# Text-To-Speech (Online Serving)

vLLM-Omni exposes TTS models through the OpenAI-compatible
[`POST /v1/audio/speech`](../../../docs/serving/speech_api.md) endpoint,
launched with `vllm serve <model> --omni`. Each TTS model has its own
subdirectory containing client snippets, gradio demos, and helper
scripts; this README is the single doc entry point for all of them.

For offline inference, see [`examples/offline_inference/text_to_speech`](../../offline_inference/text_to_speech/README.md).
For the full list of supported architectures across all modalities, see
[Supported Models](../../../docs/models/supported_models.md).

## Supported Models

| Model | HuggingFace repo | Voice cloning | Streaming | Voice presets / upload | Gradio demo |
| --- | --- | --- | --- | --- | --- |
| Breeze-TTS-2 | `BreezeBlue/Breeze-TTS-2` | ✓ (`ref_audio`+`ref_text`) | ✓ (PCM stream) | speaker tags (`S0`..`S9`, default `S0`) | — |
| Audio8 TTS Preview | `Audio8/Audio8-TTS-Preview-0.6b` | ✓ (`ref_audio`+`ref_text`) | ✓ (PCM stream) | uploaded audio voice only; no presets | ✓ |
| Fish Speech S2 Pro | `fishaudio/s2-pro` | ✓ (`ref_audio`+`ref_text`) | ✓ (PCM stream) | — | ✓ |
| Gepard-1.0 | `nineninesix/gepard-1.0` | — (zero-shot default voice) | ✓ (PCM / WAV stream) | `default` only | — |
| GLM-TTS | `zai-org/GLM-TTS` | ✓ (`ref_audio`+`ref_text`, required) | ✓ (PCM stream) | — | ✓ |
| IndexTTS-2 | `IndexTeam/IndexTTS-2` | ✓ (`ref_audio` or uploaded `voice`) | `stream=true` response, non-chunk | uploaded audio voice only; no presets | — |
| IndexTTS-2.5 | native `checkpoints/` bundle | ✓ (`ref_audio` or uploaded `voice`) | `stream=true` response, non-chunk | uploaded audio voice only; no presets | — |
| Ming-omni-tts | `inclusionAI/Ming-omni-tts-0.5B` | ✓ (`ref_audio` / `speaker_embedding`) | ✓ (PCM stream) | IP labels + structured `instructions` | — |
| Ming-flash-omni-TTS | `Jonathan1909/Ming-flash-omni-2.0` | — (caption-controlled) | — | caption fields (`instructions`) | — |
| MOSS-TTS-Nano | `OpenMOSS-Team/MOSS-TTS-Nano` | ✓ (`ref_audio` required) | ✓ (PCM stream) | — | ✓ |
| OmniVoice | `k2-fsa/OmniVoice` | ✓ | — | — | — |
| Qwen3-TTS | `Qwen/Qwen3-TTS-12Hz-1.7B-{CustomVoice,VoiceDesign,Base}` | ✓ (Base) | ✓ (PCM + WebSocket) | ✓ (presets + `/v1/audio/voices` upload) | ✓ (standard + FastRTC) |
| VoxCPM2 | `openbmb/VoxCPM2` | ✓ | ✓ (AudioWorklet via gradio) | — | ✓ |
| dots.tts | `dots-studio/dots.tts-soar` | — (text-only) | ✓ (PCM stream) | — (default placeholder only) | — |
| Voxtral TTS | `mistralai/Voxtral-4B-TTS-2603` | ✓ (gated upstream) | ✓ | ✓ (presets) | ✓ |

CosyVoice3 is intentionally absent: no online example exists for it yet. See its [offline section](../../offline_inference/text_to_speech/README.md#cosyvoice3) instead.

## Common Quick Start

Launch the server (defaults shown — adjust `--port`, `--gpu-memory-utilization`, etc. as needed):

```bash
vllm serve <hf-repo-or-local-path> --omni --port 8091
```

Send a TTS request via curl. These generic snippets assume a model with a preset/default voice; voice-cloning-only models such as IndexTTS-2 require `ref_audio` or an uploaded audio `voice` (see model-specific sections below).

```bash
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Hello, how are you?",
        "voice": "default",
        "response_format": "wav"
    }' --output output.wav
```

Or via Python httpx:

```python
import httpx

response = httpx.post(
    "http://localhost:8091/v1/audio/speech",
    json={
        "input": "Hello, how are you?",
        "voice": "default",
        "response_format": "wav",
    },
    timeout=300.0,
)
open("output.wav", "wb").write(response.content)
```

Or via the OpenAI SDK:

```python
from openai import OpenAI

client = OpenAI(base_url="http://localhost:8091/v1", api_key="none")
response = client.audio.speech.create(
    model="<hf-repo>",
    voice="default",
    input="Hello, how are you?",
)
response.stream_to_file("output.wav")
```

Streaming PCM output (where supported) — set `stream=true`, `stream_format="audio"`, and `response_format="pcm"`:

```bash
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Hello, how are you?",
        "voice": "default",
        "stream": true,
        "stream_format": "audio",
        "response_format": "pcm"
    }' --no-buffer | play -t raw -r 24000 -e signed -b 16 -c 1 -
```

Adjust the player's sample rate to match the model (44.1 kHz for Fish Speech, 48 kHz for VoxCPM2, 22.05 kHz for Gepard and IndexTTS-2, and 24 kHz for many others).

For full request-shape documentation (all parameters, response formats, error codes), see the [Speech API reference](../../../docs/serving/speech_api.md).

---

## Gepard-1.0

Single-stage native AR TTS at 22.05 kHz mono. Zero-shot only: omit `voice` or pass `"default"`. Voice cloning from reference audio is not available yet.

