# Ltx 2.3 Quality · Extend Video API

> Nastavlja video unaprijed ili unatrag, uz neobaveznu sliku završnog ključnog kadra

Produljuje postojeći isječak generiranjem novih snimki vođenih obaveznim parametrom `prompt`. `extend_direction` je `forward` za nastavak od kraja ili `backward` za stvaranje novog početka. `num_context_frames` (9 to 121) određuje koliko se izvorni sadržaj preklapa, a `num_frames` (9 to 481) određuje duljinu segmenta. Neobavezni `end_image_url` fiksira završni ključni kadar, a `match_input_fps` zadržava broj sličica izvora.

- 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/hr/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 koji određuje željeni nastavak videa. |
| `video_url` | `video` | string (video URL) | yes |  |  | URL videa koji će se produljiti. |
| `extend_direction` |  | enum (string) | no | `forward` | `forward`, `backward` | Način produljenja videa: 'backward' stvara novi početak, a 'forward' nastavlja video nakon njegova završetka. |
| `num_frames` |  | integer | no | `121` | 9 – 481 | Broj sličica za produljenje, podložan proračunu stabilnog generiranja za razlučivost pomnoženu brojem sličica: pri 24 fps približno 20 sekundi za razred 480p, 11 sekundi za razred 720p ili 5 sekundi za razred 1080p. Zahtjevi koji premašuju proračun vraćaju 422; smanjite `num_frames` ili odaberite manju razlučivost. Broj uključuje `num_context_frames` koje se preklapaju s izvorom, pa je dodano trajanje približno (`num_frames` - `num_context_frames`) / `frames_per_second` sekundi. |
| `num_context_frames` |  | integer | no | `25` | 9 – 121 | Broj izvornih sličica zatražen za kontekst/preklapanje produljenja, ograničen brojem sličica koje izvor sadrži. Broj se zaokružuje naniže kako bi odgovarao LTX mreži od 8k+1. |
| `end_image_url` | `end_image` | string (image URL) \| null | no |  |  | Neobavezna slika ključne sličice koja postavlja novi prvi kadar produljenja pri produljenju unatrag ili njegov zadnji kadar pri produljenju unaprijed. |
| `end_image_strength` |  | number | no | `1` | 0 – 1 | Neobavezna jačina kondicioniranja završne ključne sličice: smanjenje daje modelu veću slobodu, dok 1.0 nameće točno podudaranje. |
| `resolution` |  | object {width, height} \| enum (string) | no | `auto` | `auto`, `square_hd`, `square`, `portrait_4_3`, `portrait_16_9`, `landscape_4_3`, `landscape_16_9` | Dimenzije generiranog videa, poravnate na korake od 32px — primjerice, 1920x1080 postaje 1888x1056 — pri čemu se izvor mijenja na te dimenzije za spojeni izlaz. Stabilna produljenja mogu biti dulja pri manjim razlučivostima i kraća pri većima. Odabirom 'auto' zadržavaju se dimenzije i omjer stranica izvora u granicama LTX-a. |
| `match_input_fps` |  | boolean | no | `true` |  | Usklađivanje izlazne brzine izmjene sličica s izvorom kada je omogućeno, čime se nadjačava `frames_per_second`. FPS izvora zaokružuje se na cijeli broj i ograničava na podržani raspon. |
| `frames_per_second` |  | number | no | `24` | 1 – 60 | Brzina izmjene sličica izlaznog videa, mjerena u sličicama u sekundi. |
| `video_strength` |  | number | no | `1` | 0 – 1 | Jačina kondicioniranja konteksta izvora: smanjenje dopušta veću slobodu modela. Pri 1.0 preklapajuće sličice ostaju zaključane na izvor, čime prijelaz postaje neprimjetan. |
| `num_inference_steps` |  | integer | no | `15` | 8 – 30 | Postavite broj koraka zaključivanja, najviše 30; nepromijenjena vrijednost koristi 15. |
| `guidance_scale` |  | number | no | `1` | 1 – 20 | Prilagodite usmjeravanje bez klasifikatora ovom skalom; zadano podešavanje cilja visoku kvalitetu i brzo generiranje. |
| `generate_audio` |  | boolean | no | `true` |  | Prekidač zvuka produljenja: isključeno ostavlja dodani segment bez zvuka, uz zadržavanje zvučnog zapisa izvornog videa. Uključeno generira audio za produljenje i križno ga pretapa s izvorom na spoju. |
| `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` |  | Negativni prompt koji navodi što generiranje treba izbjegavati. |
| `seed` |  | integer \| null | no |  |  | Seed koji omogućuje ponovljivo generiranje. Postavljanjem na None seed se odabire nasumično. |
| `enable_prompt_expansion` |  | boolean | no | `true` |  | Određuje je li proširivanje prompta omogućeno. |
| `enable_safety_checker` |  | boolean | no | `true` |  | Kontrolira je li provjera sigurnosti omogućena. |
| `video_quality` |  | enum (string) | no | `high` | `low`, `medium`, `high`, `maximum` | Unaprijed postavljena kvaliteta koja se primjenjuje na izlazni video. |
| `video_write_mode` |  | enum (string) | no | `balanced` | `fast`, `balanced`, `small` | Način zapisivanja rezultirajućeg videozapisa. |

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} | Videozapis koji je izradio model. |
| `seed` | integer | Stvarno sjeme primijenjeno tijekom generiranja. |
| `prompt` | string | Prompt za generiranje, uključujući svako proširenje primijenjeno prije upotrebe. |

## 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