# Ltx 2.3 Quality · Extend Video API

> Setzt e Video no vir oder no hannen fort, mat engem optionalen Bild als Schluss-Keyframe

Verlängert en existente Clip, andeems neit Videomaterial generéiert gëtt, geleet vun engem obligatoresche `prompt`. `extend_direction` ass `forward`, fir vum Enn un weiderzefueren, oder `backward`, fir en neien Ufank ze erstellen. `num_context_frames` (9 to 121) leet fest, wéi vill vum Quellmaterial iwwerlappt, an `num_frames` (9 to 481) bestëmmt d'Längt vum Segment. En optionalen `end_image_url` fixéiert den definitive Schlësselframe, an `match_input_fps` behält d'Bildrate vun der Quell.

- Model id: `ltx-2.3-quality/extend-video`
- Made by: Lightricks
- Category: Video to Video
- Output: video
- Price per megapixel of your output video: $0.00241 / megapixel of output video (cheapest run $0.003 (3 API credits))
- Run: `POST https://api.doitong.com/v1/run/ltx-2.3-quality/extend-video`
- Quote: `POST https://api.doitong.com/v1/quote/ltx-2.3-quality/extend-video`
- Docs page: https://doitong.com/lb/developers/models/ltx-2.3-quality/extend-video

## Pricing

Price: **$0.00241 / 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 $0.27 = 270 API credits (112 MP output video × $0.002408).

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-quality/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 |  |  | Prompt, deen déi gewënschten Fortsetzung vum Video spezifizéiert. |
| `video_url` | `video` | string (video URL) | yes |  |  | URL vum Video, deen verlängert gëtt. |
| `extend_direction` |  | enum (string) | no | `forward` | `forward`, `backward` | Video-Verlängerungsmodus: 'backward' erstellt en neien Ufank, wärend 'forward' de Video iwwer säin Enn eraus weiderféiert. |
| `num_frames` |  | integer | no | `121` | 9 – 481 | Frame-Zuel fir de Kontext bei der Videoverlängerung, ënner engem Stable-Generatiounsbudget fir Opléisung multiplizéiert mat Frames: bei 24 fps ongeféier 20 Sekonne fir 480p-Klass, 11 Sekonne fir 720p-Klass oder 5 Sekonne fir 1080p-Klass. Ufroen iwwer de Budget ginn 422 zeréck; reduzéiert `num_frames` oder wielt eng méi kleng Opléisung. D'Zuel enthält `num_context_frames`, déi mam Quellvideo iwwerlappen; déi bäigefüügt Dauer ass ongeféier (`num_frames` - `num_context_frames`) / `frames_per_second` Sekonnen. |
| `num_context_frames` |  | integer | no | `25` | 9 – 121 | Ugefrote Quell-Frame-Zuel fir Verlängerungskontext/-Iwwerlappung, limitéiert duerch d'Zuel vun de Frames an der Quell. D'Zuel gëtt ofgerënnt, fir an d'LTX-Gitter vun 8k+1 ze passen. |
| `end_image_url` | `end_image` | string (image URL) \| null | no |  |  | Optional Keyframe-Bild, dat den neie éischte Frame bei enger Verlängerung no hannen oder den neie leschte Frame bei enger Verlängerung no vir festleet. |
| `end_image_strength` |  | number | no | `1` | 0 – 1 | Optional Conditioning-Stäerkt vum Schluss-Keyframe: eng Reduktioun gëtt dem Modell méi Fräiheet, wärend 1.0 eng exakt Iwwerstëmmung erzwéngt. |
| `resolution` |  | object {width, height} \| enum (string) | no | `auto` | `auto`, `square_hd`, `square`, `portrait_4_3`, `portrait_16_9`, `landscape_4_3`, `landscape_16_9` | Dimensioune vum generéierte Video, op Inkrementer vun 32px ausgeriicht — zum Beispill gëtt 1920x1080 zu 1888x1056 — an d'Quell gëtt fir den zesummegesate Output op dës Dimensioune skaléiert. Stable Verlängerunge kënne bei méi niddreger Opléisung méi laang a bei méi héijer méi kuerz sinn. 'auto' behält d'Quell-Dimensiounen an d'Bildformat sou wäit wéi d'LTX-Limiten et erlaben. |
| `match_input_fps` |  | boolean | no | `true` |  | Output-Frame-Rate, déi bei Aktivéierung un d'Quell ugepasst gëtt an `frames_per_second` iwwerschreift. De Quell-FPS gëtt op eng ganz Zuel geronnt an op de ënnerstëtzte Beräich limitéiert. |
| `frames_per_second` |  | number | no | `24` | 1 – 60 | Output-Video-Frame-Rate, gemooss a Frames pro Sekonn. |
| `video_strength` |  | number | no | `1` | 0 – 1 | Conditioning-Stäerkt vum Quellkontext: eng Reduktioun erlaabt dem Modell méi Fräiheet. Bei 1.0 bleiwen déi iwwerlappend Frames un d'Quell gebonnen, wat den Iwwergang nahtlos mécht. |
| `num_inference_steps` |  | integer | no | `15` | 8 – 30 | Setzt d'Zuel vun den Inference-Schrëtt op bis zu 30; wann onverännert, ginn 15 benotzt. |
| `guidance_scale` |  | number | no | `1` | 1 – 20 | Passt classifier-free guidance mat dëser Skala un; de Standard ass op héich Qualitéit a séier Generatioun ofgestëmmt. |
| `generate_audio` |  | boolean | no | `true` |  | Audio-Toggle fir d'Verlängerung: ausgeschalt léisst dat bäigefüügt Segment stëll a behält d'Audiospur vum Quellvideo. Ageschalt generéiert Audio fir d'Verlängerung a mëscht en um Iwwergang mat der Quell. |
| `negative_prompt` |  | string | no | `color distortion, overexposure, static, blurry details, subtitles, style, artwork, painting, frame, still, dim overall tone, worst quality, low quality, JPEG compression artifacts, ugly, mutilated, extra fingers, poorly drawn hands, poorly drawn face, deformed, disfigured, malformed limbs, fused fingers, motionless frame, cluttered background, three legs, crowded background, walking backwards` |  | Negativen Prompt, deen ugëtt, wat d'Generatioun vermeide soll. |
| `seed` |  | integer \| null | no |  |  | Seed, deen d'Generatioun reproduzéierbar mécht. Wann et op None gesat gëtt, gëtt e Seed zoufälleg gewielt. |
| `enable_prompt_expansion` |  | boolean | no | `true` |  | Steiert, ob d'Prompt-Erweiderung aktivéiert ass. |
| `enable_safety_checker` |  | boolean | no | `true` |  | Steiert, ob d'Sécherheetskontroll aktivéiert ass. |
| `video_quality` |  | enum (string) | no | `high` | `low`, `medium`, `high`, `maximum` | Qualitéitsvirstellung, déi op den Output-Video applizéiert gëtt. |
| `video_write_mode` |  | enum (string) | no | `balanced` | `fast`, `balanced`, `small` | Schreifmodus vum resultéierende Video. |