### Prerequisites

Same NeMo NanoCodec install as the [offline Gepard section](../../offline_inference/text_to_speech/README.md#gepard-10). On a host whose CUDA toolkit cannot build kernels — no `nvcc`/`ninja`, or a consumer Blackwell (`sm_120`) card — also `export VLLM_USE_FLASHINFER_SAMPLER=0` before launch (same note as offline). That env is not a deploy-YAML field.

### Launch

```bash
vllm-omni serve nineninesix/gepard-1.0 --omni --port 8091 --trust-remote-code \
    --stage-init-timeout 900 \
    --deploy-config vllm_omni/deploy/gepard.yaml
# or:
./gepard/run_server.sh
```

`--stage-init-timeout 900` matches the online e2e fixture and the offline example. Serve defaults to 300s, which is often too short for a cold download of the talker plus NanoCodec.

The packaged `vllm_omni/deploy/gepard.yaml` must be passed with `--deploy-config`. The checkpoint self-identifies as `qwen3_5_text`, so omitting the YAML launches a diffusion fallback instead of the Gepard pipeline. The YAML sets `async_chunk: false`, `max_num_seqs: 4`, and currently pins `seed: 42`, so serving is deterministic by default until that YAML seed is removed. Pass an explicit per-request `seed` in tests and clients rather than depending on either default.

### Sending requests

```bash
python examples/online_serving/text_to_speech/gepard/speech_client.py \
    --text "Hello, this is Gepard speaking."

python examples/online_serving/text_to_speech/gepard/speech_client.py \
    --text "Hello, this is Gepard speaking." --seed 7 --stream --output output.pcm
```

### Notes

- Output: 22.05 kHz mono. `max_new_tokens` is a **frame** budget (1 token = 1 frame = 1024 samples ≈ 46.4 ms at 21.5 fps; adapter bounds 1..4096).
- Supported request fields: `input` (required), `voice` (`default` only), `response_format` (`wav` default; `wav/pcm/flac/mp3` non-streaming; `opus` 400 because 22.05 kHz is not an Opus sample rate; streaming `pcm/wav` only), `stream` / `stream_format`, `max_new_tokens`, `seed`.
- Unsupported: `speed`, `extra_params` (including `temperature`/`top_p`/`top_k`), `ref_audio`, `ref_text`, `speaker_embedding`, `task_type`, `instructions`, `language`, and `word_timestamps`.
- Concurrent requests at `max_num_seqs: 4` are supported. Native-AR recompute preemption is a known limitation of this architecture (a request that is preempted mid-generation can resume incorrectly); keep concurrency at or below `max_num_seqs` and treat preemption as out of scope until the platform fix lands.
- Optional comparison against the upstream Gepard reference server needs Blackwell/Hopper + CUDA 13 + Postgres and is not part of CI.

## dots.tts

Single-stage, text-only TTS at 48 kHz. The current integration supports
no-reference synthesis; voice cloning, reference audio, named voices, and
precomputed speaker embeddings are not supported yet.

### Launch

```bash
vllm serve dots-studio/dots.tts-soar --omni --trust-remote-code --port 8091
```

### Sending requests

```bash
# Non-streaming WAV
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Hello, this is a dots TTS online-serving test.",
        "voice": "default",
        "response_format": "wav"
    }' --output output.wav

# Streaming 48 kHz mono PCM
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Hello, this is a streaming dots TTS test.",
        "voice": "default",
        "stream": true,
        "stream_format": "audio",
        "response_format": "pcm"
    }' --no-buffer | play -t raw -r 48000 -e signed -b 16 -c 1 -
```

---

## GLM-TTS

2-stage TTS (AR + DiT flow-matching) at 24 kHz. Every request requires `ref_audio` + `ref_text`.

### Launch

```bash
vllm serve zai-org/GLM-TTS --omni --trust-remote-code --port 8091
# or:
bash examples/online_serving/text_to_speech/glm_tts/run_server.sh /path/to/GLM-TTS
```

### Sending requests

```bash
# Voice cloning (required)
python examples/online_serving/text_to_speech/glm_tts/openai_speech_client.py \
    --text "你好，这是语音克隆测试。" \
    --ref-audio file:///path/to/ref.wav \
    --ref-text "这是参考音频的文本内容。"

# Custom format
python examples/online_serving/text_to_speech/glm_tts/openai_speech_client.py \
    --text "Hello, this is a voice cloning test." \
    --ref-audio file:///path/to/ref.wav \
    --ref-text "Transcript of the reference audio." \
    --response-format mp3 -o output.mp3
```

### Gradio demo

```bash
bash examples/online_serving/text_to_speech/glm_tts/run_gradio_demo.sh
```

### Notes

- Output: 24 kHz mono WAV via HiFT vocoder.
- `ref_audio` + `ref_text` are **required** together on every request. Reference audio should be 3-10 seconds.
- Voice cloning feature extraction (WhisperVQ, CampPlus, mel) runs on the model side — no external dependency on the serving layer.

---

## IndexTTS-2 and IndexTTS-2.5

2-stage TTS at 22.05 kHz. Requests use `ref_audio` for voice cloning, or an uploaded audio `voice` from `/v1/audio/voices`. IndexTTS-2.5 uses a multilingual tokenizer, CAMPPlus speaker projection, EnhancedCodec, and code-only Stage 0→1 transfer by default. Both versions support emotion conditioning via `emo_audio`, `emo_text`, or `emo_vector` passed in `extra_params`.

