# LTX-2.3 22B · Extend Video API

> プロンプトから既存動画を延長し、音声を生成します。最後の画像も任意で指定できます

`video_url`と`prompt`を受け取り、`num_frames`フレーム（9～481）の続きの映像を生成します。任意の`end_image_url`で延長の終了位置を設定できます。`match_input_fps`でソースのフレームレートを維持し、`generate_audio`で音声を追加します。`video_size`のデフォルトはautoです。出力形式にはmp4、webm、mov、GIFを指定できます。

- Model id: `ltx-2.3-22b/extend-video`
- Made by: Lightricks
- Category: Video to Video
- Output: video
- Price per megapixel of your output video: $0.00161 / megapixel of output video (cheapest run $0.002 (2 API credits))
- Run: `POST https://api.doitong.com/v1/run/ltx-2.3-22b/extend-video`
- Quote: `POST https://api.doitong.com/v1/quote/ltx-2.3-22b/extend-video`
- Docs page: https://doitong.com/ja/developers/models/ltx-2.3-22b/extend-video

## Pricing

Price: **$0.00161 / megapixel of output video**. Price per megapixel of your output video: 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 $0.18 = 180 API credits (112 MP output video × $0.001605).

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/ltx-2.3-22b/extend-video` 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 |
|---|---|---|---|---|---|---|
| `prompt` |  | string | yes |  |  | 動画生成の基礎となるプロンプト。 |
| `video_url` | `video` | string (video URL) | yes |  |  | 延長する動画を指すURL。 |
| `end_image_url` | `end_image` | string (image URL) \| null | no |  |  | 延長動画の終了方法を定義する最終フレーム画像をURLで指定します。 |
| `num_frames` |  | integer | no | `121` | 9 – 481 | 生成する出力のフレーム数。 |
| `video_size` |  | object {width, height} \| enum (string) | no | `auto` | `auto`, `square_hd`, `square`, `portrait_4_3`, `portrait_16_9`, `landscape_4_3`, `landscape_16_9` | 生成された動画のサイズ。 |
| `generate_audio` |  | boolean | no | `true` |  | 動画に生成された音声を含めるかどうかを制御します。 |
| `use_multiscale` |  | boolean | no | `true` |  | 一貫性とディテールを向上させるマルチスケール生成の切り替え。True の場合、小さな予備動画で、要求寸法以上のサイズになる2回目の生成を誘導します。 |
| `match_input_fps` |  | boolean | no | `true` |  | 出力フレームレートの上書き。有効にするとデフォルトの目標FPSをソース動画のFPSに置き換えます。 |
| `fps` |  | number | no | `24` | 1 – 60 | 出力動画のフレームレート。1秒あたりのフレーム数で測定します。 |
| `num_inference_steps` |  | integer | no | `40` | 8 – 50 | 実行された推論ステップ数。 |
| `video_cfg_scale` |  | number | no | `3` | 1 – 20 | 動画のガイダンス設定。値を上げると生成内容の一貫性と焦点が向上します。classifier-free guidance (CFG)を使用します。 |
| `video_stg_scale` |  | number | no | `0` | 0 – 20 | Spatiotemporal Guidance (STG)スケールによる動画の一貫性と焦点の制御。値を上げると両方が強まります。 |
| `video_rescaling_scale` |  | number | no | `0.7` | 0 – 1 | classifier-free guidanceと時空間ガイダンスのバランスを比率で調整する動画の再スケーリング設定。 |
| `video_modality_scale` |  | number | no | `3` | 0 – 10 | 動画と音声の寄与を比率で調整する動画モダリティ設定。 |
| `audio_cfg_scale` |  | number | no | `7` | 1 – 20 | 音声ガイダンス設定。値を上げると生成内容の一貫性と焦点が向上します。classifier-free guidance (CFG)を使用します。 |
| `audio_stg_scale` |  | number | no | `0` | 0 – 20 | Spatiotemporal Guidance (STG)スケールによる音声の一貫性と焦点の制御。値を上げると両方が強まります。 |
