed output would falsify the central claim.

Figures

Figures reproduced from arXiv: 2604.10413 by Shinnosuke Takamichi, Toranosuke Manabe, Yoshimitsu Aoki, Yuto Shibata.

Figure 1
Figure 1. Figure 1: In the reference sign language video (left), the first phrase, “many Italians,” is emphasized through rapid hand movements and facial expressions. The two-stage baseline (middle) fails to reflect this prosody, whereas our approach (right) successfully captures the emphasis on “many.” Abstract. Deep learning models have improved sign language-to-text translation and made it easier for non-signers to underst… view at source ↗
Figure 2
Figure 2. Figure 2: The proposed learning framework of SignRecGAN. As shown in [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: The architecture of S2PFormer. S2PFormer extends FastSpeech2 by incorporat￾ing sign language information through a module called AdaPM. Specifically, the visual backbone converts sign language inputs into feature representations, which are then fed into AdaPM. Conditioned on these representations, the variance predictor estimates speech prosody parameters, which the prosody estimator uses to predict the or… view at source ↗
Figure 4
Figure 4. Figure 4: Adaptive Prosody Mixer velocity acceleration frequency hand face Sign Language Video time [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: An example of sign language prosody labels. The histograms represent the distribution of hand and face motion information in sign language videos. where wsign is the mean of weight for sign language features, and λweight is a hyperparameter that controls the strength of this regularization. 3.2 SignRec Loss To ensure that the speech synthesized by S2PFormer (Sec. 3.1) reflects sign language prosody, we int… view at source ↗
Figure 6
Figure 6. Figure 6: An example of input sign language video (left) and synthesized speech (right). 4.3 Ablation Study To investigate the effectiveness of each component in SignRecGAN, we conducted an ablation study. GAN, SignRec, and ProMo indicate the S2PFormer with the losses defined in Eqs. 10, 4, 5 respectively. The result in [PITH_FULL_IMAGE:figures/full_fig_p012_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Prominence analysis results. A black line on a spectrogram indicates emphasis, and the corresponding word is labeled on the spectrogram. The size of a labeled word indicates the intensity of the emphasis. 4.6 Emergence of Emphasis on Natural Words Regarding to fine-grained prosody evaluation, [PITH_FULL_IMAGE:figures/full_fig_p013_7.png] view at source ↗
read the original abstract

Deep learning models have improved sign language-to-text translation and made it easier for non-signers to understand signed messages. When the goal is spoken communication, a naive approach is to convert signed messages into text and then synthesize speech via Text-to-Speech (TTS). However, this two-stage pipeline inevitably treat text as a bottleneck representation, causing the loss of rich non-verbal information originally conveyed in the signing. To address this limitation, we propose a novel task, \emph{Sign-to-Speech Prosody Transfer}, which aims to capture the global prosodic nuances expressed in sign language and directly integrate them into synthesized speech. A major challenge is that aligning sign and speech requires expert knowledge, making annotation extremely costly and preventing the construction of large parallel corpora. To overcome this, we introduce \emph{SignRecGAN}, a scalable training framework that leverages unimodal datasets without cross-modal annotations through adversarial learning and reconstruction losses. Furthermore, we propose \emph{S2PFormer}, a new model architecture that preserves the expressive power of existing TTS models while enabling the injection of sign-derived prosody into the synthesized speech. Extensive experiments demonstrate that the proposed method can synthesize speech that faithfully reflects the emotional content of sign language, thereby opening new possibilities for more natural sign language communication. Our code will be available upon acceptance.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper introduces the task of Sign-to-Speech Prosody Transfer to capture prosodic and emotional nuances from sign language and inject them directly into TTS output, avoiding information loss from text intermediaries. It proposes SignRecGAN, trained on separate unimodal sign and speech corpora via adversarial distribution matching plus reconstruction losses, and S2PFormer to enable prosody injection while preserving existing TTS capabilities. The central claim is that this yields synthesized speech that faithfully reflects the emotional content of the input signs, supported by extensive experiments.