### Prerequisites

IndexTTS-2 uses its existing frontend and does not require the IndexTTS-2.5 text dependencies. Before launching IndexTTS-2.5, install its optional frontend dependencies:

```bash
pip install 'vllm-omni[indextts2]'
```

### Launch

```bash
vllm serve IndexTeam/IndexTTS-2 --omni --trust-remote-code --port 8092
# or, to pass the bundled deploy config explicitly:
bash examples/online_serving/text_to_speech/indextts2/run_server.sh

# IndexTTS-2.5 default: use_gpt_latent=false
MODEL_VERSION=2.5 \
MODEL=/path/to/indextts-2.5 \
bash examples/online_serving/text_to_speech/indextts2/run_server.sh

```

### Sending requests

```bash
# Voice cloning (ref_audio required)
python examples/online_serving/text_to_speech/indextts2/speech_client.py \
    --text "你好，世界！" \
    --ref-audio /path/to/reference.wav

# With emotion audio
python examples/online_serving/text_to_speech/indextts2/speech_client.py \
    --text "今天心情很好！" \
    --ref-audio /path/to/ref.wav \
    --emo-audio /path/to/happy.wav

# IndexTTS-2.5 Japanese request
python examples/online_serving/text_to_speech/indextts2/speech_client.py \
    --model-version 2.5 \
    --model /path/to/indextts-2.5 \
    --lang ja \
    --text "こんにちは、音声合成のテストです。" \
    --ref-audio /path/to/ref.wav

# IndexTTS-2.5 native speed control
python examples/online_serving/text_to_speech/indextts2/speech_client.py \
    --model-version 2.5 \
    --model /path/to/indextts-2.5 \
    --speed 2.0 \
    --text "这是两倍速度的语音合成测试。" \
    --ref-audio /path/to/ref.wav
```

### Notes

- Output: 22.05 kHz mono WAV.
- Provide `ref_audio` on the documented raw request path, or pass `voice` only when it names an uploaded audio voice; neither version provides a built-in text-only preset voice.
- IndexTTS-2.5 request controls `lang` and `text_normalization` are carried in `extra_params`; the client does this for `--model-version 2.5`.
- IndexTTS-2.5 accepts the public `speed` request field in `[0.5, 2.0]`: `2.0` generates shorter, faster speech and `0.5` generates longer, slower speech. This is native Stage 1 duration control, so serving does not apply the generic playback-speed adjustment a second time. IndexTTS-2 does not use this control.
- IndexTTS-2.5 accepts language codes such as `zh`, `en`, `zhen` (mixed Chinese/English), `ja`, and `yue`. `Mandarin` is a vLLM-Omni convenience alias for `zh`. Japanese (`ja`) uses `fugashi` tokenization and produces audio, but it does not automatically expand numbers, dates, or percentages; callers should first write those inputs as readable Japanese text.
- A request `seed` controls Stage 0 AR sampling and per-request CFM noise. Different concurrent batch compositions do not guarantee a bit-identical waveform.
- IndexTTS-2.5 Stage 0 uses plain vLLM sampling and does not reproduce the official default `num_beams=3` beam search. For parity comparisons, run upstream with `num_beams=1`; output quality can differ from the official beam-search result.
- Emotion params (`emo_audio`, `emo_text`, `emo_vector`, `emo_alpha`, `use_emo_text`, `use_random`) are passed via the `extra_params` field. Official precedence is `use_emo_text` > `emo_vector` > `emo_audio` > same emotion as the speaker reference.
- IndexTTS-2.5 uses `vllm_omni/deploy/indextts2_5.yaml` with the official code-only Stage 0 to Stage 1 contract.
- For IndexTTS-2.5, set `MODEL` to the local native bundle; asset discovery accepts its nested `checkpoints/` layout.

---

## Audio8 TTS Preview

0.6B DualAR TTS at 44.1 kHz, 11 languages, zero-shot voice cloning.

### Prerequisites

None beyond the base install: the neural audio codec is implemented in tree and
its weights (`codec.pth`) ship with the checkpoint.

### Launch

```bash
vllm serve Audio8/Audio8-TTS-Preview-0.6b --omni --port 8092
# or:
./audio8_tts/run_server.sh
```

The deploy config auto-loads from `vllm_omni/deploy/audio8_tts.yaml` (HF
`model_type` is `arktts`). Do **not** pass `--trust-remote-code`: vllm-omni
registers its own `arktts` config, and transformers would otherwise prefer the
checkpoint's remote code and bypass it.

### Text-only synthesis

```bash
curl -X POST http://localhost:8092/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Welcome to Audio8 TTS.",
        "response_format": "wav"
    }' --output output.wav
```

### Voice cloning

```bash
curl -X POST http://localhost:8092/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Welcome to Audio8 TTS.",
        "ref_audio": "https://example.com/reference.wav",
        "ref_text": "The exact transcript of the reference recording."
    }' --output cloned.wav
```

`ref_audio` also accepts a `data:audio/wav;base64,...` URL. `ref_text` is
mandatory whenever `ref_audio` is present and must match the recording.
Uploading a voice via `POST /v1/audio/voices` lets the server reuse the encoded
reference codes across requests (`voice: "<name>"`).

### Streaming

```bash
python audio8_tts/speech_client.py --text "Welcome to Audio8 TTS." --stream --output out.pcm
ffplay -f s16le -ar 44100 -ac 1 out.pcm
```

### Gradio demo

```bash
./audio8_tts/run_gradio_demo.sh          # server + demo
python audio8_tts/gradio_demo.py --api-base http://localhost:8092   # demo only
```

### Benchmark

```bash
export VLLM_OMNI_BENCH_AUDIO_SAMPLE_RATE=44100   # required: harness defaults to 24 kHz
vllm bench serve --omni --host 127.0.0.1 --port 8092 \
    --model Audio8/Audio8-TTS-Preview-0.6b \
    --backend openai-audio-speech --endpoint /v1/audio/speech \
    --dataset-name seed-tts-text --dataset-path benchmarks/build_dataset/seed_tts_smoke \
    --seed-tts-locale en --num-prompts 20 --num-warmups 2 \
    --max-concurrency 1 --request-rate inf \
    --percentile-metrics ttft,e2el,audio_rtf,audio_ttfp,audio_duration,audio_underrun
```

Measured on 1x H20 **shared with an unrelated job holding ~80% SM**, so treat
these as a lower bound. 20 prompts from `seed_tts_smoke/en`, mean audio 4.5 s,
deploy defaults:

| | HF reference (batch=1) | vllm-omni c=1 | c=4 | c=8 |
| --- | --- | --- | --- | --- |
| RTF (mean) | 1.008 | **0.19** | 0.30 | 0.54 |
| Throughput (req/s) | 0.23 | 1.18 | 2.84 | **2.93** |
| E2E latency (mean, ms) | 4375 | 850 | 1349 | 2361 |
| Time to first packet (mean, ms) | n/a (no streaming) | 63 | 105 | 1124 |
| Underrun p99 / continuity OK | n/a | 0 s / 100% | 0 s / 100% | 0 s / 100% |

~5.3x lower per-request RTF than the upstream reference implementation at
concurrency 1, ~12.8x aggregate throughput at concurrency 8.

