Speech Synthesis: English-US Multispeaker - HifiGAN Model Overview

Description:

The English-US Multispeaker FastPitch-HifiGAN model transcribes text into audio representations using two model components: FastPitch and HifiGAN. This model is ready for commercial use.

HifiGAN is a neural vocoder model for text-to-speech applications. It is the second part of a two-stage speech synthesis pipeline.

This HifiGAN model was trained to be used with a corresponding FastPitch model available here. FastPitch is a mel-spectrogram generator used as the first part of a neural text-to-speech system with a neural vocoder. This model uses the International Phonetic Alphabet (IPA) for inference and training, and it can output a female or a male voice for US English.

References:

FastPitch paper: https://arxiv.org/abs/2006.06873

HifiGAN paper: https://arxiv.org/abs/2010.05646

Model Architecture:

Architecture Type: Transformer + Generative Adversarial Network (GAN)

Network Architecture: FastPitch + HifiGAN

FastPitch is a fully-parallel text-to-speech transformer-based model, conditioned on fundamental frequency contours. The model predicts pitch contours during inference. By altering these predictions, the generated speech can be more expressive, better match the semantic of the utterance, and be engaging to the listener. FastPitch is based on a fully-parallel Transformer architecture, with much higher real-time factor than Tacotron2 for mel-spectrogram synthesis of a typical utterance.

HifiGAN is a neural vocoder based on a generative adversarial network framework. During training, the model uses a powerful discriminator consisting of small sub-discriminators, each one focusing on specific periodic parts of a raw waveform.

Input:

For FastPitch (1st Stage): Text Strings in English

Other Properties Related to Input: 400 Character Text String Limit

Output:

For HifiGAN (2nd Stage): Audio of shape (batch x time) in wav format

Other Parameters Related to Output: Mono, Encoded 16 bit audio; 20 Second Maximum Length; Depending on input, this model can output a female or a male voice for American English with six (6) emotions for the female voice and four (4) emotions for male voices. The female voice is classified as “neutral, calm, happy, angry, fearful, and sad.” The male voice is classified as “neutral,” “calm,” “happy,” and “angry.”

Software Integration:

Runtime Engine(s): Riva 2.13.0 or greater

Supported Hardware Platform(s):

• NVIDIA Volta V100
  
• NVIDIA Turing T4
  
• NVIDIA A100 GPU
  
• NVIDIA A30 GPU
  
• NVIDIA A10 GPU
  
• NVIDIA H100 GPU
  
• NVIDIA L4 GPU
  
• NVIDIA L40 GPU
  
• NVIDIA Jetson Orin
  
• NVIDIA Jetson AGX Xavier
  
• NVIDIA Jetson NX Xavier
  

Supported Operating System(s):

• Linux
  
• Linux 4 Tegra
  

Model Version(s):

HifiGAN_44k_EnglishUS_Emotion_Energy_IPA

Training & Evaluation:

Training Dataset:

** Data Collection Method by dataset

• Human
  Properties (Quantity, Dataset Descriptions, Sensor(s)): This model is trained on a proprietary dataset of audio-text pairs sampled at 44100 Hz, which contains one Female and one Male voice speaking US English. While both genders are trained for all emotions, this dataset only releases those that passed the evaluation standard for expressiveness and quality. The dataset also contains a subset of sentences with different words emphasized.
  

Evaluation Dataset:

** Data Collection Method by dataset

• Human
  Properties (Quantity, Dataset Descriptions, Sensor(s)): This model is trained on a proprietary dataset sampled at 44100 Hz, which contains one Female and one Male voice speaking US English. While both genders are trained for all emotions, this dataset only releases those that passed the evaluation standard for expressiveness and quality. The dataset also contains a subset of sentences with different words emphasized.
  

Inference:

Engine: Triton
Test Hardware:

• NVIDIA Volta V100
• NVIDIA Turing T4
• NVIDIA A100 GPU
• NVIDIA A30 GPU
• NVIDIA A10 GPU
• NVIDIA H100 GPU
• NVIDIA L4 GPU
• NVIDIA L40 GPU
• NVIDIA Jetson Orin
• NVIDIA Jetson AGX Xavier
• NVIDIA Jetson NX Xavier

Ethical Considerations:

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License

By downloading and using the models and resources packaged with Riva Conversational AI, you accept the terms of the Riva license.