Significance. If validated, the work could meaningfully advance accessible communication tools by preserving non-verbal expressivity in sign-to-speech pipelines. The use of unimodal data for scalable training without costly cross-modal annotations is a practical strength. The stated intent to release code upon acceptance supports reproducibility and community follow-up.

major comments (2)
  1. [SignRecGAN framework] The SignRecGAN framework (method description) trains solely with adversarial and within-modality reconstruction objectives on unimodal datasets. This produces marginal distribution alignment but supplies no explicit mechanism or objective to guarantee that a sign-derived prosody code will modulate the correct pitch/energy/duration trajectory for the specific emotional nuance in the speech decoder; the S2PFormer injection therefore rests on an unverified semantic correspondence assumption.
  2. [Abstract / Experiments] The abstract asserts that 'extensive experiments demonstrate' faithful emotional reflection, yet the manuscript supplies no quantitative results, baselines, error bars, dataset sizes, or architectural diagrams. Without these, it is impossible to assess whether the data actually support the central claim of faithful prosody transfer.
minor comments (2)
  1. [Abstract] The abstract would be strengthened by briefly naming the evaluation metrics used for prosody similarity and emotional fidelity.
  2. [S2PFormer architecture] Clarify the precise interface between the sign encoder output and the S2PFormer injection point to aid reproducibility.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their insightful comments and the opportunity to clarify our work. We address the major comments point by point below and outline the revisions we plan to make.

read point-by-point responses
  1. Referee: [SignRecGAN framework] The SignRecGAN framework (method description) trains solely with adversarial and within-modality reconstruction objectives on unimodal datasets. This produces marginal distribution alignment but supplies no explicit mechanism or objective to guarantee that a sign-derived prosody code will modulate the correct pitch/energy/duration trajectory for the specific emotional nuance in the speech decoder; the S2PFormer injection therefore rests on an unverified semantic correspondence assumption.

    Authors: We agree that the training relies on distribution alignment via adversarial objectives and reconstruction losses rather than explicit paired supervision. The core assumption is that emotional nuances are expressed similarly across modalities, allowing the learned prosody codes to transfer meaningfully. The S2PFormer architecture is specifically designed to condition the TTS decoder on these codes at appropriate layers to influence prosodic features like pitch, energy, and duration. To strengthen this, we will add a detailed explanation of the model design rationale and include ablation studies or visualizations showing how the prosody codes affect the output trajectories in the revised manuscript. revision: partial

  2. Referee: [Abstract / Experiments] The abstract asserts that 'extensive experiments demonstrate' faithful emotional reflection, yet the manuscript supplies no quantitative results, baselines, error bars, dataset sizes, or architectural diagrams. Without these, it is impossible to assess whether the data actually support the central claim of faithful prosody transfer.

    Authors: We thank the referee for pointing this out. The current manuscript focuses on the method description in the main text, but we agree that quantitative results, baselines, error bars, dataset sizes, and architectural diagrams are essential to support the claims. We will add a comprehensive Experiments section with these elements, including objective and subjective evaluations, to the revised version. revision: yes

Circularity Check

0 steps flagged

No circularity in derivation chain

full rationale

The paper introduces SignRecGAN trained via adversarial distribution matching and within-modality reconstruction losses on separate unimodal sign and speech corpora, plus the S2PFormer architecture for prosody injection. No equations, derivations, or self-citations are shown that reduce the prosody-transfer claim to a fitted parameter defined by the target output itself or to a self-referential loop. The claimed alignment of sign-derived prosody with speech trajectories is presented as an empirical result of the training objectives and architecture rather than a definitional equivalence or renamed input. The derivation remains self-contained against external benchmarks and does not invoke load-bearing self-citations or uniqueness theorems from prior author work.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review supplies no explicit free parameters, axioms, or invented entities; the method appears to rest on standard GAN training assumptions and the premise that prosody can be extracted and injected via reconstruction losses.

