> ## Documentation Index > Fetch the complete documentation index at: https://docs.modellix.ai/llms.txt > Use this file to discover all available pages before exploring further. # Veo 3.1 I2V > [Core Function] Veo 3.1 I2V is Google's cinematic image-to-video generation model. [Strengths] It generates high-fidelity 4K video from a starting image. It supports advanced features like first-and-last frame conditioning and referencing up to three images. [Best For] Highly recommended for: animating concept art, creating cinematic transitions between images, and high-end video production. [Limitations] When using first+last frame or reference-only modes, the `duration` parameter must strictly be 8. Negative prompts are not supported in reference-only mode. [Routing] Use this model by default for high-quality image-to-video tasks or when multiple reference images are provided. ## OpenAPI ````yaml /model-api/google/google-i2v.json post /google/veo-3.1-i2v openapi: 3.1.0 info: description: The image-to-video models API from Google (Veo series). version: 1.0.0 contact: name: Modellix Support email: support@modellix.ai title: Google Image-to-Video Models API servers: - url: https://api.modellix.ai/api/v1 description: The image-to-video models API from Google. security: - bearerAuth: [] paths: /google/veo-3.1-i2v: post: summary: Veo 3.1 I2V description: >- [Core Function] Veo 3.1 I2V is Google's cinematic image-to-video generation model. [Strengths] It generates high-fidelity 4K video from a starting image. It supports advanced features like first-and-last frame conditioning and referencing up to three images. [Best For] Highly recommended for: animating concept art, creating cinematic transitions between images, and high-end video production. [Limitations] When using first+last frame or reference-only modes, the `duration` parameter must strictly be 8. Negative prompts are not supported in reference-only mode. [Routing] Use this model by default for high-quality image-to-video tasks or when multiple reference images are provided. operationId: veo31I2VAsync requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/Veo31I2VRequest' examples: image_mode_basic: summary: Image mode — basic image animation value: prompt: The character waves and smiles at the camera image: https://example.com/frame.jpg image_mode_options: summary: Image mode — with optional parameters value: prompt: Smooth transition from day to night image: https://example.com/frame.jpg aspectRatio: '16:9' duration: '8' resolution: 1080p image_mode_last_frame: summary: >- Image mode — image + lastFrame + negativePrompt (duration must be 8) value: prompt: Smooth transition from day to night image: https://example.com/frame.jpg lastFrame: https://example.com/last-frame.jpg negativePrompt: blurry, low quality duration: '8' reference_mode: summary: >- Reference mode — reference images (negativePrompt not supported; duration must be 8) value: prompt: Keep the same character and visual style referenceImages: - https://example.com/frame.jpg aspectRatio: '16:9' duration: '8' resolution: 720p image_mode_portrait: summary: Image mode — portrait orientation with 4K value: prompt: Camera slowly zooms in on the subject image: https://example.com/frame.jpg aspectRatio: '9:16' duration: '8' resolution: 4k personGeneration: allow_adult responses: '200': description: Task submitted successfully content: application/json: schema: $ref: '#/components/schemas/AsyncTaskResponse' example: code: 0 message: success data: status: pending task_id: task-i2v001 model_id: google/veo-3.1-i2v get_result: method: GET url: https://api.modellix.ai/api/v1/tasks/task-i2v001 '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '429': $ref: '#/components/responses/TooManyRequests' '500': $ref: '#/components/responses/InternalServerError' components: schemas: Veo31I2VRequest: description: >- 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. oneOf: - $ref: '#/components/schemas/Veo31I2VImageOption' title: Option 1 — Image mode description: Animate from a starting frame, optionally to an end frame. - $ref: '#/components/schemas/Veo31I2VReferenceOption' title: Option 2 — Reference mode description: Guide generation with reference images (style/character/visual). AsyncTaskResponse: type: object required: - code - message - data properties: code: type: integer description: Response code, 0 indicates success example: 0 message: type: string description: Response message example: success data: type: object required: - status - task_id - model_id properties: status: type: string enum: - pending - processing description: Task status example: pending task_id: type: string description: Unique task identifier for polling example: task-abc123 model_id: type: string description: Model ID in `provider/model` format example: google/veo-3.1-i2v get_result: type: object description: API information to query the task result properties: method: type: string description: HTTP method example: GET url: type: string description: Full URL to query the task result example: https://api.modellix.ai/api/v1/tasks/task-abc123 description: Detailed data about the submitted asynchronous task. Veo31I2VImageOption: type: object required: - prompt - image description: >- Veo 3.1 / Veo 3.1 Fast I2V — image mode. Animate from a starting frame. Cannot be combined with `referenceImages`. properties: prompt: type: string description: Video description text guiding the animation minLength: 1 example: The character waves and smiles at the camera image: type: string description: >- Starting frame. Accepts an image URL (e.g. `https://example.com/frame.jpg`). example: https://example.com/frame.jpg lastFrame: type: string description: >- End frame. Accepts an image URL. Constraint: `duration` must be `8` when using this parameter. example: https://example.com/last-frame.jpg negativePrompt: type: string description: Text describing what to avoid in the generated video. example: blurry, low quality, distorted aspectRatio: type: string description: Video aspect ratio default: '16:9' enum: - '16:9' - '9:16' example: '16:9' duration: type: string description: >- 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. enum: - '4' - '6' - '8' example: '8' resolution: type: string description: >- Video resolution. Constraint: 1080p and 4k are only available when `duration` is `8`. enum: - 720p - 1080p - 4k example: 1080p personGeneration: type: string description: Person generation policy enum: - allow_adult example: allow_adult Veo31I2VReferenceOption: type: object required: - prompt - referenceImages description: >- Veo 3.1 / Veo 3.1 Fast I2V — reference mode. Guide generation with reference images. Cannot be combined with `image`, `lastFrame`, or `negativePrompt`. properties: prompt: type: string description: Video description text guiding the animation minLength: 1 example: The character waves and smiles at the camera referenceImages: type: array description: >- Reference images for style/character/visual guidance (up to 3). Each item is an image URL (e.g. `https://example.com/ref.jpg`). Supported only by Veo 3.1 and Veo 3.1 Fast I2V. items: type: string maxItems: 3 example: - https://example.com/ref.jpg aspectRatio: type: string description: Video aspect ratio default: '16:9' enum: - '16:9' - '9:16' example: '16:9' duration: type: string description: >- Video duration in seconds (string type). Constraint: Must be `8` in reference mode — values `4` or `6` will be rejected by Google. enum: - '8' example: '8' resolution: type: string description: >- Video resolution. Constraint: 1080p and 4k are only available when `duration` is `8`. enum: - 720p - 1080p - 4k example: 1080p personGeneration: type: string description: Person generation policy enum: - allow_adult example: allow_adult ErrorResponse: type: object required: - code - message properties: code: type: integer description: Error code (equals HTTP status code) example: 400 message: type: string description: 'Error message in format ''Category: detail''' example: 'Invalid parameters: parameter ''prompt'' is required' responses: BadRequest: description: Invalid request parameters content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: code: 400 message: 'Invalid parameters: parameter ''prompt'' is required' Unauthorized: description: Unauthorized - Invalid or missing API Key content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: code: 401 message: 'Authentication failed: invalid API key' TooManyRequests: description: Too many requests - Rate limit exceeded headers: X-RateLimit-Limit: description: Maximum requests per minute schema: type: integer example: 100 X-RateLimit-Remaining: description: Remaining quota in current window schema: type: integer example: 0 X-RateLimit-Reset: description: Rate limit window reset time (Unix timestamp) schema: type: integer example: 1704067260 content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: code: 429 message: >- Rate limit exceeded: 100 requests per minute, retry after 60 seconds InternalServerError: description: Internal server error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: code: 500 message: Internal server error securitySchemes: bearerAuth: type: http scheme: bearer description: 'API Key authentication. Format: `Bearer YOUR_API_KEY`.' ````