| `audio_rescaling_scale` |  | number | no | `0.7` | 0 – 1 | classifier-free guidanceと時空間ガイダンスのバランスを比率で調整する音声の再スケーリング設定。 |
| `audio_modality_scale` |  | number | no | `3` | 0 – 10 | 動画と音声の寄与を比率で調整する音声モダリティ設定。 |
| `gradient_estimation_gamma` |  | number | no | `2` | 0 – 10 | ノイズ除去勾配推定設定。0で推定を無効にし、それ以外では値がgammaを指定します。 |
| `use_restart_sampling` |  | boolean | no | `false` |  | 動画品質向上の可能性がある再起動サンプリングの切り替え。有効にすると各ノイズ除去ステップで少量のノイズを導入します。 |
| `scheduler` |  | enum (string) | no | `ltx2` | `ltx2`, `linear_quadratic`, `beta` | スケジューラーの選択。 |
| `acceleration` |  | enum (string) | no | `regular` | `none`, `regular`, `high`, `full` | 処理に適用する高速化レベル。 |
| `camera_lora` |  | enum (string) | no | `none` | `dolly_in`, `dolly_out`, `dolly_left`, `dolly_right`, `jib_up`, `jib_down`, `static`, `none` | カメラ動作プロンプトだけの場合より正確に生成動画の動きを制御するCamera LoRAの選択。 |
| `camera_lora_scale` |  | number | no | `1` | 0 – 1 | カメラ動作プロンプトだけの場合より正確に生成動画の動きを制御するCamera LoRAの強度。 |
| `negative_prompt` |  | string | no | `news broadcast, 3d animation, computer graphics, pc game, console game, video game, cartoon, childish, watermark, logo, text, on screen text, subtitles, titles, signature, slowmo, static` |  | 動画生成時に使用するネガティブプロンプト。 |
| `seed` |  | integer \| null | no |  |  | 乱数生成を初期化するシード値。 |
| `enable_prompt_expansion` |  | boolean | no | `true` |  | プロンプト拡張を有効にするかどうかを制御します。 |
| `enable_safety_checker` |  | boolean | no | `true` |  | 安全性チェックを有効にするかどうかを制御します。 |
| `video_output_type` |  | enum (string) | no | `X264 (.mp4)` | `X264 (.mp4)`, `VP9 (.webm)`, `PRORES4444 (.mov)`, `GIF (.gif)` | 結果動画の出力タイプ。 |
| `video_quality` |  | enum (string) | no | `high` | `low`, `medium`, `high`, `maximum` | 結果動画の品質レベル。 |
| `video_write_mode` |  | enum (string) | no | `balanced` | `fast`, `balanced`, `small` | 結果動画の書き込みモード。 |
| `distill_lora_first_pass_scale` |  | number | no | `0.2` | 0 – 1 | 初回パスのdistill LoRAスケーリングを制御します。0で無効になります。 |
| `distill_lora_second_pass_scale` |  | number | no | `0.5` | 0 – 1 | 初回以降の各パスにおけるdistill LoRAスケーリングを制御します。 |
| `extend_direction` |  | enum (string) | no | `forward` | `forward`, `backward` | 延長する側。'backward' は冒頭より前に内容を追加し、'forward' は末尾より後に内容を追加します。 |
| `num_context_frames` |  | integer | no | `25` | 0 – 121 | 動画延長時にコンテキストとして使用するフレーム数。 |
| `video_strength` |  | number | no | `1` | 0 – 1 | 動画内容を変更する自由度を制御する条件付け強度。値が小さいほどモデルの裁量が大きくなります。 |
| `audio_strength` |  | number | no | `1` | 0 – 1 | 音声内容を変更する自由度を制御する条件付け強度。値が小さいほどモデルの裁量が大きくなります。 |
| `end_image_strength` |  | number | no | `1` | 0 – 1 | 終了画像が生成動画に与える影響の強さを制御します。 |

File parameters (`video`, `end_image`) 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
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
  "video": "https://content.doitong.com/video/showcase/v3/gen_fox_cartoon.mp4"
}
```

A fuller example:

