> ## Documentation Index > Fetch the complete documentation index at: https://docs.budgetpixel.com/llms.txt > Use this file to discover all available pages before exploring further. # Generate video with Kling 4.0 > Kuaishou Kling 4.0, with generated sound (dialogue, music and sound effects described in the prompt). One model for text-to-video; keyframes (a first frame and an optional last frame); reference images of characters, products, places or styles; reference videos to take motion, camera work or style from; and editing a video (supply a `video` and describe the change: the output keeps its length and shape). Frames and reference images combine. Name inputs in the prompt by position: @image_1, @image_2, ... (first frame, last frame, then reference images) and @video_1, ... (the video to edit, then reference videos). 720p or 1080p at 24 fps, 3-30 seconds. Billed per second of output: 207 credits at 720p, 310 at 1080p (`resolution_pricing` in GET /v1/models). With any input video the rate is 124 at 720p and 186 at 1080p, for the output plus the longer of the input videos and the output: editing a 5-second clip bills 10 seconds. POST /v1/cost quotes any request exactly. **Asynchronous.** Returns a job `id` (the video is not in this response). Poll [`GET /v1/videos/{id}`](/api-reference/videos/get-video-job-status) until `status` is `succeeded` — the video URL is in that response's `video_url`. Examples, sample output and pricing: [Kling 4.0](https://budgetpixel.com/models/kling-4.0) > **[Kling 4.0 on BudgetPixel](https://budgetpixel.com/models/kling-4.0)** > > Examples, prompts and pricing. ## OpenAPI ````yaml /openapi.yaml post /videos/kling-4.0 openapi: 3.1.0 info: contact: email: support@budgetpixel.com name: BudgetPixel Support description: > The BudgetPixel developer API for programmatic image, video, music and sound-effect generation. Generation is **asynchronous**: you create a job, then poll its status until it reaches a terminal state (`succeeded` / `failed`). You are charged in credits only on success — never for failures, timeouts, or content blocked before generation. **Authentication.** All requests require an API key sent as a bearer token: Authorization: Bearer bpx_live_xxx Create and manage keys from your BudgetPixel account dashboard. The developer API is available on **every paid plan**. On the **Free** plan, API keys can call the free library searches only: `GET /v1/stock/images`, `GET /v1/stock/sound-effects` and `GET /v1/stock/music`. **Pricing.** API usage is metered in credits at each model's published price (see `GET /v1/models`), and your plan's model discounts and active promotions apply to API charges exactly as they do on the web — `POST /v1/cost` quotes your discounted price. Pro and Ultra plans include a daily free-models allowance (a shared pool of free generations per day across qualified image models such as FLUX 2 Klein and Qwen-Image) that covers API requests too — the standard price applies once the day's pool is used. Other promotional free daily generations remain web/app-only. Failed generations are never charged. **Rate limits.** Requests are limited per minute: **600 requests/min per API key** and **1200 requests/min per source IP** (defaults; subject to tuning). Every response carries `X-RateLimit-Limit`, `X-RateLimit-Remaining`, and `X-RateLimit-Reset` (seconds until the window resets). Exceeding a limit returns HTTP `429` with a `Retry-After` header — wait that long before retrying. Rejected requests still count against the window, so a tight retry loop keeps you limited; back off instead. Generation jobs additionally have a per-plan concurrency cap (the same one as the web workshop), independent of these request limits. `POST /v1/uploads` also has a dedicated **60 uploads/min per account** cap (it's free/unmetered) on top of these limits. Every `429` this API returns carries `Retry-After`, including a full concurrency queue (a suggested wait) and the monthly spend limit (seconds until the month resets). **Characters.** Write `@handle` in the prompt of an image or video generation to cast a character: one of the free BudgetPixel AI influencers (`@barry`, `@rosa`, ...) or a character of your own. Its picture and look go with the mention, so the same face appears in every post. `GET /v1/characters` lists the ones you can cast, `GET /v1/characters/{handle}` gives one in full with every picture, and `POST /v1/characters/recommend` picks influencers for a brief. **Output retention.