# Ltx 2.3 Quality · Extend Video API

> Prosegue un video in avanti o all'indietro, con immagine facoltativa del fotogramma chiave finale

Estende un clip esistente generando nuove riprese guidate da un `prompt` obbligatorio. `extend_direction` è `forward` per continuare dalla fine o `backward` per creare un nuovo inizio. `num_context_frames` (9 to 121) imposta la quantità di sovrapposizione con la sorgente, mentre `num_frames` (9 to 481) imposta la durata del segmento. Un `end_image_url` facoltativo fissa il fotogramma chiave finale e `match_input_fps` mantiene la frequenza dei fotogrammi della sorgente.

- 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/it/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 che specifica la continuazione desiderata del video. |
| `video_url` | `video` | string (video URL) | yes |  |  | URL che punta al video da estendere. |
| `extend_direction` |  | enum (string) | no | `forward` | `forward`, `backward` | Modalità di estensione del video: 'backward' crea un nuovo inizio, mentre 'forward' continua il video oltre la fine. |
| `num_frames` |  | integer | no | `121` | 9 – 481 | Numero di fotogrammi dell'estensione, soggetto a un budget di generazione stabile sul prodotto tra risoluzione e fotogrammi: a 24 fps, circa 20 secondi per la classe 480p, 11 secondi per la classe 720p o 5 secondi per la classe 1080p. Le richieste che superano il budget restituiscono 422; riduci `num_frames` o scegli una risoluzione inferiore. Il numero include `num_context_frames` sovrapposti alla sorgente, quindi la durata aggiunta è circa (`num_frames` - `num_context_frames`) / `frames_per_second` secondi. |
| `num_context_frames` |  | integer | no | `25` | 9 – 121 | Numero di fotogrammi sorgente richiesto per il contesto o la sovrapposizione dell'estensione, limitato dal numero di fotogrammi contenuti nella sorgente. Il numero viene arrotondato per difetto per adattarsi alla griglia LTX di 8k+1. |
| `end_image_url` | `end_image` | string (image URL) \| null | no |  |  | Immagine keyframe opzionale che imposta il nuovo primo fotogramma dell'estensione quando si estende all'indietro oppure l'ultimo fotogramma quando si estende in avanti. |
| `end_image_strength` |  | number | no | `1` | 0 – 1 | Intensità opzionale del condizionamento del keyframe finale: ridurla consente al modello maggiore libertà, mentre 1.0 impone una corrispondenza esatta. |
| `resolution` |  | object {width, height} \| enum (string) | no | `auto` | `auto`, `square_hd`, `square`, `portrait_4_3`, `portrait_16_9`, `landscape_4_3`, `landscape_16_9` | Dimensioni del video generato, allineate a incrementi di 32px — ad esempio, 1920x1080 diventa 1888x1056 — con la sorgente ridimensionata a queste dimensioni per l'output con concatenazione. Le estensioni stabili possono essere più lunghe a risoluzioni inferiori e più brevi a risoluzioni superiori. Scegliendo 'auto' si mantengono, nei limiti di LTX, le dimensioni e il rapporto d'aspetto della sorgente. |
| `match_input_fps` |  | boolean | no | `true` |  | Quando abilitato, adatta il fotogramma rate di output alla sorgente, sostituendo `frames_per_second`. L'FPS della sorgente viene arrotondato a un intero e limitato all'intervallo supportato. |
| `frames_per_second` |  | number | no | `24` | 1 – 60 | Fotogramma rate del video di output, misurato in fotogrammi al secondo. |
| `video_strength` |  | number | no | `1` | 0 – 1 | Intensità del condizionamento del contesto sorgente: ridurla consente maggiore libertà al modello. A 1.0, i fotogrammi sovrapposti restano vincolati alla sorgente, rendendo fluida la transizione. |
| `num_inference_steps` |  | integer | no | `15` | 8 – 30 | Imposta quanti passaggi di inferenza eseguire, fino a 30; se lasciato invariato, usa 15. |
| `guidance_scale` |  | number | no | `1` | 1 – 20 | Regola la guidance classifier-free usando questa scala; la sua regolazione predefinita mira a un'elevata qualità e a una generazione rapida. |
| `generate_audio` |  | boolean | no | `true` |  | Interruttore dell'audio dell'estensione: disattivato lascia silenzioso il segmento aggiunto mantenendo la traccia audio del video sorgente. Attivato genera l'audio dell'estensione e lo fonde con quello sorgente nel punto di giunzione. |
| `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` |  | Prompt negativo che specifica cosa la generazione deve evitare. |
| `seed` |  | integer \| null | no |  |  | Seed che rende riproducibile la generazione. Impostarlo su None seleziona casualmente un seed. |
| `enable_prompt_expansion` |  | boolean | no | `true` |  | Controlla se l'espansione del prompt è abilitata. |
| `enable_safety_checker` |  | boolean | no | `true` |  | Controlla se il controllo di sicurezza è abilitato. |
| `video_quality` |  | enum (string) | no | `high` | `low`, `medium`, `high`, `maximum` | Preset di qualità applicato al video di output. |
| `video_write_mode` |  | enum (string) | no | `balanced` | `fast`, `balanced`, `small` | Modalità di scrittura del video risultante. |

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 prodotto dal modello. |
| `seed` | integer | Seed effettivamente applicato durante la generazione. |
| `prompt` | string | Prompt di generazione, inclusa qualsiasi espansione applicata prima dell'uso. |

## 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