# Kling 4.0 Reference to Video API

> Genera video di 3-30 secondi che mantengono l'aspetto di un massimo di 10 immagini di riferimento, 5 video di riferimento e 7 elementi

Crea video da un `prompt` testuale oltre a immagini di riferimento, video di riferimento ed elementi di personaggi o oggetti, citati nel prompt come @Image1, @Video1 o @Element1. La durata va da 3 a 30 secondi (predefinita: 5), con output a 720p o 1080p e rapporti d'aspetto auto, 16:9, 9:16, 1:1 o 21:9. Usa `multi_prompt` per prompt specifici per ogni inquadratura; in questo caso, la durata totale è la somma delle durate delle inquadrature. I limiti sono 10 immagini, 5 video da 3-30s ciascuno e 7 elementi, di cui un massimo di 3 può includere una voce.

- Model id: `kling/v4/reference-to-video`
- Made by: Kling
- Category: Reference to Video
- Output: video
- Price per second of your output video: from $0.157 / second of output video (cheapest run $0.157 (157 API credits))
- Run: `POST https://api.doitong.com/v1/run/kling/v4/reference-to-video`
- Quote: `POST https://api.doitong.com/v1/quote/kling/v4/reference-to-video`
- Docs page: https://doitong.com/it/developers/models/kling/v4/reference-to-video

## Pricing

Price: **from $0.157 / second of output video** (the lowest tier; the quote prices your exact input). Price per second 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.

Price by tier:

- 720p: $0.157 / second of output video
- 1080p: $0.235 / second of output video

The full example input below costs $1.175 = 1175 API credits (5 s output video × $0.235 (1080p)).

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/kling/v4/reference-to-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 \| null | no |  | ≤ 2500 characters | Istruzioni di generazione che soddisfano il requisito di fornire `prompt` o `multi_prompt`. Per fare riferimento agli input forniti, usa @Image1, @Video1, @Element1 e così via. |
| `multi_prompt` |  | array of object {prompt, duration} \| null | no |  | ≥ 1 items | Istruzioni di generazione inquadratura per inquadratura, con ogni prompt che definisce un'inquadratura la cui durata contribuisce alla durata complessiva del video. |
| `multi_prompt[].prompt` |  | string | yes |  | 1 – 512 characters | Istruzioni testuali per l'inquadratura corrente. |
| `multi_prompt[].duration` |  | integer | no | `5` | 1 – 30 | Durata di una singola inquadratura, misurata in secondi. |
| `duration` |  | integer | no | `5` | 3 – 30 | Durata del video in secondi, da 3 a 30. |
| `start_image_url` | `image` | string (image URL) \| null | no |  |  | Immagine facoltativa del primo fotogramma che conta ai fini del limite delle immagini di riferimento. La dimensione massima del file è 30.0 MB; larghezza e altezza devono raggiungere almeno 300 px ciascuna, con un rapporto d'aspetto compreso tra 0.40 e 2.50. |
| `image_urls` | `images` | array of image URL \| null | no |  | ≤ 10 items | Immagini di riferimento richiamate tramite @Image1, @Image2 e così via, con un massimo di 10 immagini. Ogni file è limitato a 30.0 MB, richiede almeno 300 px in entrambe le dimensioni e deve avere un rapporto d'aspetto compreso tra 0.40 e 2.50. |
| `video_urls` | `videos` | array of video URL \| null | no |  | ≤ 5 items | Fino a 5 video di riferimento, richiamati tramite @Video1, @Video2 e così via; ciascuno dura 3–30 secondi (al massimo 30.05 secondi) e la loro durata totale insieme ai video degli elementi non può superare 30 secondi. Ogni file non deve superare 300 MB, con larghezza e altezza comprese tra 700 px e 4553 px. Il rapporto d'aspetto deve essere compreso tra 0.40 e 2.50 e la frequenza fotogrammi tra 23.9 e 60.05 FPS. |
| `elements` |  | array of object {frontal_image_url, reference_image_urls, video_url, voice_id} \| null | no |  | ≤ 7 items | Raccolta di fino a 7 personaggi o oggetti, di cui al massimo 3 possono includere un `voice_id` e al massimo 3 possono usare un video. Richiama questi elementi come @Element1, @Element2 e così via. |
| `elements[].frontal_image_url` |  | string (image URL) \| null | no |  |  | Immagine frontale che mostra la vista principale dell'elemento. La dimensione massima del file è 30.0 MB; entrambe le dimensioni devono essere di almeno 300 px e il rapporto d'aspetto deve essere compreso tra 0.40 e 2.50. |
| `elements[].reference_image_urls` |  | array of image URL \| null | no |  | ≤ 3 items | Immagini supplementari che mostrano diverse angolazioni dell'elemento, con da 1 a 3 viste. Ogni file può avere una dimensione massima di 30.0 MB, deve misurare almeno 300 px in entrambe le dimensioni e deve avere un rapporto d'aspetto compreso tra 0.40 e 2.50. |
| `elements[].video_url` |  | string (video URL) \| null | no |  |  | Rappresentazione video di un elemento al posto delle immagini, della durata di 3–30 secondi (al massimo 30.05 secondi). Il file non deve superare 300 MB; larghezza e altezza devono essere comprese tra 700–4553 px. I rapporti d'aspetto supportati vanno da 0.40 a 2.50, con frequenze fotogrammi di 23.9–60.05 FPS. |
| `elements[].voice_id` |  | string \| null | no |  |  | Voce assegnata all'elemento. |
| `resolution` |  | enum (string) | no | `1080p` | `720p`, `1080p` | Risoluzione dell'output. |
| `aspect_ratio` |  | enum (string) | no | `16:9` | `auto`, `16:9`, `9:16`, `1:1`, `21:9` | Proporzioni del video, selezionate esplicitamente o derivate dai riferimenti scegliendo 'auto'. |