```json
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
  "video_url": "https://content.doitong.com/video/showcase/v3/gen_fox_cartoon.mp4"
}
```

## 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/ltx-2.3-22b/extend-video?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
    "video_url": "https://content.doitong.com/video/showcase/v3/gen_fox_cartoon.mp4"
  }'

# 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/ltx-2.3-22b/extend-video?wait=20", {
  method: "POST",
  headers,
  body: JSON.stringify({
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
    "video_url": "https://content.doitong.com/video/showcase/v3/gen_fox_cartoon.mp4"
  }),
});
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 = {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
    "video_url": "https://content.doitong.com/video/showcase/v3/gen_fox_cartoon.mp4",
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/ltx-2.3-22b/extend-video", 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": "ltx-2.3-22b/extend-video",
      "input": {
        "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
        "video_url": "https://content.doitong.com/video/showcase/v3/gen_fox_cartoon.mp4"
      },
      "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": "ltx-2.3-22b/extend-video",
  "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": 180,
    "usd": "0.18",
    "charged": 180,
    "refunded": 0
  },
  "input": {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
    "video_url": "https://content.doitong.com/video/showcase/v3/gen_fox_cartoon.mp4"
  },
  "output": {
    "video": {
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.mp4",
      "content_type": "video/mp4",
      "file_name": "0-output.mp4",
      "file_size": 1843200,
      "width": 1024,
      "height": 768,
      "fps": 1.0,
      "duration": 5,
      "num_frames": 1
    },
    "seed": 42,
    "prompt": "A woman stands still amid a busy neon-lit street at night. The camera slowly dollies in toward her face as people blur past, their motion emphasizing her calm presence. City lights flicker and reflections shift across her denim jacket."
  },
  "outputs": [
    {
      "type": "video",
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.mp4",
      "content_type": "video/mp4",
      "file_size": 1843200,
      "width": 1280,
      "height": 720,
      "duration": 5,
      "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 |
|---|---|---|
| `video` | object {url, content_type, file_name, file_size, width, height, fps, duration, num_frames} | モデルが生成した動画。 |
| `seed` | integer | 乱数生成の初期化に使用するシード値。 |
| `prompt` | string | 生成を誘導するプロンプト。 |

## Related models

- [LTX-2.3 22B · Text to Video](https://doitong.com/developers/models/ltx-2.3-22b/text-to-video.md) (`ltx-2.3-22b/text-to-video`): $0.00161 / megapixel of output video
- [LTX-2.3 22B · Text to Video · LoRA](https://doitong.com/developers/models/ltx-2.3-22b/text-to-video/lora.md) (`ltx-2.3-22b/text-to-video/lora`): $0.00181 / megapixel of output video
- [LTX-2.3 22B · Image to Video](https://doitong.com/developers/models/ltx-2.3-22b/image-to-video.md) (`ltx-2.3-22b/image-to-video`): $0.00161 / megapixel of output video
- [LTX-2.3 22B · Image to Video · LoRA](https://doitong.com/developers/models/ltx-2.3-22b/image-to-video/lora.md) (`ltx-2.3-22b/image-to-video/lora`): $0.00181 / megapixel of output video
- [LTX 2.3 22B](https://doitong.com/developers/models/ltx-2.3-22b/reference-video-to-video/lora.md) (`ltx-2.3-22b/reference-video-to-video/lora`): $0.00181 / megapixel of output video
- [LTX-2.3 22B · Extend Video · LoRA](https://doitong.com/developers/models/ltx-2.3-22b/extend-video/lora.md) (`ltx-2.3-22b/extend-video/lora`): $0.00181 / megapixel of output video
- [LTX-2.3 22B · Reference Video to Video](https://doitong.com/developers/models/ltx-2.3-22b/reference-video-to-video.md) (`ltx-2.3-22b/reference-video-to-video`): $0.00161 / megapixel of output video
- [LTX-2.3 22B · Video to Video](https://doitong.com/developers/models/ltx-2.3-22b/video-to-video.md) (`ltx-2.3-22b/video-to-video`): $0.00161 / megapixel of output video

## Links

- HTML page: https://doitong.com/developers/models/ltx-2.3-22b/extend-video
- 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=ltx-2.3-22b/extend-video
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.com/v1/models/ltx-2.3-22b/extend-video