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arXiv · 2306.01442

Towards Robust FastSpeech 2 by Modelling Residual Multimodality

Fabian Kögel·Bac Nguyen·Fabien Cardinaux
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Abstract

State-of-the-art non-autoregressive text-to-speech (TTS) models based on FastSpeech 2 can efficiently synthesise high-fidelity and natural speech. For expressive speech datasets however, we observe characteristic audio distortions. We demonstrate that such artefacts are introduced to the vocoder reconstruction by over-smooth mel-spectrogram predictions, which are induced by the choice of mean-squared-error (MSE) loss for training the mel-spectrogram decoder. With MSE loss FastSpeech 2 is limited to learn conditional averages of the training distribution, which might not lie close to a natural sample if the distribution still appears multimodal after all conditioning signals. To alleviate this problem, we introduce TVC-GMM, a mixture model of Trivariate-Chain Gaussian distributions, to model the residual multimodality. TVC-GMM reduces spectrogram smoothness and improves perceptual audio quality in particular for expressive datasets as shown by both objective and subjective evaluation.

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Fabian Kögel, Bac Nguyen, Fabien Cardinaux. 2023-06-02. Towards Robust FastSpeech 2 by Modelling Residual Multimodality. https://doi.org/10.21437/interspeech.2023-879

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