# ACE Step Audio Outpaint API

> 既存の音声クリップの前後に、新たに作曲した音楽を追加して拡張します

`audio_url` で提供されたトラックを継続します。`extend_before_duration` と `extend_after_duration` はそれぞれ先頭または末尾に最大 107 秒追加でき、デフォルトでは末尾に 30 秒追加します。スタイルは `tags` で指定し、追加部分には任意で `lyrics` を指定できます。ステップ数、スケジューラー、ガイダンス設定は他の ACE Step モデルと同じです。

- Model id: `ace-step/audio-outpaint`
- Made by: ACE Studio
- Category: Text to Music
- Output: audio
- Price per second of your output audio: $0.0002 / second of output audio (cheapest run $0.001 (1 API credit))
- Run: `POST https://api.doitong.com/v1/run/ace-step/audio-outpaint`
- Quote: `POST https://api.doitong.com/v1/quote/ace-step/audio-outpaint`
- Docs page: https://doitong.com/ja/developers/models/ace-step/audio-outpaint

## Pricing

Price: **$0.0002 / second of output audio**. Price per second of your output audio: the input files are measured before the run (length, resolution, frame rate). The quote measures the same files and is exactly what the run charges.

The full example input below costs $0.006 = 6 API credits (30 s output audio × $0.0002).

Prices are the upstream price in USD, paid from the API balance in API credits (1000 API credits = 1 USD). `POST https://api.doitong.com/v1/quote/ace-step/audio-outpaint` with the same JSON body returns the exact price for that input; the quote is exactly what a run charges. Invalid input is never charged and failed or canceled requests are refunded automatically.

## Input parameters

Send either the canonical name or the native field name (not both). Canonical names are the same across models.

| Parameter | Canonical name | Type | Required | Default | Allowed values / range | Description |
|---|---|---|---|---|---|---|
| `audio_url` | `audio` | string (audio URL) | yes |  |  | アウトペインティング用の音声ファイル URL。 |
| `extend_before_duration` |  | number | no | `0` | 0 – 107 | 音声の開始前に追加する拡張部分の長さ（秒）。 |
| `extend_after_duration` |  | number | no | `30` | 0 – 107 | 音声の終了後に追加する拡張部分の長さ（秒）。 |
| `tags` |  | string | yes |  |  | カンマ区切りのジャンルとして指定する音声スタイルタグ。代替手段として `prompt` でも指定できます。 |
| `lyrics` |  | string | no | `` |  | 歌唱する歌詞。セクションは [verse]、[chorus]、[bridge] などのコントロールで構成します。歌詞のない音声では、この入力を省略するか、[inst] または [instrumental] のみを指定してください。 |
| `number_of_steps` |  | integer | no | `27` | 3 – 60 | 音声生成時に使用するステップ数。 |
| `seed` |  | integer \| null | no |  |  | 再現可能な生成に使用するシード。値を指定しない場合はランダムに選択されます。 |
| `scheduler` |  | enum (string) | no | `euler` | `euler`, `heun` | 生成時に使用するスケジューラー。 |
| `guidance_type` |  | enum (string) | no | `apg` | `cfg`, `apg`, `cfg_star` | 生成時に使用する CFG タイプ。 |
| `granularity_scale` |  | integer | no | `10` | -100 – 100 | 生成時に適用する粒度スケール。増加させるとアーティファクトが減少する場合があります。 |
| `guidance_interval` |  | number | no | `0.5` | 0 – 1 | ガイダンスを適用する生成スケジュールの範囲。0.5 を選ぶと、infer_steps の 0.25 * から 0.75 * までのステップに制限され、開始部分と終了部分にはガイダンスが適用されません。 |
| `guidance_interval_decay` |  | number | no | `0` | 0 – 1 | 生成区間内のガイダンス減衰。0.0 では減衰を無効にし、それ以外では、その区間でスケールを guidance_scale から min_guidance_scale まで減少させます。 |
| `guidance_scale` |  | number | no | `15` | 0 – 200 | 生成時に適用するガイダンスのスケール。 |
| `minimum_guidance_scale` |  | number | no | `3` | 0 – 200 | 生成中の減衰後に到達する最低ガイダンススケール。 |
| `tag_guidance_scale` |  | number | no | `5` | 0 – 10 | 生成時に適用するタグガイダンスのスケール。 |
| `lyric_guidance_scale` |  | number | no | `1.5` | 0 – 10 | 生成時に適用する歌詞ガイダンスのスケール。 |

File parameters (`audio`) take a public `https://` URL, a `data:` URI up to 10 MB, or the `file_url` of an upload from `POST /files`.