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Reference graph

Works this paper leans on

34 extracted references · 16 canonical work pages · 2 internal anchors

  1. [1]

    Language91, e144 – e168 (2015).https://doi.org/10.1353/LAN.2015

    Brentari, D., Falk, J., Wolford, G.: The acquisition of prosody in american sign language. Language91, e144 – e168 (2015).https://doi.org/10.1353/LAN.2015. 0042

  2. [2]

    In: CVPR (June 2020)

    Camgoz, N.C., Koller, O., Hadfield, S., Bowden, R.: Sign language transformers: Joint end-to-end sign language recognition and translation. In: CVPR (June 2020)

  3. [3]

    In: Proceedings of the IEEE/CVF International Conference on Computer Vision (ICCV)

    Chen, Y., Zhang, Z., Yuan, C., Li, B., Deng, Y., Hu, W.: Channel-wise topology refinement graph convolution for skeleton-based action recognition. In: Proceedings of the IEEE/CVF International Conference on Computer Vision (ICCV). pp. 13359– 13368 (October 2021)

  4. [4]

    Contributors, M.: Openmmlab pose estimation toolbox and benchmark (2020), https://github.com/open-mmlab/mmpose

  5. [5]

    International Journal for Research in Applied Science and Engineering Technology (2023).https://doi

    Dangat, P.M.T.: Sign language to speech conversion. International Journal for Research in Applied Science and Engineering Technology (2023).https://doi. org/10.22214/ijraset.2023.56174

  6. [6]

    In: CVPR

    Duarte, A., Palaskar, S., Ventura, L., Ghadiyaram, D., DeHaan, K., Metze, F., Tor- res, J., Giro-i Nieto, X.: How2sign: A large-scale multimodal dataset for continuous american sign language. In: CVPR. pp. 2735–2744 (June 2021)

  7. [7]

    In: CVPR

    Gong, J., Foo, L.G., He, Y., Rahmani, H., Liu, J.: Llms are good sign language translators. In: CVPR. pp. 18362–18372 (June 2024)

  8. [8]

    V oxCeleb: A Large-Scale Speaker Identification Dataset

    Karlapati, S., Moinet, A., Joly, A., Klimkov, V., Sáez-Trigueros, D., Drugman, T.: Copycat: Many-to-many fine-grained prosody transfer for neural text-to-speech. In: Interspeech 2020. pp. 4387–4391 (2020).https://doi.org/10.21437/Interspeech. 2020-1251

  9. [10]

    In: Interspeech 2019

    Klimkov, V., Ronanki, S., Rohnke, J., Drugman, T.: Fine-grained robust prosody transfer for single-speaker neural text-to-speech. In: Interspeech 2019. pp. 4440–4444 (2019).https://doi.org/10.21437/Interspeech.2019-2571

  10. [11]

    Language, Interaction and Acquisition (01 2010)

    Limousin, F., Blondel, M.: Prosodie et acquisition de la langue des signes française. Language, Interaction and Acquisition (01 2010)

  11. [12]

    In: Proceedings of the 61st Annual Meeting of the Asso- ciation for Computational Linguistics (Volume 1: Long Papers)

    Lin, K., Wang, X., Zhu, L., Sun, K., Zhang, B., Yang, Y.: Gloss-free end-to-end sign language translation. In: Proceedings of the 61st Annual Meeting of the Asso- ciation for Computational Linguistics (Volume 1: Long Papers). pp. 12904–12916. Association for Computational Linguistics, Toronto, Canada (Jul 2023).https: //doi.org/10.18653/v1/2023.acl-long.7...

