Veo 3.1 Fast I2V - Modellix

curl --request POST \ --url https://api.modellix.ai/api/v1/google/veo-3.1-fast-i2v \ --header 'Authorization: Bearer <token>' \ --header 'Content-Type: application/json' \ --data ' { "prompt": "Gentle breeze causes leaves to rustle in the scene", "image": "https://example.com/frame.jpg" } '

{ "code": 0, "message": "success", "data": { "status": "pending", "task_id": "task-i2v002", "model_id": "google/veo-3.1-fast-i2v", "get_result": { "method": "GET", "url": "https://api.modellix.ai/api/v1/tasks/task-i2v002" } } }

Authorizations

Authorization

string

header

required

API Key authentication. Format: Bearer YOUR_API_KEY.

Body

application/json

Option 1 — Image mode
Option 2 — Reference mode

Veo 3.1 / Veo 3.1 Fast image-to-video request. Choose one option — image mode and referenceImages mode are mutually exclusive. Resolution up to 4K. Constraints verified 2026-04-29 against Google raw API, see each parameter for details.

prompt

string

required

Video description text guiding the animation

Minimum string length: 1

Example:

"The character waves and smiles at the camera"

image

string

required

Starting frame. Accepts an image URL (e.g. https://example.com/frame.jpg).

Example:

"https://example.com/frame.jpg"

lastFrame

string

End frame. Accepts an image URL. Constraint: duration must be 8 when using this parameter.

Example:

"https://example.com/last-frame.jpg"

negativePrompt

string

Text describing what to avoid in the generated video.

Example:

"blurry, low quality, distorted"

aspectRatio

enum<string>

default:16:9

Video aspect ratio

Available options:

16:9,

9:16

Example:

"16:9"

duration

enum<string>

Video duration in seconds (string type). Constraint: When using lastFrame, must be 8 — values 4 or 6 will be rejected by Google. Otherwise 4, 6, 8 are all valid.

Available options:

4,

6,

8

Example:

"8"

resolution

enum<string>

Video resolution. Constraint: 1080p and 4k are only available when duration is 8.

Available options:

720p,

1080p,

4k

Example:

"1080p"

personGeneration

enum<string>

Person generation policy

Available options:

allow_adult

Example:

"allow_adult"

Response

Task submitted successfully

code

integer

required

Response code, 0 indicates success

Example:

0

message

string

required

Response message

Example:

"success"

data

object

required

Detailed data about the submitted asynchronous task.

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