# Voxtral TTS

[mistralai/Voxtral-4B-TTS-2603](https://huggingface.co/mistralai/Voxtral-4B-TTS-2603)
— Mistral AI's 4B open-weight streaming TTS, served via the
[vLLM-Omni](https://github.com/vllm-project/vllm-omni) production
serving stack (Mistral co-developed). Released March 28, 2026.

## ⚠️ License

**CC BY-NC.** Personal use, research, and internal tooling are fine.
**Don't ship Voxtral output in any commercial product** without
re-licensing from Mistral. The other TTS in this fleet (Kokoro,
Chatterbox, Fish S2-Pro, IndexTTS-2, Qwen3-TTS, CosyVoice) are all
open-licensed and clean for commercial work.

## Why this stack exists

Multilingual streaming with serious speed:

| | use case |
|---|---|
| **Voxtral** | multilingual EN/FR/DE/ES/IT/PT/NL/HI streaming, 70 ms model latency |
| Kokoro | low-latency English, fixed voice library |
| Chatterbox Turbo | low-latency English w/ cloning + 9 paralinguistic tags |
| Fish Audio S2-Pro | richest paralinguistic English (15k+ tags) |
| IndexTTS-2 | English voice cloning + emotion vector / text control |
| Qwen3-TTS-1.7B | English voice cloning (slow on official backend) |
| CosyVoice 3 | multilingual (Chinese-leaning) |
| VibeVoice 1.5B | long-form / multi-speaker dialogue |

Voxtral fills the **multilingual + low-latency + cloning** slot
that's been weak in the fleet (CosyVoice is multilingual but slow on
English; nothing else is multilingual at all).

## Headline numbers

- **70 ms** model latency for a typical 10 s sample (500-char input)
- **9.7×** realtime factor
- **68.4%** blind A/B win rate vs ElevenLabs Flash v2.5 in voice
  cloning evaluations
- **8 languages**: EN, FR, DE, ES, IT, PT, NL, HI

## API

vLLM-Omni serves an OpenAI-compatible API at
`http://10.100.79.3:8201/v1`:

```bash
# Single-shot synthesis.
curl -fsS -X POST http://10.100.79.3:8201/v1/audio/speech \
  -H 'Content-Type: application/json' \
  -d '{"model":"mistralai/Voxtral-4B-TTS-2603","input":"Hello there.","voice":"alloy","response_format":"wav"}' \
  > out.wav

# Streaming.
curl -fsS -X POST http://10.100.79.3:8201/v1/audio/speech \
  -H 'Content-Type: application/json' \
  -d '{"model":"mistralai/Voxtral-4B-TTS-2603","input":"long passage…","voice":"alloy","stream":true}' \
  | mpv --no-cache -

# vLLM-Omni standard endpoints.
curl http://10.100.79.3:8201/v1/models    # confirms model loaded
curl http://10.100.79.3:8201/v1/audio/voices  # built-in + cloned voices
```

## Deploy

```bash
scripts/elway irv-ml1 --playbook playbooks/deploy-voxtral.yaml
```

First boot pulls Voxtral-4B (~8 GB BF16) into the HF cache + warms
vLLM. Both are cached afterwards.

## Hardware footprint

- **VRAM**: ~16 GB practical (8 GB weights + KV + activation). Pinned
  to GPU 1 (RTX A6000) by default — comfortable headroom. The 3090's
  24 GB CAN fit but it's tight for long streaming sessions.
- **Disk**: ~8 GB for the Voxtral checkpoint + HF cache.

## Voice library

Drop reference WAV / FLAC into `/worktank/voxtral/voices/` on the
host. The wrapper scans on request — no restart needed.