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-quality/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-quality/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-quality/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-quality/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-quality/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": 270,
    "usd": "0.27",
    "charged": 270,
    "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
    },
    "seed": 42,
    "prompt": "string"
  },
  "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} | Video, dee vum Modell produzéiert gëtt. |
| `seed` | integer | Tatsächlech Seed, deen wärend der Generatioun applizéiert gëtt. |
| `prompt` | string | Generatiouns-Prompt, inklusiv all Erweiderung, déi virun der Benotzung applizéiert gouf. |

## Related models

- [Ltx 2.3 Quality · Text to Video](https://doitong.com/developers/models/ltx-2.3-quality/text-to-video.md) (`ltx-2.3-quality/text-to-video`): $0.00241 / megapixel of output video
- [Ltx 2.3 Quality · Text to Video · LoRA](https://doitong.com/developers/models/ltx-2.3-quality/text-to-video/lora.md) (`ltx-2.3-quality/text-to-video/lora`): $0.00271 / megapixel of output video
- [Ltx 2.3 Quality · Image to Video](https://doitong.com/developers/models/ltx-2.3-quality/image-to-video.md) (`ltx-2.3-quality/image-to-video`): $0.00241 / megapixel of output video
- [Ltx 2.3 Quality · Image to Video · LoRA](https://doitong.com/developers/models/ltx-2.3-quality/image-to-video/lora.md) (`ltx-2.3-quality/image-to-video/lora`): $0.00271 / megapixel of output video
- [Ltx 2.3 Quality · Ingredient](https://doitong.com/developers/models/ltx-2.3-quality/ingredient.md) (`ltx-2.3-quality/ingredient`): $0.00241 / megapixel of output video
- [Ltx 2.3 Quality · Clean Plate](https://doitong.com/developers/models/ltx-2.3-quality/clean-plate.md) (`ltx-2.3-quality/clean-plate`): $0.00241 / megapixel of output video
- [Ltx 2.3 Quality · Colorization](https://doitong.com/developers/models/ltx-2.3-quality/colorization.md) (`ltx-2.3-quality/colorization`): $0.00241 / megapixel of output video
- [Ltx 2.3 Quality · Cross Eyed](https://doitong.com/developers/models/ltx-2.3-quality/cross-eyed.md) (`ltx-2.3-quality/cross-eyed`): $0.00241 / megapixel of output video

## Links

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