appautomaton/fireredtts3-mlx

FireRedTTS3 for MLX

Multilingual voice cloning on Apple Silicon

Base BF16 · Pure MLX inference · Mono 24 kHz audio

Runtime guide · Source code · Upstream model · Project website

This repository brings FireRedTTS3 Base to mlx-speech as a complete MLX voice-cloning pipeline. Give it a reference recording, its transcript, and the text you want spoken. It returns a waveform in the reference speaker's voice.

App Automaton maintains the MLX conversion and runtime. Speech generation runs locally on your Mac, including speaker conditioning and waveform reconstruction.

The current release is Base BF16, stored in base/mlx-bf16/. Each model variant has its own complete inference bundle. Instruct will be added under instruct/ after its MLX pipeline is validated, keeping the Base path stable.

Start with a reference voice

Requires an Apple Silicon Mac and Python 3.13 or later.

pip install "mlx-speech>=0.5.3"

The loader downloads the Base bundle on first use. Replace reference.wav and reference_text with your recording and its exact transcript. A reference in the target language is preferred when available.

from mlx_speech import tts
from mlx_speech.audio import write_wav

model = tts.load(
    "appautomaton/fireredtts3-mlx",
    artifact_subdir="base/mlx-bf16",
)
result = model.generate(
    "你好，很高兴认识你。",
    reference_audio="reference.wav",
    reference_text="For Timothy was a spoiled cat, and he allowed no one.",
    language="Chinese",
    seed=1234,
    flow_steps=10,
    guidance_scale=2.0,
)
write_wav("generated.wav", result.waveform, sample_rate=result.sample_rate)

The aliases fireredtts3-base and fireredtts3-base-bf16 select the same bundle. Only base/mlx-bf16/ and the root model card are downloaded. Additional variants in this repository do not increase the size of a Base download.

The same request from the command line

mlx-speech tts \
  --model appautomaton/fireredtts3-mlx \
  --artifact-subdir base/mlx-bf16 \
  --text "你好，很高兴认识你。" \
  --reference-audio reference.wav \
  --reference-text "For Timothy was a spoiled cat, and he allowed no one." \
  --language Chinese \
  --seed 1234 \
  --flow-steps 10 \
  --guidance-scale 2.0 \
  --output generated.wav

One bundle, complete speech output

The model directory contains all three components and the tokenizer. No separate codec or speaker-model download is needed.

Component	Weight file	Size
Qwen3 and DiT speech-generation core	core.safetensors	3.950 GiB
RedAE waveform encoder and decoder	redae.safetensors	1.758 GiB
CAM++ speaker encoder	speaker.safetensors	0.014 GiB

config.json, tokenizer.json, tokenizer_config.json, and vocab.json sit beside the weight files at the directory root. The three weight files total 5.722 GiB. Inference also needs memory for activations and the KV cache.

Repository layout

README.md
LICENSE
base/
  mlx-bf16/
    config.json
    core.safetensors
    redae.safetensors
    speaker.safetensors
    tokenizer.json
    tokenizer_config.json
    vocab.json

A downloaded base/mlx-bf16/ directory also loads directly by local path. Base is the only model variant included in this release.

The conversion casts the original FP32 trainable weights to BF16 and maps their names and layouts for MLX. RedAE's ISTFT window and CAM++ running statistics remain FP32. This artifact uses 16-bit floating-point weights and does not apply INT8 or INT4 quantization.

Languages

The tokenizer accepts the upstream model's 24 language identifiers and 21 Chinese dialect tags. Pass an explicit language such as "English", "Chinese", or "Japanese" with each request.

Accepted language identifiers

Arabic, Cantonese, Chinese, Czech, Dutch, English, Finnish, French, German, Greek, Hindi, Indonesian, Italian, Japanese, Korean, Polish, Portuguese, Romanian, Russian, Spanish, Thai, Turkish, Ukrainian, and Vietnamese.

The dialect identifiers use the upstream ZH_ prefix, for example "ZH_Sichuan" and "ZH_Shanghai". The complete list is defined in the MLX tokenizer.

Language coverage comes from the upstream model and tokenizer. The local quality check below covers one Mandarin request with an English reference.

Local check

On the fixed request documented in the runtime guide:

Check	Result
Output	Finite, non-silent, mono 24 kHz waveform
Seed repeatability	Two bitwise-identical waveforms on one loaded model
Local ASR transcript	你好，很高兴认识你。
CAM++ reference/output cosine	0.7374

This covers one fixture only; it does not establish voice quality across other languages and recordings.

Current limits

• Base voice cloning requires both reference audio and its transcript. Instruct voice design and audio editing are outside this bundle.
• Generation handles one prepared utterance at a time, with batch size one and no waveform streaming.
• Supply the intended spoken form of numbers and abbreviations. Text normalization and automatic language detection are caller responsibilities.
• Long-form splitting and joining belong to the application. A local long-form test produced severe noise late in both the MLX output and the upstream reference, so long-passage quality remains a limitation.

Provenance and regression coverage

The conversion uses FireRedTeam's weights at dcf1bdcd and follows the official implementation at 1d32ba78. Both revisions are recorded in config.json.

The repository also retains small, deterministic golden fixtures for RedAE, CAM++, DiT, and autoregressive generation. They let maintainers check numerical regressions without keeping or downloading the full checkpoint. The fixture manifest records the BF16 bundle's SHA-256 hashes and capture provenance. Capture and replay use an explicit MLX CPU stream to keep these checks consistent between developer Macs and CI.

These fixtures exercise tiny models with reproducible synthetic weights. Checkpoint compatibility and full-model voice quality are covered by separate tests that require the real weights. The fixture guide documents the capture script and regression command.

License and attribution

FireRedTTS3 is developed by the FireRed Team and released under Apache 2.0. The MLX runtime and conversion code are maintained by App Automaton under the MIT license.

The upstream project describes voice cloning as intended for academic research. Use reference recordings with the speaker's permission and identify synthetic speech clearly. See the upstream model card for its intended-use statement.