#### Stage-0 `max_num_seqs`: first-packet vs throughput

This subsection is operator tuning guidance, not a claim this PR optimizes
anything: the shipped deploy default is unchanged (`max_num_seqs: 4`). The
numbers below are a single run on the same contended H20 as above (one unrelated
job holding ~80% SM, no repeats), so read them as directional, not as measured
speedups. Same setup, varying stage 0's `max_num_seqs` (stage 1 stays at 1):

| stage-0 `max_num_seqs` | client concurrency | req/s | RTF | TTFP mean / p99 (ms) | underrun p99 (s) |
| --- | --- | --- | --- | --- | --- |
| 4 (default) | 1 | 1.18 | 0.19 | 63 / 67 | 0.00 |
| 4 | 4 | 2.84 | 0.30 | 105 / 148 | 0.00 |
| 4 | 8 | 2.93 | 0.54 | 1124 / 1642 | 0.00 |
| 8 | 1 | 1.16 | 0.19 | 64 / 70 | 0.00 |
| 8 | 4 | 2.88 | 0.30 | 107 / 148 | 0.00 |
| 8 | 8 | **3.72** | 0.40 | **247** / 733 | 0.22 |
| 8 | 16 | 3.91 | 0.65 | 1366 / 2530 | 0.29 |

Reading of this:

- Below the limit (`concurrency <= max_num_seqs`) the setting is irrelevant, as
  expected — c=1 and c=4 are identical for both.
- At c=8, raising the limit to 8 admits every request instead of queueing half
  of them: in this single run, roughly +27% throughput and ~4.5x lower
  first-packet latency.
- Throughput saturates around 3.7-3.9 req/s (~17 s of audio per second). Past
  c=8 you only buy queueing delay.
- The cost of admitting more streams is a 0.22-0.29 s worst-case buffer deficit
  in 1 of 20 requests (`Streaming continuity OK rate` 95%), because stage 1 runs
  `max_num_seqs: 1` and the codec window round-robins across streams. Client-side
  prebuffering (the bundled Gradio demo holds 2 chunks) absorbs that; raising
  stage 1's `max_num_seqs` is the untested knob if you need both.

The shipped default stays at 4 because every measured point there had zero
underrun. Raise it to 8 if first-packet latency under load matters more than a
rare sub-300 ms gap.

### Notes

- Output: 44.1 kHz mono; ~21.5 codec frames per second.
- No built-in speaker presets. Omit `voice` for a random timbre, or clone one.
- `max_new_tokens` caps generated codec frames (1 frame ~= 46 ms).
- Context is 2048 packed text+audio positions (`max_model_len: 2048`).
- Do not send `temperature: 0`: greedy decoding is degenerate for this
  checkpoint and truncates the utterance. The deploy defaults
  (0.7 / top_k 50 / top_p 0.9) mirror `generation_config.json`.

---

## Fish Speech S2 Pro

4B dual-AR TTS at 44.1 kHz. Server uses the DAC codec, which is vendored in
vLLM-Omni (no extra packages required).

### Kvcache attention fast path

Fish Speech S2 Pro uses a Triton decode-only kvcache attention fast path by
default on CUDA builds. Set `VLLM_OMNI_FISH_KVCACHE_ATTN=0` to disable it, or
`VLLM_OMNI_FISH_KVCACHE_ATTN=required` to fail fast if the fast path cannot be
installed.

```bash
# Verify fast path availability.
python - <<'PY'
from vllm_omni.attention import fish_kvcache_attn

print(fish_kvcache_attn.is_available())
print(fish_kvcache_attn.load_error())
PY

# Optional: disable the runtime fast path.
export VLLM_OMNI_FISH_KVCACHE_ATTN=0
```

### Launch

```bash
vllm serve fishaudio/s2-pro --omni --port 8091
# or:
./fish_speech/run_server.sh
```

The deploy config auto-loads from `vllm_omni/deploy/fish_qwen3_omni.yaml` (the HF `model_type` on the fishaudio checkpoint is `fish_qwen3_omni`).

### Voice cloning

```bash
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Hello, this is a cloned voice.",
        "voice": "default",
        "ref_audio": "https://example.com/reference.wav",
        "ref_text": "Transcript of the reference audio."
    }' --output cloned.wav
```

### CLI client

```bash
cd examples/online_serving/text_to_speech/fish_speech
python speech_client.py --text "Hello, how are you?"
python speech_client.py --text "Hello world" --stream --output output.pcm
```

### Gradio demo

```bash
./fish_speech/run_gradio_demo.sh             # launches server + Gradio
python fish_speech/gradio_demo.py --api-base http://localhost:8091  # if server already running
```

### Notes

- Output: 44.1 kHz mono.
- Streaming PCM player command must use `-r 44100`.

---

## Ming-omni-tts

Dense 0.5B two-stage TTS served through `/v1/audio/speech`. Ming uses the standard speech endpoint plus structured controls in `instructions`, `voice`, `language`, `ref_audio`, `ref_text`, and `speaker_embedding`.