File parameters (`image`, `images`, `videos`) 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
{}
```

A fuller example:

```json
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
}
```

## 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/kling/v4/reference-to-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"
  }'

# 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/kling/v4/reference-to-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"
  }),
});
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",
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/kling/v4/reference-to-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": "kling/v4/reference-to-video",
      "input": {
        "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
      },
      "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": "kling/v4/reference-to-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": 1175,
    "usd": "1.175",
    "charged": 1175,
    "refunded": 0
  },
  "input": {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
  },
  "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
    }
  },
  "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. |

## Related models

- [Kling 4.0 Text to Video](https://doitong.com/developers/models/kling/v4/text-to-video.md) (`kling/v4/text-to-video`): from $0.157 / second of output video
- [Seedance 2.0 Fast Reference to Video](https://doitong.com/developers/models/bytedance/seedance-2.0/fast/reference-to-video.md) (`bytedance/seedance-2.0/fast/reference-to-video`): from $0.113 / second
- [Seedance 2.0 Reference to Video](https://doitong.com/developers/models/bytedance/seedance-2.0/reference-to-video.md) (`bytedance/seedance-2.0/reference-to-video`): from $0.141 / second
- [Wan 3.0 Reference to Video](https://doitong.com/developers/models/alibaba/wan-3.0/reference-to-video.md) (`alibaba/wan-3.0/reference-to-video`): from $0.05 / second
- [Kling O1 Reference Image to Video \[Pro\]](https://doitong.com/developers/models/kling-video/o1/reference-to-video.md) (`kling-video/o1/reference-to-video`): $0.112 / second
- [Kling O1 Reference Image to Video \[Standard\]](https://doitong.com/developers/models/kling-video/o1/standard/reference-to-video.md) (`kling-video/o1/standard/reference-to-video`): $0.084 / second
- [Kling O3 Reference to Video \[Pro\]](https://doitong.com/developers/models/kling-video/o3/pro/reference-to-video.md) (`kling-video/o3/pro/reference-to-video`): from $0.112 / second
- [Kling O3 Reference to Video \[Standard\]](https://doitong.com/developers/models/kling-video/o3/standard/reference-to-video.md) (`kling-video/o3/standard/reference-to-video`): from $0.084 / second

## Links

- HTML page: https://doitong.com/developers/models/kling/v4/reference-to-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=kling/v4/reference-to-video
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.com/v1/models/kling/v4/reference-to-video