Fish Speech is a production-grade multilingual text-to-speech system with a dual-autoregressive transformer architecture (4B parameter slow AR for temporal semantics, 400M fast AR for residual codebooks). It supports real-time voice cloning from short reference audio (10-30s), multi-speaker multi-turn generation, and fine-grained prosody/emotion control via natural language tags. The system is deployed through multiple interfaces: a Gradio web UI, a React-based modern web UI, a production ASGI API server (Kui) with streaming support, and command-line tools for inference and batch processing. Its architecture is modular: a TTSInferenceEngine orchestrates reference loading, LLM inference, and VQ decoding; an RVQ audio codec (10 codebooks, ~21 Hz frame rate) compresses audio; and the dual-AR model is structurally isomorphic to standard LLMs, enabling reuse of inference optimizations like paged KV cache and RadixAttention. The repository also includes training infrastructure (Lightning + Hydra) with LoRA fine-tuning, protobuf-based dataset pipelines, and a comprehensive i18n framework. While primarily a deployable application, it retains strong research character with published papers, benchmark results, and custom model implementations.

Bert-VITS2 is a multilingual text-to-speech system based on VITS2 (Variational Inference Text-to-Speech with improved Transformer backbone). It supports Chinese, Japanese, and English synthesis with optional emotion conditioning via pre-trained models (WavLM, wav2vec2-emotion, CLAP). The codebase provides a complete pipeline: data preprocessing (resampling, text normalization, BERT feature extraction), multi-speaker training with distributed support, inference through a Gradio web UI or FastAPI server (hiyoriUI.py), and ONNX export for deployment. The architecture uses separate per-language BERT models for text encoding, a flow-based decoder, stochastic duration predictor, and multi-scale discriminators (including a WavLM-based discriminator). The repository includes numerous versioned subdirectories (oldVersion/, onnx_modules/) for backward compatibility with model versions 1.0.1 through 2.4, resulting in significant code duplication and maintenance overhead. The README explicitly states the project is no longer maintained and recommends the successor project Fish-Speech.