# Kling 4.0 Reference to Video API

> Ustvari 3–30-sekundne videoposnetke, ki ohranijo videz do 10 referenčnih slik, 5 referenčnih videoposnetkov in 7 elementov

Ustvari videoposnetek iz besedilnega `prompt` ter referenčnih slik, referenčnih videoposnetkov in elementov likov ali predmetov, ki so v pozivu navedeni kot @Image1, @Video1 ali @Element1. Trajanje je od 3 do 30 sekund (privzeto 5), izhod pa je v ločljivosti 720p ali 1080p in z razmerjem stranic auto, 16:9, 9:16, 1:1 ali 21:9. Za pozive za posamezne kadre uporabite `multi_prompt`; v tem primeru je skupna dolžina enaka vsoti trajanj kadrov. Omejitve so 10 slik, 5 videoposnetkov, dolgih po 3–30 s, in 7 elementov, od katerih imajo lahko največ 3 glas.

- 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/sl/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 | Navodila za generiranje, ki izpolnjujejo zahtevo po posredovanju `prompt` ali `multi_prompt`. Za sklicevanje na posredovane vhode uporabite @Image1, @Video1, @Element1 in tako naprej. |
| `multi_prompt` |  | array of object {prompt, duration} \| null | no |  | ≥ 1 items | Navodila za generiranje po kadrih, pri katerih vsak poziv določa en kader, njegovo trajanje pa prispeva k skupni dolžini videa. |
| `multi_prompt[].prompt` |  | string | yes |  | 1 – 512 characters | Besedilna navodila za trenutni kader. |
| `multi_prompt[].duration` |  | integer | no | `5` | 1 – 30 | Trajanje posameznega kadra, merjeno v sekundah. |
| `duration` |  | integer | no | `5` | 3 – 30 | Dolžina videa v sekundah, od 3 do 30. |
| `start_image_url` | `image` | string (image URL) \| null | no |  |  | Izbirna slika prve sličice, ki se šteje v omejitev referenc slik. Največja velikost datoteke je 30.0 MB; širina in višina morata biti dolgi najmanj 300 px, razmerje stranic pa mora biti med 0.40 in 2.50. |
| `image_urls` | `images` | array of image URL \| null | no |  | ≤ 10 items | Reference slik, naslovljene z @Image1, @Image2 in tako naprej, z največ 10 slikami. Vsaka datoteka je omejena na 30.0 MB, obe dimenziji morata biti dolgi najmanj 300 px, razmerje stranic pa mora biti med 0.40 in 2.50. |
| `video_urls` | `videos` | array of video URL \| null | no |  | ≤ 5 items | Do 5 referenčnih videov, naslovljenih z @Video1, @Video2 in tako naprej; vsak traja 3–30 sekund (največ 30.05 sekunde), njihovo skupno trajanje skupaj z videi elementov pa ne sme preseči 30 sekund. Vsaka datoteka je lahko velika največ 300 MB, širina in višina pa morata biti med 700 px in 4553 px. Razmerje stranic mora biti med 0.40 in 2.50, hitrost sličic pa med 23.9 in 60.05 FPS. |
| `elements` |  | array of object {frontal_image_url, reference_image_urls, video_url, voice_id} \| null | no |  | ≤ 7 items | Zbirka do 7 likov ali predmetov, od katerih lahko največ 3 vključujejo `voice_id` in največ 3 uporabljajo video. Te elemente naslovite z @Element1, @Element2 in tako naprej. |
| `elements[].frontal_image_url` |  | string (image URL) \| null | no |  |  | Čelna slika glavnega pogleda elementa. Največja velikost datoteke je 30.0 MB; obe dimenziji morata biti dolgi najmanj 300 px, razmerje stranic pa mora biti med 0.40 in 2.50. |
| `elements[].reference_image_urls` |  | array of image URL \| null | no |  | ≤ 3 items | Dodatne slike različnih kotov elementa, z 1 do 3 pogledi. Vsaka datoteka je lahko velika največ 30.0 MB, obe dimenziji morata biti dolgi najmanj 300 px, razmerje stranic pa mora biti med 0.40 in 2.50. |
| `elements[].video_url` |  | string (video URL) \| null | no |  |  | Video, ki predstavlja element namesto slik, dolg 3–30 sekund (največ 30.05 sekunde). Datoteka ne sme presegati 300 MB; širina in višina morata biti med 700–4553 px. Podprta razmerja stranic so 0.40–2.50, hitrost sličic pa 23.9–60.05 FPS. |
| `elements[].voice_id` |  | string \| null | no |  |  | Glas, dodeljen elementu. |
| `resolution` |  | enum (string) | no | `1080p` | `720p`, `1080p` | Ločljivost izhoda. |
| `aspect_ratio` |  | enum (string) | no | `16:9` | `auto`, `16:9`, `9:16`, `1:1`, `21:9` | Razmerja videa, izbrano izrecno ali izpeljano iz referenc z izbiro '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, ki ga ustvari model. |

## 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