## Example input

Required parameters only:

```json
{
  "tags": "lofi, hiphop, drum and bass, trap, chill",
  "audio": "https://content.doitong.com/audio/showcase/v3/tools/dub_es.mp3"
}
```

A fuller example:

```json
{
  "tags": "lofi, hiphop, drum and bass, trap, chill",
  "audio_url": "https://content.doitong.com/audio/showcase/v3/tools/dub_es.mp3"
}
```

## Run it

Set `DOITONG_API_KEY` to a key from https://doitong.com/developers/dashboard#keys. `?wait=20` returns the finished request in the same call when it is ready within 20 seconds; otherwise poll `GET /requests/{id}` (it also accepts `?wait=`), or pass `webhook_url`.

### curl

```bash
# Run the model; wait up to 20 s for the finished result in the same call
curl -X POST "https://api.doitong.com/v1/run/ace-step/audio-outpaint?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "tags": "lofi, hiphop, drum and bass, trap, chill",
    "audio_url": "https://content.doitong.com/audio/showcase/v3/tools/dub_es.mp3"
  }'

# Still "queued" or "running"? Poll with the id from the response:
curl "https://api.doitong.com/v1/requests/REQUEST_ID?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY"
```

### JavaScript

```javascript
const API = "https://api.doitong.com/v1";
const headers = {
  "Authorization": "Bearer " + process.env.DOITONG_API_KEY,
  "Content-Type": "application/json",
};

// Run the model; wait up to 20 s for the finished result in the same call
let res = await fetch(API + "/run/ace-step/audio-outpaint?wait=20", {
  method: "POST",
  headers,
  body: JSON.stringify({
    "tags": "lofi, hiphop, drum and bass, trap, chill",
    "audio_url": "https://content.doitong.com/audio/showcase/v3/tools/dub_es.mp3"
  }),
});
let request = await res.json();
if (!res.ok) throw new Error(request.error.code + ": " + request.error.message);

// Not finished yet: long-poll until it is
while (request.status === "queued" || request.status === "running") {
  res = await fetch(API + "/requests/" + request.id + "?wait=20", { headers });
  request = await res.json();
}
if (request.status !== "succeeded") throw new Error(JSON.stringify(request.error));
console.log(request.outputs.map((o) => o.url), request.cost.credits + " API credits ($" + request.cost.usd + ")");
```

### Python

```python
import os
import requests

API = "https://api.doitong.com/v1"
headers = {"Authorization": "Bearer " + os.environ["DOITONG_API_KEY"]}

payload = {
    "tags": "lofi, hiphop, drum and bass, trap, chill",
    "audio_url": "https://content.doitong.com/audio/showcase/v3/tools/dub_es.mp3",
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/ace-step/audio-outpaint", params={"wait": 20}, json=payload, headers=headers)
request = r.json()
if not r.ok:
    raise RuntimeError(request["error"]["code"] + ": " + request["error"]["message"])

# Not finished yet: long-poll until it is
while request["status"] in ("queued", "running"):
    request = requests.get(API + "/requests/" + request["id"], params={"wait": 20}, headers=headers).json()
if request["status"] != "succeeded":
    raise RuntimeError(request["error"])
print([o["url"] for o in request["outputs"]], request["cost"]["credits"], "API credits", "$" + request["cost"]["usd"])
```

### MCP

The MCP server at `https://api.doitong.com/v1/mcp` exposes the tools `search_models`, `get_model`, `quote`, `run`, `get_request`, `cancel_request`, `list_requests`, `create_upload` and `get_account`. A `run` call for this model:

