# Ltx 2.3 Quality · Extend Video API

> Zet een video vooruit of achteruit voort, met een optionele afbeelding voor het laatste keyframe

Verlengt een bestaande clip door nieuwe beelden te genereren op basis van een verplichte `prompt`. `extend_direction` is `forward` om vanaf het einde door te gaan of `backward` om een nieuw begin te maken. `num_context_frames` (9 to 121) bepaalt hoeveel van de bron overlapt en `num_frames` (9 to 481) bepaalt de segmentlengte. Een optionele `end_image_url` legt het laatste keyframe vast en `match_input_fps` behoudt de framerate van de bron.

- 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/nl/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 die de gewenste voortzetting van de video specificeert. |
| `video_url` | `video` | string (video URL) | yes |  |  | URL die verwijst naar de video die wordt verlengd. |
| `extend_direction` |  | enum (string) | no | `forward` | `forward`, `backward` | Modus voor videoverlenging: 'backward' maakt een nieuw begin, terwijl 'forward' de video na het einde voortzet. |
| `num_frames` |  | integer | no | `121` | 9 – 481 | Aantal verlengingsframes, onderhevig aan een budget voor stabiele generatie op basis van resolutie vermenigvuldigd met frames: bij 24 fps ongeveer 20 seconden voor 480p-klasse, 11 seconden voor 720p-klasse of 5 seconden voor 1080p-klasse. Requests die het budget overschrijden geven 422; verlaag `num_frames` of kies een lagere resolutie. Het aantal omvat `num_context_frames` die de bron overlappen, dus de toegevoegde duur is ongeveer (`num_frames` - `num_context_frames`) / `frames_per_second` seconden. |
| `num_context_frames` |  | integer | no | `25` | 9 – 121 | Gevraagd aantal bronframes voor verlengingscontext/overlap, beperkt door het aantal frames in de bron. Het aantal wordt naar beneden afgerond zodat het in het LTX-raster van 8k+1 past. |
| `end_image_url` | `end_image` | string (image URL) \| null | no |  |  | Optionele keyframeafbeelding die het nieuwe eerste frame van de verlenging instelt bij achterwaarts verlengen, of het laatste frame bij voorwaarts verlengen. |
| `end_image_strength` |  | number | no | `1` | 0 – 1 | Optionele conditioneringssterkte voor het eind-keyframe: verlagen geeft het model meer vrijheid, terwijl 1.0 een exacte overeenkomst afdwingt. |
| `resolution` |  | object {width, height} \| enum (string) | no | `auto` | `auto`, `square_hd`, `square`, `portrait_4_3`, `portrait_16_9`, `landscape_4_3`, `landscape_16_9` | Afmetingen van de gegenereerde video, afgestemd op stappen van 32px — zo wordt 1920x1080 bijvoorbeeld 1888x1056 — waarbij de bron voor de samengevoegde uitvoer naar deze afmetingen wordt geschaald. Stabiele verlengingen kunnen bij lagere resoluties langer en bij hogere resoluties korter zijn. Met 'auto' blijven de bronafmetingen en beeldverhouding behouden voor zover de LTX-limieten dit toestaan. |
| `match_input_fps` |  | boolean | no | `true` |  | Aanpassing van de uitvoerframesnelheid aan de bron wanneer dit is ingeschakeld, waarbij `frames_per_second` wordt overschreven. De FPS van de bron wordt afgerond op een geheel getal en beperkt tot het ondersteunde bereik. |
| `frames_per_second` |  | number | no | `24` | 1 – 60 | Framesnelheid van de uitvoervideo, gemeten in frames per seconde. |
| `video_strength` |  | number | no | `1` | 0 – 1 | Conditioneringssterkte voor de broncontext: verlagen geeft het model meer vrijheid. Bij 1.0 blijven de overlappende frames aan de bron vergrendeld, waardoor de overgang naadloos verloopt. |
| `num_inference_steps` |  | integer | no | `15` | 8 – 30 | Stel het aantal inference-stappen in, maximaal 30; ongewijzigd gebruikt dit 15. |
| `guidance_scale` |  | number | no | `1` | 1 – 20 | Pas classifier-free guidance aan met deze schaal; de standaardafstelling is gericht op zowel hoge kwaliteit als snelle generatie. |
| `generate_audio` |  | boolean | no | `true` |  | Schakelaar voor audio bij verlenging: uit laat het toegevoegde segment stil en behoudt de audiotrack van de bronvideo. Aan genereert audio voor de verlenging en maakt bij de overgang een crossfade met de bron. |
| `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` |  | Negatieve prompt die specificeert wat de generatie moet vermijden. |
| `seed` |  | integer \| null | no |  |  | Seed die generatie reproduceerbaar maakt. Als je deze instelt op None, wordt willekeurig een seed gekozen. |
| `enable_prompt_expansion` |  | boolean | no | `true` |  | Bepaalt of promptuitbreiding is ingeschakeld. |
| `enable_safety_checker` |  | boolean | no | `true` |  | Bepaalt of veiligheidscontrole is ingeschakeld. |
| `video_quality` |  | enum (string) | no | `high` | `low`, `medium`, `high`, `maximum` | Kwaliteitsvoorinstelling die op de uitvoervideo wordt toegepast. |
| `video_write_mode` |  | enum (string) | no | `balanced` | `fast`, `balanced`, `small` | Schrijfmodus van de resulterende 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 die door het model is geproduceerd. |
| `seed` | integer | Werkelijke seed die tijdens de generatie wordt toegepast. |
| `prompt` | string | Generatieprompt, inclusief eventuele uitbreiding die vóór gebruik is toegepast. |

## 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