  12. [13]

    In: CVPR (June 2020)

    Liu, Z., Zhang, H., Chen, Z., Wang, Z., Ouyang, W.: Disentangling and unifying graph convolutions for skeleton-based action recognition. In: CVPR (June 2020)

  13. [14]

    In: International Conference on Learning Representations (2019),https://openreview.net/forum? id=Bkg6RiCqY7

    Loshchilov, I., Hutter, F.: Decoupled weight decay regularization. In: International Conference on Learning Representations (2019),https://openreview.net/forum? id=Bkg6RiCqY7

  14. [15]

    In: Proceedings of the IEEE International Conference on Computer Vision (ICCV) (Oct 2017) Sign-to-Speech Prosody Transfer via Sign Reconstruction-based GAN 15

    Mao, X., Li, Q., Xie, H., Lau, R.Y., Wang, Z., Paul Smolley, S.: Least squares gen- erative adversarial networks. In: Proceedings of the IEEE International Conference on Computer Vision (ICCV) (Oct 2017) Sign-to-Speech Prosody Transfer via Sign Reconstruction-based GAN 15

  15. [16]

    McAuliffe, M., Socolof, M., Mihuc, S., Wagner, M., Sonderegger, M.: Montreal forced aligner: Trainable text-speech alignment using kaldi. pp. 498–502 (08 2017). https://doi.org/10.21437/Interspeech.2017-1386

  16. [17]

    International journal of engineering research and technology8(2020)

    Ojha, A., Pandey, A., Maurya, S., Thakur, A., Dayananda, P.: Sign language to text and speech translation in real time using convolutional neural network. International journal of engineering research and technology8(2020)

  17. [18]

    2022 IEEE 2nd Mysore Sub Section International Conference (MysuruCon) pp

    R, S., Hegde, S.R., K, C., Priyesh, A., Manjunath, A.S., Arunakumari, B.: Indian sign language to speech conversion using convolutional neural network. 2022 IEEE 2nd Mysore Sub Section International Conference (MysuruCon) pp. 1–5 (2022). https://doi.org/10.1109/MysuruCon55714.2022.9972574

  18. [19]

    Robust Speech Recognition via Large-Scale Weak Supervision

    Radford, A., Kim, J.W., Xu, T., Brockman, G., McLeavey, C., Sutskever, I.: Robust speech recognition via large-scale weak supervision (2022).https://doi.org/10. 48550/ARXIV.2212.04356,https://arxiv.org/abs/2212.04356

  19. [20]

    In: International Conference on Learning Representations (2021),https://openreview.net/forum?id=piLPYqxtWuA

    Ren, Y., Hu, C., Tan, X., Qin, T., Zhao, S., Zhao, Z., Liu, T.Y.: Fastspeech 2: Fast and high-quality end-to-end text to speech. In: International Conference on Learning Representations (2021),https://openreview.net/forum?id=piLPYqxtWuA

  20. [21]

    In: CVPR

    Rombach, R., Blattmann, A., Lorenz, D., Esser, P., Ommer, B.: High-resolution image synthesis with latent diffusion models. In: CVPR. pp. 10684–10695 (June 2022)

  21. [22]

    In: Interspeech 2022

    Saeki, T., Xin, D., Nakata, W., Koriyama, T., Takamichi, S., Saruwatari, H.: Utmos: Utokyo-sarulab system for voicemos challenge 2022. In: Interspeech 2022. pp. 4521–4525 (2022).https://doi.org/10.21437/Interspeech.2022-439

  22. [23]

    2020 11th International Conference on Computing, Communication and Networking Technologies (ICCCNT) pp

    Sharma, A., Panda, S., Verma, S.: Sign language to speech translation. 2020 11th International Conference on Computing, Communication and Networking Technologies (ICCCNT) pp. 1–8 (2020).https://doi.org/10.1109/ICCCNT49239. 2020.9225422

  23. [24]

    Shazeer, N., Mirhoseini, A., Maziarz, K., Davis, A., Le, Q., Hinton, G., Dean, J.: Outrageously large neural networks: The sparsely-gated mixture-of-experts layer (2017),https://arxiv.org/abs/1701.06538

  24. [25]

    InProceedings of the 2025 Conference on Empirical Methods in Natural Language Processing

    Shi, B., Brentari, D., Shakhnarovich, G., Livescu, K.: Open-domain sign language translation learned from online video. In: Goldberg, Y., Kozareva, Z., Zhang, Y. (eds.) Proceedings of the 2022 Conference on Empirical Methods in Natural Language Processing. pp. 6365–6379. Association for Computational Linguistics, Abu Dhabi, United Arab Emirates (Dec 2022)...