### Launch

```bash
bash examples/online_serving/text_to_speech/ming_tts/run_server.sh
```

Equivalent manual command:

```bash
vllm-omni serve inclusionAI/Ming-omni-tts-0.5B \
    --deploy-config vllm_omni/deploy/ming_tts.yaml \
    --host 0.0.0.0 --port 8091 \
    --enforce-eager --omni
```

### Sending requests

```bash
python examples/online_serving/text_to_speech/ming_tts/openai_speech_client.py \
    --text "你好，这是 Ming 在线语音合成测试。"
```

Structured dialect control:

```bash
python examples/online_serving/text_to_speech/ming_tts/openai_speech_client.py \
    --text "我觉得社会企业同个人都有责任" \
    --instruction-json '{"方言":"广粤话"}' \
    --ref-audio /path/to/yue_prompt.wav
```

Zero-shot cloning:

```bash
python examples/online_serving/text_to_speech/ming_tts/openai_speech_client.py \
    --text "我们的愿景是构建未来服务业的数字化基础设施，为世界带来更多微小而美好的改变。" \
    --ref-audio /path/to/10002287-00000094.wav \
    --ref-text "在此奉劝大家别乱打美白针。"
```

### Notes

- `run_curl.sh` keeps a small sanity subset; use the Ming README for the broader request cookbook.
- Online serving is speech-shaped today; music-only `bgm` and text-to-audio `tta` remain offline examples.
- Full request details live in [`ming_tts/README.md`](ming_tts/README.md).

---

## Ming-flash-omni-TTS

Standalone talker-only deployment of Ming-flash-omni-2.0. Voice is controlled through caption text passed via `instructions`.

### Launch

```bash
# from repo root
bash examples/online_serving/text_to_speech/ming_flash_omni_tts/run_server.sh
```

Equivalent manual command:

```bash
vllm serve Jonathan1909/Ming-flash-omni-2.0 \
    --deploy-config vllm_omni/deploy/ming_flash_omni_tts.yaml \
    --host 0.0.0.0 --port 8091 \
    --trust-remote-code --omni
```

### Sending requests

```bash
python examples/online_serving/text_to_speech/ming_flash_omni_tts/speech_client.py \
    --text "我们当迎着阳光辛勤耕作，去摘取，去制作，去品尝，去馈赠。" \
    --output ming_online.wav
```

ASMR-style caption via `instructions`:

```bash
python examples/online_serving/text_to_speech/ming_flash_omni_tts/speech_client.py \
    --text "我会一直在这里陪着你，直到你慢慢、慢慢地沉入那个最温柔的梦里……好吗？" \
    --instructions "这是一种ASMR耳语，属于一种旨在引发特殊感官体验的创意风格。这个女性使用轻柔的普通话进行耳语，声音气音成分重。" \
    --output ming_online_asmr.wav
```

### Notes

- Server uses `use_zero_spk_emb=True` and the cookbook decode defaults (`max_decode_steps=200`, `cfg=2.0`, `sigma=0.25`, `temperature=0.0`). For other caption fields (`语速`, `基频`, `IP`, BGM, etc.) or overriding decode args, use the offline example where `additional_information` is set explicitly.
- This is the online counterpart of [`examples/offline_inference/text_to_speech/ming_flash_omni_tts/`](../../offline_inference/text_to_speech/ming_flash_omni_tts/).
- For multimodal Ming-flash-omni online serving, see [`examples/online_serving/ming_flash_omni/`](../../ming_flash_omni/).

---

## MOSS-TTS Local Transformer v1.5

For a single H200, the optional
[`moss_tts_local_h200.yaml`](../../../vllm_omni/deploy/moss_tts_local_h200.yaml)
deployment places both the talker and codec on logical GPU 0:

```bash
CUDA_VISIBLE_DEVICES=0 VLLM_OMNI_EVENT_DRIVEN_ORCH=1 \
    vllm serve OpenMOSS-Team/MOSS-TTS-Local-Transformer-v1.5 \
    --omni --trust-remote-code \
    --deploy-config vllm_omni/deploy/moss_tts_local_h200.yaml \
    --disable-log-stats
```

Run from the repository root and select an available physical GPU with
`CUDA_VISIBLE_DEVICES`. The command enables event-driven orchestration and
disables detailed per-request statistics logging to reduce CPU overhead at
high concurrency. Remove `--disable-log-stats` when those statistics are needed;
keep these settings identical when comparing performance.
This preset configures 256 request slots per stage,
a 32 GiB talker KV cache, talker CUDA Graph buckets through 512 scheduled tokens,
and codec batch buckets through 256. It requires more than 80 GiB of GPU memory;
request capacity also depends on input and generated lengths. The default
[`moss_tts_local.yaml`](../../../vllm_omni/deploy/moss_tts_local.yaml) remains
available for smaller deployments.

The preset enables the optional codec backend with
`hf_overrides.codec_attention_backend: triton` on stage 1. It preserves the
streaming ring-cache mask and uses BF16 attention with 64-dimensional heads;
other attention shapes use PyTorch SDPA. Set the backend to `sdpa` to use the
default attention implementation. Codec terminal tails share execution only
when they already map to the same padded CUDA Graph; returned audio retains
each request's actual length.

Voice cloning requests use `ref_audio` and `ref_text`. For streaming output,
set `stream: true`, `stream_format: "audio"`, and `response_format: "pcm"`;
the native PCM format is 48 kHz, stereo, signed 16-bit little-endian. Compute
audio throughput as `PCM bytes / (48000 * 2 * 2) / elapsed seconds`, and compare
the same requests, concurrency, and reference-cache state.

## MOSS-TTS-Nano

Single-stage 0.1B AR LM + MOSS-Audio-Tokenizer-Nano codec at 48 kHz mono. Every request must include `ref_audio`; there are no built-in speaker presets.

> The OpenAI-schema `voice` and `ref_text` fields are accepted but ignored — `voice_clone` does not consume a transcript, and upstream's `continuation` mode (the only path that accepts `prompt_text`) emits near-silent output, so it is not exposed here. Sample reference clips ship in the upstream repo under [`assets/audio/`](https://github.com/OpenMOSS/MOSS-TTS-Nano/tree/main/assets/audio).

