CosyVoice — Multilingual Voice Generation with LLM-Based TTS

Introduction

CosyVoice is a large-scale text-to-speech model that uses an LLM backbone to generate natural, expressive speech. It handles multilingual synthesis, voice cloning from a short reference clip, and controllable speaking styles without per-speaker fine-tuning.

What CosyVoice Does

• Generates speech in 9 languages: Chinese, English, Japanese, Korean, German, Spanish, French, Italian, Russian
• Performs zero-shot voice cloning from a few seconds of reference audio
• Supports streaming TTS for real-time applications
• Provides instruction-following synthesis for emotion and style control
• Enables cross-lingual voice cloning (clone a voice and speak in a different language)

Architecture Overview

CosyVoice uses a two-stage pipeline. The first stage is an autoregressive LLM that converts text tokens and speaker embeddings into semantic speech tokens. The second stage is a flow-matching-based acoustic model that transforms semantic tokens into a mel spectrogram, which a HiFi-GAN vocoder renders into a waveform. Speaker identity is captured by a reference encoder that extracts a fixed-dimensional embedding from a short audio prompt.

Self-Hosting & Configuration

• Clone the repo and install dependencies (Python 3.10+, PyTorch 2.0+)
• Download pretrained model weights via the provided script or from ModelScope/Hugging Face
• Launch the Gradio web UI with webui.py for interactive testing
• Configure GPU memory, batch size, and streaming chunk size in the config YAML
• Deploy as an API server using the included FastAPI wrapper for production use

Key Features

• LLM-based architecture produces more natural prosody than traditional TTS pipelines
• Zero-shot cloning requires only 3-10 seconds of reference audio
• Streaming mode enables sub-200ms first-chunk latency for real-time applications
• Supports fine-tuning on custom data for domain adaptation
• Covers 18+ Chinese regional dialects and accents

Comparison with Similar Tools

• Bark — generates speech, music, and sound effects; CosyVoice focuses on high-fidelity multilingual speech
• F5-TTS — flow-matching TTS with zero-shot cloning; CosyVoice adds an LLM stage for better prosody
• Kokoro — lightweight 82M-parameter TTS; CosyVoice trades model size for richer multilingual and style control
• Fish Speech — multilingual TTS with VITS architecture; CosyVoice uses an LLM backbone for longer context
• GPT-SoVITS — few-shot voice cloning focused on Chinese; CosyVoice supports 9 languages natively

FAQ

Q: How much reference audio is needed for voice cloning? A: As little as 3 seconds, though 5-10 seconds of clean speech produces better results.

Q: Can CosyVoice run in real-time? A: Yes. Streaming mode delivers audio chunks with low latency, suitable for voice assistants and live applications.

Q: What hardware is required? A: A single GPU with 8 GB VRAM is sufficient for inference. Training and fine-tuning require more resources.

Q: Is commercial use allowed? A: CosyVoice is released under the Apache 2.0 license, permitting commercial use.

Sources

• https://github.com/FunAudioLLM/CosyVoice
• https://fun-audio-llm.github.io/cosyvoice/