  25. [26]

    In: Dy, J., Krause, A

    Skerry-Ryan, R., Battenberg, E., Xiao, Y., Wang, Y., Stanton, D., Shor, J., Weiss, R., Clark, R., Saurous, R.A.: Towards end-to-end prosody transfer for expressive speech synthesis with tacotron. In: Dy, J., Krause, A. (eds.) Proceedings of the 35th International Conference on Machine Learning. Proceedings of Machine Learning Research, vol. 80, pp. 4693–4...

  26. [27]

    CoRRabs/1510.01949(2015), http://arxiv.org/abs/1510

    Suni, A., Aalto, D., Vainio, M.: Hierarchical representation of prosody for statistical speech synthesis. CoRRabs/1510.01949(2015), http://arxiv.org/abs/1510. 01949

  27. [28]

    In: Interspeech

    Swiatkowski, J., Wang, D., Babianski, M., Lumban Tobing, P., Vipperla, R., Pollet, V.: Cross-lingual prosody transfer for expressive machine dubbing. In: Interspeech

  28. [29]

    4838–4842 (2023).https://doi.org/10.21437/Interspeech.2023-437

    pp. 4838–4842 (2023).https://doi.org/10.21437/Interspeech.2023-437

  29. [30]

    In: Guyon, I., Luxburg, U.V., Bengio, S., Wallach, H., Fergus, R., Vishwanathan, S., Garnett, R

    Vaswani, A., Shazeer, N., Parmar, N., Uszkoreit, J., Jones, L., Gomez, A.N., Kaiser, L.u., Polosukhin, I.: Attention is all you need. In: Guyon, I., Luxburg, U.V., Bengio, S., Wallach, H., Fergus, R., Vishwanathan, S., Garnett, R. (eds.) 16 T. Manabe et al. Advances in Neural Information Processing Systems. vol. 30. Curran Associates, Inc. (2017), https:/...

  30. [31]

    Language and speech42 ( Pt 2-3), 229–50 (04 1999)

    Wilbur, R.: Stress in- asl: Empirical evidence and linguistic issues. Language and speech42 ( Pt 2-3), 229–50 (04 1999)

  31. [32]

    Yamagishi, J., Veaux, C., MacDonald, K.: Cstr vctk corpus: English multi-speaker corpus for cstr voice cloning toolkit (2017).https://doi.org/10.7488/ds/1994

  32. [33]

    In: The Eleventh International Conference on Learning Rep- resentations (2023),https://openreview.net/forum?id=EBS4C77p_5S

    Zhang, B., Müller, M., Sennrich, R.: SLTUNET: A simple unified model for sign language translation. In: The Eleventh International Conference on Learning Rep- resentations (2023),https://openreview.net/forum?id=EBS4C77p_5S

  33. [34]

    In: Globerson, A., Mackey, L., Belgrave, D., Fan, A., Paquet, U., Tomczak, J., Zhang, C

    Zhang, B., Tanzer, G., Firat, O.: Scaling sign language translation. In: Globerson, A., Mackey, L., Belgrave, D., Fan, A., Paquet, U., Tomczak, J., Zhang, C. (eds.) Advances in Neural Information Processing Systems. vol. 37, pp. 114018–114047. Curran Associates, Inc. (2024),https://proceedings.neurips.cc/paper_files/ paper/2024/file/ced76a666704e381c30398...

  34. [35]

    Nature Electronics3, 571 – 578 (2020).https://doi.org/10.1038/s41928-020-0428-6

    Zhou, Z., Chen, K., Li, X., Zhang, S., Wu, Y., Zhou, Y., Meng, K., Sun, C., He, Q., Fan, W., Fan, E., Lin, Z., Tan, X., Deng, W., Yang, J., Chen, J.: Sign-to- speech translation using machine-learning-assisted stretchable sensor arrays. Nature Electronics3, 571 – 578 (2020).https://doi.org/10.1038/s41928-020-0428-6