### Launch

```bash
vllm serve OpenMOSS-Team/MOSS-TTS-Nano --omni --port 8091
# or:
./moss_tts_nano/run_server.sh
```

The deploy config at `vllm_omni/deploy/moss_tts_nano.yaml` auto-loads; no `--deploy-config`, `--trust-remote-code`, or `--enforce-eager` flags are needed.

### Sending requests

```bash
# One-off fetch of a sample reference clip; cache under XDG_CACHE_HOME.
REF_DIR="${XDG_CACHE_HOME:-$HOME/.cache}/moss-tts-nano"
mkdir -p "$REF_DIR"
REF_WAV="$REF_DIR/zh_1.wav"
[ -s "$REF_WAV" ] || curl -L -o "$REF_WAV" https://raw.githubusercontent.com/OpenMOSS/MOSS-TTS-Nano/main/assets/audio/zh_1.wav
REF_AUDIO=$(base64 -w 0 "$REF_WAV")

curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d "{
        \"input\": \"你好，这是语音合成测试。\",
        \"ref_audio\": \"data:audio/wav;base64,${REF_AUDIO}\",
        \"response_format\": \"wav\"
    }" --output output.wav
```

### Streaming PCM

```bash
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d "{
        \"input\": \"Hello, streaming output from MOSS-TTS-Nano.\",
        \"ref_audio\": \"data:audio/wav;base64,${REF_AUDIO}\",
        \"stream\": true,
        \"stream_format\": \"audio\",
        \"response_format\": \"pcm\"
    }" --no-buffer | play -t raw -r 48000 -e signed -b 16 -c 1 -
```

### Gradio demo

```bash
# Option 1: launch server + Gradio together
./moss_tts_nano/run_gradio_demo.sh

# Option 2: server already running
python moss_tts_nano/gradio_demo.py --api-base http://localhost:8091
```

Then open <http://localhost:7860> in your browser.

### Notes

- Output is 48 kHz mono PCM (the upstream tokenizer is internally stereo at 48 kHz; the wrapper averages to mono before reaching the engine).
- Standard `/v1/audio/speech` request shape: `input`, `ref_audio` (base64 data URL), `response_format`, `stream`, `max_new_tokens`. The `voice` and `ref_text` fields from the OpenAI schema are accepted but ignored.

---

## OmniVoice

Zero-shot multilingual TTS (600+ languages). Online serving currently exposes **auto voice** only; voice cloning and voice design are available offline.

### Prerequisites

```bash
huggingface-cli download k2-fsa/OmniVoice
```

Voice cloning (offline) needs `transformers>=5.3.0`; auto voice works with `transformers>=4.57.0`.

### Launch

```bash
vllm serve k2-fsa/OmniVoice --omni --port 8091 --trust-remote-code
# or:
./omnivoice/run_server.sh
```

### CLI client

```bash
cd examples/online_serving/text_to_speech/omnivoice
# Text-only (auto voice)
python speech_client.py --text "Hello, how are you?"

# Language hint
python speech_client.py --text "Bonjour, comment allez-vous?" --language French
# Voice cloning (reference audio + optional ref_text)
python speech_client.py \
--text "Bonjour, comment allez-vous?" \
--ref-audio /path/to/ref_audio.wav \
--ref-text "Bonjour, comment allez-vous?"

# Style instruction (voice design-style control)
python speech_client.py \
--text "Bonjour, comment allez-vous?" \
--language French \
--instructions "loud voice"

# Deterministic output with seed parameter
python speech_client.py --text "Hello, how are you?" --seed 42
```

The client supports `--api-base`, `--model`, `--text`, `--response-format`, `--language`, `--voice`, `--ref-audio`, `--ref-text`, `--instructions`, `--seed`, and `--output`.

## Qwen3-TTS

Three model variants exposed via separate checkpoints:

| Variant | HF repo | Use |
| --- | --- | --- |
| CustomVoice | `Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice` | Predefined speakers (`vivian`, `ryan`, …) with optional style instructions |
| VoiceDesign | `Qwen/Qwen3-TTS-12Hz-1.7B-VoiceDesign` | Natural-language voice style description |
| Base | `Qwen/Qwen3-TTS-12Hz-1.7B-Base` | Voice cloning from a reference audio |

Each variant ships smaller `0.6B` companions where available.

### Launch

```bash
vllm serve Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice --omni --port 8091
# or:
./qwen3_tts/run_server.sh                # default: CustomVoice
./qwen3_tts/run_server.sh VoiceDesign
./qwen3_tts/run_server.sh Base
```

For a local deployment with multiple API frontend processes sharing one set
of TTS stage engines, add `--api-server-count`:

```bash
vllm serve Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice \
    --omni --api-server-count 2 --port 8091
```

This mode supports local EngineCore stages only; headless or remote stage
deployments are not supported. Runtime voice upload and deletion are disabled
with multiple API frontends because their registries are process-local.
Built-in voices, inline `ref_audio`, and voices restored from `custom_voice_dir`
at startup are supported.

### Executor backend

Single-GPU serves now default to the uniproc executor (lower IPC overhead, the Base cloning use case from [#2603](https://github.com/vllm-project/vllm-omni/issues/2603) / [#2604](https://github.com/vllm-project/vllm-omni/pull/2604)). `vllm_omni/deploy/qwen3_tts.yaml` is the only Qwen3-TTS deploy config; pass `--deploy-config <path>` to override.

To opt out of chunked streaming, pass `--no-async-chunk` — the pipeline auto-dispatches to the end-to-end codec processor.

