# Kling 4.0 Reference to Video API

> Genererer 3-30 sekunders videoer, der bevarer udseendet af op til 10 referencebilleder, 5 referencevideoer og 7 elementer

Opretter video ud fra en tekstbaseret `prompt` samt referencebilleder, referencevideoer og karakter- eller objektelementer, som refereres i prompten som @Image1, @Video1 eller @Element1. Varigheden går fra 3 til 30 sekunder (standard 5), med output i 720p eller 1080p og billedformaterne auto, 16:9, 9:16, 1:1 eller 21:9. Brug `multi_prompt` til prompts pr. sekvens; i så fald er den samlede længde summen af sekvensernes varigheder. Grænserne er 10 billeder, 5 videoer på hver 3-30s og 7 elementer, hvoraf op til 3 kan have en stemme.

- 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/da/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 | Genereringsinstruktioner, der opfylder kravet om at angive enten `prompt` eller `multi_prompt`. Brug @Image1, @Video1, @Element1 osv. til at referere til angivne input. |
| `multi_prompt` |  | array of object {prompt, duration} \| null | no |  | ≥ 1 items | Genereringsinstruktioner for hver optagelse, hvor hver prompt definerer én optagelse, hvis varighed bidrager til videoens samlede længde. |
| `multi_prompt[].prompt` |  | string | yes |  | 1 – 512 characters | Tekstinstruktioner for den aktuelle optagelse. |
| `multi_prompt[].duration` |  | integer | no | `5` | 1 – 30 | Varigheden af en individuel optagelse målt i sekunder. |
| `duration` |  | integer | no | `5` | 3 – 30 | Videoens længde i sekunder, fra 3 til 30. |
| `start_image_url` | `image` | string (image URL) \| null | no |  |  | Valgfrit billede til første frame, som tæller med i grænsen for billedreferencer. Maksimal filstørrelse er 30.0 MB; bredde og højde skal hver være mindst 300 px, med et formatforhold mellem 0.40 og 2.50. |
| `image_urls` | `images` | array of image URL \| null | no |  | ≤ 10 items | Billedreferencer adresseret med @Image1, @Image2 osv., med højst 10 billeder. Hver fil er begrænset til 30.0 MB, kræver mindst 300 px i begge dimensioner og skal have et formatforhold mellem 0.40 og 2.50. |
| `video_urls` | `videos` | array of video URL \| null | no |  | ≤ 5 items | Op til 5 referencevideoer adresseret med @Video1, @Video2 osv.; hver varer 3–30 sekunder (højst 30.05 sekunder), og deres samlede varighed sammen med elementvideoer må ikke overstige 30 sekunder. Hver fil må højst være 300 MB, med bredde og højde mellem 700 px og 4553 px. Formatforholdet skal være mellem 0.40 og 2.50 og billedhastigheden mellem 23.9 og 60.05 FPS. |
| `elements` |  | array of object {frontal_image_url, reference_image_urls, video_url, voice_id} \| null | no |  | ≤ 7 items | Samling af op til 7 figurer eller objekter, hvoraf højst 3 må indeholde en `voice_id`, og højst 3 må bruge video. Adresser disse elementer som @Element1, @Element2 osv. |
| `elements[].frontal_image_url` |  | string (image URL) \| null | no |  |  | Frontalt billede, der viser elementets primære visning. Maksimal filstørrelse er 30.0 MB; begge dimensioner skal være mindst 300 px, og formatforholdet skal være mellem 0.40 og 2.50. |
| `elements[].reference_image_urls` |  | array of image URL \| null | no |  | ≤ 3 items | Supplerende billeder, der viser forskellige vinkler af elementet, med 1 til 3 visninger. Hver fil må højst være 30.0 MB, skal måle mindst 300 px i begge dimensioner og have et formatforhold mellem 0.40 og 2.50. |
| `elements[].video_url` |  | string (video URL) \| null | no |  |  | Videorepræsentation af et element i stedet for billeder, med en varighed på 3–30 sekunder (højst 30.05 sekunder). Filen må ikke overstige 300 MB; bredde og højde skal begge være mellem 700–4553 px. Understøttede formatforhold spænder fra 0.40–2.50, med billedhastigheder på 23.9–60.05 FPS. |
| `elements[].voice_id` |  | string \| null | no |  |  | Stemme tildelt elementet. |
| `resolution` |  | enum (string) | no | `1080p` | `720p`, `1080p` | Outputtets opløsning. |
| `aspect_ratio` |  | enum (string) | no | `16:9` | `auto`, `16:9`, `9:16`, `1:1`, `21:9` | Videoens proportioner, valgt eksplicit eller udledt af referencerne ved at vælge '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 produceret af modellen. |

## 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