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "run",
    "arguments": {
      "model_id": "ace-step/audio-outpaint",
      "input": {
        "tags": "lofi, hiphop, drum and bass, trap, chill",
        "audio_url": "https://content.doitong.com/audio/showcase/v3/tools/dub_es.mp3"
      },
      "wait_seconds": 20
    }
  }
}
```

## Response

Every call returns a request object. `status` is one of `queued`, `running`, `succeeded`, `failed`, `canceled`. `outputs` lists the generated files with URLs on our storage (kept forever, or 7 days with `?storage=temporary`; `storage` says which); `output` is the model's own result object with the same URLs.

```json
{
  "id": "req_8k2m4q7x1z9c3v5b6n0p2r4t",
  "object": "request",
  "model": "ace-step/audio-outpaint",
  "status": "succeeded",
  "created_at": "2026-10-20T12:00:00Z",
  "started_at": "2026-10-20T12:00:02Z",
  "completed_at": "2026-10-20T12:00:09Z",
  "queue_position": null,
  "cost": {
    "credits": 6,
    "usd": "0.006",
    "charged": 6,
    "refunded": 0
  },
  "input": {
    "tags": "lofi, hiphop, drum and bass, trap, chill",
    "audio_url": "https://content.doitong.com/audio/showcase/v3/tools/dub_es.mp3"
  },
  "output": {
    "audio": {
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.mp3",
      "content_type": "audio/mpeg",
      "file_name": "0-output.mp3",
      "file_size": 1843200
    },
    "seed": 42,
    "tags": "lofi, hiphop, drum and bass, trap, chill",
    "lyrics": "[inst]"
  },
  "outputs": [
    {
      "type": "audio",
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.mp3",
      "content_type": "audio/mpeg",
      "file_size": 1843200,
      "duration": 12,
      "stored": true
    }
  ],
  "error": null,
  "metrics": {
    "inference_seconds": 6.8
  },
  "urls": {
    "self": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t",
    "cancel": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t/cancel"
  }
}
```

### Output fields (`output`)

| Field | Type | Description |
|---|---|---|
| `audio` | object {url, content_type, file_name, file_size} | 生成された音声ファイル。 |
| `seed` | integer | 生成時に使用したランダムシード。 |
| `tags` | string | 生成時に適用したジャンルタグ。 |
| `lyrics` | string | 生成時に適用した歌詞。 |

## Related models

- [ACE Step](https://doitong.com/developers/models/ace-step.md) (`ace-step`): $0.0002 / second
- [ACE Step Audio Inpaint](https://doitong.com/developers/models/ace-step/audio-inpaint.md) (`ace-step/audio-inpaint`): $0.0002 / second of input audio
- [ACE Step Audio To Audio](https://doitong.com/developers/models/ace-step/audio-to-audio.md) (`ace-step/audio-to-audio`): $0.0002 / second of input audio
- [ACE Step Prompt To Audio](https://doitong.com/developers/models/ace-step/prompt-to-audio.md) (`ace-step/prompt-to-audio`): $0.0002 / second
- [MiniMax Music 3](https://doitong.com/developers/models/minimax/music-3.md) (`minimax/music-3`): $0.002 / second
- [DiffRhythm: Lyrics to Song](https://doitong.com/developers/models/diffrhythm.md) (`diffrhythm`): $0.001 / second
- [Elevenlabs Music](https://doitong.com/developers/models/elevenlabs/music.md) (`elevenlabs/music`): $0.60 / minute of output audio
- [Elevenlabs Music v2](https://doitong.com/developers/models/elevenlabs/music/v2.md) (`elevenlabs/music/v2`): $0.60 / minute of output audio

## Links

- HTML page: https://doitong.com/developers/models/ace-step/audio-outpaint
- All models and guides for AI agents: https://doitong.com/developers/llms.txt
- OpenAPI 3.1 with this model's typed request body: https://doitong.com/developers/openapi.json?model=ace-step/audio-outpaint
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.com/v1/models/ace-step/audio-outpaint