### Sending requests

```bash
# CustomVoice with a predefined speaker
python qwen3_tts/openai_speech_client.py \
    --model Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice \
    --text "今天天气真好" \
    --speaker ryan \
    --instructions "用开心的语气说"

# VoiceDesign with a style description
python qwen3_tts/openai_speech_client.py \
    --model Qwen/Qwen3-TTS-12Hz-1.7B-VoiceDesign \
    --task-type VoiceDesign \
    --text "哥哥，你回来啦" \
    --instructions "体现撒娇稚嫩的萝莉女声，音调偏高"

# Base voice cloning
python qwen3_tts/openai_speech_client.py \
    --model Qwen/Qwen3-TTS-12Hz-1.7B-Base \
    --task-type Base \
    --text "Hello, this is a cloned voice" \
    --ref-audio /path/to/reference.wav \
    --ref-text "Original transcript of the reference audio"
```

### Voices endpoint

List available voices, or upload a custom one for Base cloning:

```bash
# List
curl http://localhost:8091/v1/audio/voices

# Upload
curl -X POST http://localhost:8091/v1/audio/voices \
    -F "audio_sample=@/path/to/voice_sample.wav" \
    -F "consent=user_consent_id" \
    -F "name=custom_voice_1" \
    -F "ref_text=The exact transcript of the audio sample." \
    -F "speaker_description=warm narrator"
```

For Qwen3-TTS, uploaded voices are Base voice-cloning inputs and require a Base
checkpoint. When a request names an uploaded voice, the server infers
`task_type="Base"`. Built-in presets such as `vivian` and `ryan` remain
CustomVoice speakers and require a CustomVoice checkpoint.

The runtime upload and delete routes require a single API frontend; with
`--api-server-count > 1`, use inline `ref_audio` or restore precomputed voices
from `custom_voice_dir` at startup.

### Precomputed custom voices

For reused Base voice-cloning speakers, precompute the reference artifacts once
and load them at server startup. Precomputed voices use the same Base task and
checkpoint-matching rules as uploaded voices:

```bash
python qwen3_tts/precompute_custom_voice.py \
    --model Qwen/Qwen3-TTS-12Hz-1.7B-Base \
    --voice-name alice \
    --ref-audio /path/to/reference.wav \
    --ref-text "Original transcript of the reference audio" \
    --mode icl \
    --output-dir /path/to/custom_voices
```

`--mode icl` stores both `speaker_embedding` and `ref_code`; `--mode xvec` stores only the speaker embedding. Add the output directory to a deploy config:

```yaml
custom_voice_dir: /path/to/custom_voices
```

Then start the server with that config and call the Speech API with only the voice name:

```bash
vllm serve Qwen/Qwen3-TTS-12Hz-1.7B-Base --omni --deploy-config /path/to/qwen3_tts_custom_voice.yaml

curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{"input":"Hello from a precomputed voice.","voice":"alice","task_type":"Base"}' \
    --output alice.wav
```

### Streaming PCM

```bash
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Hello, how are you?",
        "voice": "vivian",
        "language": "English",
        "stream": true,
        "stream_format": "audio",
        "response_format": "pcm"
    }' --no-buffer | play -t raw -r 24000 -e signed -b 16 -c 1 -
```

Raw PCM streaming requires `stream_format="audio"`, `response_format="pcm"`, and `async_chunk: true` in the deploy config (default in `qwen3_tts.yaml`). `speed` is not supported when streaming.

### Streaming WebSocket

The `/v1/audio/speech/stream` endpoint accepts text incrementally and, by default, synthesizes the buffered text as one continuous request on `input.done`:

```bash
python qwen3_tts/streaming_speech_client.py --text "Hello world. How are you? I am fine."
python qwen3_tts/streaming_speech_client.py --text "..." --simulate-stt --stt-delay 0.1
```

For per-sentence audio (including Indic danda `।`) before `input.done`:

```bash
python qwen3_tts/streaming_speech_client.py \
    --text "नमस्ते। कैसे हो?" \
    --split-granularity sentence
```

`input.done` flushes without closing, so repeating `--text` synthesizes several utterances over one connection:

```bash
python qwen3_tts/streaming_speech_client.py \
    --text "First utterance." \
    --text "Second utterance, same connection."
```

To receive word-level timestamps, launch the server with a forced aligner:

```bash
vllm-omni serve Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice \
    --omni \
    --deploy-config vllm_omni/deploy/qwen3_tts.yaml \
    --trust-remote-code \
    --forced-aligner Qwen/Qwen3-ForcedAligner-0.6B
```

Then request PCM JSON sidecar chunks:

```bash
python qwen3_tts/streaming_speech_client.py \
    --text "Hello world. How are you?" \
    --stream-audio \
    --response-format pcm \
    --word-timestamps
```

The client writes one PCM file per sentence and a matching
`sentence_XXX_timestamps.json` sidecar.

Non-streaming requests can also ask for timestamps: pass
`"word_timestamps": true` to `POST /v1/audio/speech` and read the
`X-Word-Timestamps` response header (JSON list of `{word, start_ms, end_ms}`,
ASCII-escaped). Past 4 KB the header is replaced by
`X-Word-Timestamps-Omitted: oversize; bytes=<n>; limit=4096` and the audio
still returns — use the WebSocket path for long transcripts.

To *see* the alignment instead of reading a JSON sidecar, run the
word-timestamp Gradio demo (server must be launched with `--forced-aligner`):

```bash
python qwen3_tts/word_timestamps_demo.py --api-base http://localhost:8091
```

Each sentence's audio plays in an `<audio>` element while its text is rendered
as inline word spans; the current word highlights as `audio.currentTime`
crosses each `start_ms`. The **Stop (barge-in)** button cuts playback and
reports the last-spoken word, useful for the voice-agent barge-in case.

### Gradio demos

```bash
./qwen3_tts/run_gradio_demo.sh                              # CustomVoice (default)
./qwen3_tts/run_gradio_demo.sh --task-type VoiceDesign
./qwen3_tts/run_gradio_demo.sh --task-type Base
```

### Speaker embedding interpolation

`qwen3_tts/speaker_embedding_interpolation.py` blends two predefined speakers' embeddings to produce intermediate voices. See the script for usage.

