# Veo 3.1 Fast API

> Veo 3.1 nhanh hơn, chi phí thấp hơn cho clip 4 đến 8 giây có âm thanh.

Veo 3.1 Fast duy trì độ chân thực, hội thoại và khả năng tạo âm thanh của Veo với thời gian kết xuất ngắn hơn và mức giá thấp hơn nhiều, phù hợp làm mặc định để lặp lại. 4, 6 hoặc 8 giây, 16:9 hoặc 9:16, ở 720p, 1080p hoặc 4K; có thể tắt âm thanh.

- Model id: `veo3.1/fast`
- Made by: Google
- Category: Text to Video
- Output: video
- Price: from $0.10 / second (8 s ≈ $0.80) (cheapest run $0.80 (800 API credits))
- Run: `POST https://api.doitong.com/v1/run/veo3.1/fast`
- Quote: `POST https://api.doitong.com/v1/quote/veo3.1/fast`
- Docs page: https://doitong.com/vi/developers/models/veo3.1/fast

## Pricing

Price: **from $0.10 / second (8 s ≈ $0.80)** (the lowest tier; the quote prices your exact input). Billed per second of output (`duration`, default 8).

Price rules (the first rule that matches the input wins; a parameter you leave out counts as its default):

- When `resolution` = 4k and `generate_audio` = true: $0.35 (350 API credits) / second
- When `resolution` = 4k: $0.30 (300 API credits) / second
- When `generate_audio` = true: $0.15 (150 API credits) / second

The full example input below costs $0.90 = 900 API credits (6 s × 150 API credits).

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/veo3.1/fast` 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

| Parameter | Canonical name | Type | Required | Default | Allowed values / range | Description |
|---|---|---|---|---|---|---|
| `prompt` |  | string | yes |  | ≤ 20000 characters | Mô tả bằng văn bản về video mong muốn để tạo sinh. |
| `aspect_ratio` |  | enum (string) | no | `16:9` | `16:9`, `9:16` | Tỷ lệ chiều rộng trên chiều cao của video được tạo sinh. |
| `duration` |  | enum (string) | no | `8s` | `4s`, `6s`, `8s` | Độ dài video đầu ra. |
| `negative_prompt` |  | string \| null | no |  |  | Lời nhắc phủ định dùng để định hướng tạo sinh video. |
| `resolution` |  | enum (string) | no | `720p` | `720p`, `1080p`, `4k` | Độ phân giải được sử dụng cho video đầu ra. |
| `generate_audio` |  | boolean | no | `true` |  | Kiểm soát việc video có bao gồm âm thanh được tạo hay không. |
| `seed` |  | integer \| null | no |  |  | Giá trị seed khởi tạo quá trình tạo số ngẫu nhiên. |
| `auto_fix` |  | boolean | no | `true` |  | Tự động viết lại lời nhắc nhằm cố gắng khắc phục lỗi trong kiểm tra chính sách nội dung hoặc quá trình xác thực khác. |
| `safety_tolerance` |  | enum (string) | no | `4` | `1`, `2`, `3`, `4`, `5`, `6` | Đặt mức dung sai kiểm duyệt nội dung từ mức ít hạn chế nhất, 6, đến mức nghiêm ngặt nhất, 1, vốn chặn hầu hết nội dung. |

## Example input

Required parameters only:

```json
{
  "prompt": "A golden retriever runs along a beach at sunset, waves splashing, slow motion, warm backlight"
}
```

A fuller example:

```json
{
  "prompt": "A golden retriever runs along a beach at sunset, waves splashing, slow motion, warm backlight",
  "duration": 6,
  "resolution": "720p"
}
```

## 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/veo3.1/fast?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A golden retriever runs along a beach at sunset, waves splashing, slow motion, warm backlight",
    "duration": 6,
    "resolution": "720p"
  }'

# 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/veo3.1/fast?wait=20", {
  method: "POST",
  headers,
  body: JSON.stringify({
    "prompt": "A golden retriever runs along a beach at sunset, waves splashing, slow motion, warm backlight",
    "duration": 6,
    "resolution": "720p"
  }),
});
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 golden retriever runs along a beach at sunset, waves splashing, slow motion, warm backlight",
    "duration": 6,
    "resolution": "720p",
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/veo3.1/fast", 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": "veo3.1/fast",
      "input": {
        "prompt": "A golden retriever runs along a beach at sunset, waves splashing, slow motion, warm backlight",
        "duration": 6,
        "resolution": "720p"
      },
      "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": "veo3.1/fast",
  "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": 900,
    "usd": "0.90",
    "charged": 900,
    "refunded": 0
  },
  "input": {
    "prompt": "A golden retriever runs along a beach at sunset, waves splashing, slow motion, warm backlight",
    "duration": 6,
    "resolution": "720p"
  },
  "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 do mô hình tạo ra. |

## Related models

- [Veo 3.1](https://doitong.com/developers/models/veo3.1.md) (`veo3.1`): from $0.20 / second
- [Veo 3.1 Fast Image to Video](https://doitong.com/developers/models/veo3.1/fast/image-to-video.md) (`veo3.1/fast/image-to-video`): from $0.10 / second
- [Veo 3.1 Image to Video](https://doitong.com/developers/models/veo3.1/image-to-video.md) (`veo3.1/image-to-video`): from $0.20 / second
- [Veo3.1 Fast First Last Frame to Video](https://doitong.com/developers/models/veo3.1/fast/first-last-frame-to-video.md) (`veo3.1/fast/first-last-frame-to-video`): from $0.10 / second
- [Veo3.1 First Last Frame to Video](https://doitong.com/developers/models/veo3.1/first-last-frame-to-video.md) (`veo3.1/first-last-frame-to-video`): from $0.20 / second
- [Veo3.1 Reference to Video](https://doitong.com/developers/models/veo3.1/reference-to-video.md) (`veo3.1/reference-to-video`): from $0.20 / second
- [FLUX 3 Max Text to Video](https://doitong.com/developers/models/blackforestlabs/flux-3-max/text-to-video.md) (`blackforestlabs/flux-3-max/text-to-video`): from $0.0425 / second of output video
- [Grok Imagine Video 1.5 Text to Video](https://doitong.com/developers/models/xai/grok-imagine-video/v1.5/text-to-video.md) (`xai/grok-imagine-video/v1.5/text-to-video`): from $0.08 / second

## Links

- HTML page: https://doitong.com/developers/models/veo3.1/fast
- 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=veo3.1/fast
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.com/v1/models/veo3.1/fast