### Batch client

`qwen3_tts/batch_speech_client.py` issues many concurrent requests for throughput measurement.

### Notes

- Base voice cloning has uniproc-vs-mp tradeoffs depending on per-request reference audio cost; see the executor-backend section above.
- With async chunking, Qwen3-TTS Base voice cloning sends the full reference context in the first Code2Wav packet, then caches that prefix on the Code2Wav stage for follow-up chunks in the same request.
- `vllm_omni/deploy/qwen3_tts.yaml` is the default deploy config (loaded by HF `model_type`); per-stage runtime overrides are available via `--stage-N-<field> <value>`.

---

## VoxCPM2

Single-stage native AR TTS at 48 kHz.

### Launch

```bash
vllm serve openbmb/VoxCPM2 --omni --host 0.0.0.0 --port 8000
```

Deploy config auto-loads from `vllm_omni/deploy/voxcpm2.yaml`. Pass `--deploy-config <path>` to override or `--stage-N-<field> <value>` for per-stage runtime tweaks.

### Sending requests

```bash
# Zero-shot synthesis
python voxcpm2/openai_speech_client.py --text "Hello, this is VoxCPM2."

# Voice cloning
python voxcpm2/openai_speech_client.py \
    --text "This should sound like the reference speaker." \
    --ref-audio /path/to/reference.wav
```

The `ref_audio` field accepts local file paths (auto-base64), HTTP URLs, or `data:audio/wav;base64,...` data URIs.

### Precomputed custom voices

For repeated VoxCPM2 speakers, precompute the prompt cache and load it through `custom_voice_dir`:

```bash
python voxcpm2/precompute_custom_voice.py \
    --model openbmb/VoxCPM2 \
    --voice-name alice \
    --ref-audio /path/to/reference.wav \
    --mode ref_continuation \
    --prompt-text "Original transcript of the reference audio" \
    --output-dir /path/to/custom_voices
```

Add the output directory to the deploy config:

```yaml
custom_voice_dir: /path/to/custom_voices
```

After startup, `/v1/audio/voices` lists `alice`, and `/v1/audio/speech` can use `voice="alice"` without sending `ref_audio`.

### Gradio demo (gapless streaming via AudioWorklet)

```bash
python voxcpm2/gradio_demo.py
```

Uses an AudioWorklet-based player adapted from the Qwen3-TTS demo for gap-free playback. Raw PCM audio is streamed from the OpenAI Speech endpoint with `stream=true` and `stream_format="audio"`.

---

## Voxtral TTS

Voxtral-4B-TTS (Mistral). Uses the `mistral_common` `SpeechRequest` protocol; voice presets are model-specific.

### Prerequisites

Latest `mistral_common` with `SpeechRequest` support:

```bash
pip install -e /path/to/mistral-common  # or upgrade from PyPI when available
```

### Launch

```bash
vllm serve mistralai/Voxtral-4B-TTS-2603 --omni --port 8091
```

Deploy config auto-loads from `vllm_omni/deploy/voxtral_tts.yaml`.

### Gradio demo

```bash
python voxtral_tts/gradio_demo.py
```

The demo handles voice-preset selection and reference-audio upload. `voxtral_tts/text_preprocess.py` provides the text-normalization helpers used by the demo (also available for other clients).

### Notes

- Voice presets are listed on the HF model card (`mistralai/Voxtral-4B-TTS-2603`).
- Voice cloning is gated upstream and may require a recent `mistral_common`.
- A standalone CLI client is not yet shipped; the gradio demo is the canonical reference for now.

## Breeze-TTS-2

Two-stage AR TTS (T5Gemma2 + Qwen3 talker with a depth decoder → bundled Qwen3-TTS codec) at 24 kHz mono, from [BreezeBlue](https://huggingface.co/BreezeBlue/Breeze-TTS-2). Four modes are selected automatically from the request fields: plain (`input`), voice design (`instructions`), clone (`ref_audio`+`ref_text`), and voice direction (reference trio + `instructions`).

### Launch

```bash
vllm serve BreezeBlue/Breeze-TTS-2 --omni --port 8091
# or:
./breeze_tts_2/run_server.sh
```

The deploy config at `vllm_omni/deploy/breeze_tts_2.yaml` auto-loads (async-chunk streaming, 8-frame inter-stage chunks).

### Sending requests

```bash
# Plain synthesis (speaker tags S0..S9, default S0)
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Hello, this is Breeze TTS 2 on vLLM-Omni.",
        "voice": "S0",
        "response_format": "wav",
        "sample_rate": 24000
    }' --output breeze_plain.wav

# Voice direction (clone a reference, then steer the delivery)
curl -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "We need to discuss what happened last night.",
        "ref_audio": "file:///path/to/reference.wav",
        "ref_text": "The exact transcript of the reference audio.",
        "instructions": "Speak slowly with a restrained, serious tone.",
        "response_format": "wav"
    }' --output breeze_direction.wav
```

### Streaming PCM

```bash
curl -N -X POST http://localhost:8091/v1/audio/speech \
    -H "Content-Type: application/json" \
    -d '{
        "input": "Streaming output from Breeze TTS 2.",
        "stream": true,
        "stream_format": "audio",
        "response_format": "pcm",
        "sample_rate": 24000
    }' --output breeze_stream.pcm
```

### Notes

- Only `sample_rate=24000` is accepted; `speed` must be `1.0`.
- `guidance_scale`/`cfg_scale` must be `1.0`; `negative_prompt` is rejected (CFG companion support is a follow-up).
- `instructions` without `ref_audio` is voice design; with `ref_audio`+`ref_text` it is voice direction.
- See [`recipes/BreezeBlue/Breeze-TTS-2.md`](../../../recipes/BreezeBlue/Breeze-TTS-2.md) for the full recipe and the offline example under [`examples/offline_inference/text_to_speech/breeze_tts_2/`](../../offline_inference/text_to_speech/breeze_tts_2/).