** Generated files are kept for 24 hours after the job is created. Job status responses give the exact time as `expires_at`; after it, `expired` is `true` and no download URLs are returned. title: BudgetPixel API version: '2026-06-20' servers: - description: Production url: https://api.budgetpixel.com/v1 security: - ApiKeyAuth: [] tags: - description: Account and credit balance name: Account - description: Discover available models and pricing name: Models - description: Upload input media for image/video generation name: Uploads - description: Image job status name: Images - description: FLUX image models name: Black Forest Labs - description: SeeDream image models name: Bytedance - description: Video job status name: Videos - description: Kuaishou Kling video models name: Kling - description: SeeDance video models name: ByteDance (SeeDance) - description: Music and sound-effect job status name: Audios - description: Music generation models name: Music - description: Text-to-sound-effect models (priced per second) name: Sound Effects - description: >- Image-to-3D models — a picture in, a textured 3D model (GLB, plus FBX/USDZ/STL on Meshy) out name: 3D Models - description: Format conversion for images, video, and audio name: Conversions - description: Publish posts to your BudgetPixel feed and enter clan themes name: Social - description: Cast BudgetPixel AI influencers and your own characters with @mentions name: Characters - description: Content moderation — NSFW rating and CSAM detection name: Moderation - description: Content classification — music genre detection name: Classification - description: >- Search the free stock image library — available on every plan, including Free name: Stock Images - description: >- Search the free sound effect library — available on every plan, including Free name: Stock Sound Effects - description: >- Search the free background music library — available on every plan, including Free name: Stock Music - description: >- Turn a video into a depth map video to guide other video models with its structure and motion name: Depth Maps paths: /videos/kling-4.0: post: tags: - Kling summary: Generate video with Kling 4.0 description: >- Kuaishou Kling 4.0, with generated sound (dialogue, music and sound effects described in the prompt). One model for text-to-video; keyframes (a first frame and an optional last frame); reference images of characters, products, places or styles; reference videos to take motion, camera work or style from; and editing a video (supply a `video` and describe the change: the output keeps its length and shape). Frames and reference images combine. Name inputs in the prompt by position: @image_1, @image_2, ... (first frame, last frame, then reference images) and @video_1, ... (the video to edit, then reference videos). 720p or 1080p at 24 fps, 3-30 seconds. Billed per second of output: 207 credits at 720p, 310 at 1080p (`resolution_pricing` in GET /v1/models). With any input video the rate is 124 at 720p and 186 at 1080p, for the output plus the longer of the input videos and the output: editing a 5-second clip bills 10 seconds. POST /v1/cost quotes any request exactly. **Asynchronous.** Returns a job `id` (the video is not in this response). Poll [`GET /v1/videos/{id}`](/api-reference/videos/get-video-job-status) until `status` is `succeeded` — the video URL is in that response's `video_url`. Examples, sample output and pricing: [Kling 4.0](https://budgetpixel.com/models/kling-4.0) operationId: createVideo_kling_4_0 requestBody: content: application/json: schema: properties: aspect_ratio: default: '16:9' description: >- Aspect ratio for text-to-video and reference-only jobs. A first frame or a video to edit sets the shape and this is ignored. enum: - '16:9' - '9:16' - '1:1' - '21:9' type: string end_image: description: >- Optional last frame, used together with `image`: the video moves from the first frame to this one. Same input forms and limits as `image`. type: string x-bpx-media: image image: description: >- Optional first frame (@image_1): the video starts from it and takes its shape. Provide a public image URL, a data URI, raw base64, or an uploaded-file URL from POST /v1/uploads. JPG or PNG, at least 300px on each side, aspect ratio between 2:5 and 5:2. Can't be combined with `video`. type: string x-bpx-media: image length_seconds: default: 5 description: >- Video length in seconds, any whole number from 3 to 30. Ignored when editing a `video` (the output keeps its length). maximum: 30 minimum: 3 type: integer prompt: description: >- Text description of the video, including the sound you want, or the change to make when editing a `video`. Name inputs by position: @image_1, @image_2, ... (first frame, last frame, then reference images) and @video_1, @video_2, ... (the video to edit, then reference videos). Write `@handle` to cast a character: a BudgetPixel AI influencer or one of your own ([`GET /v1/characters`](/api-reference/characters/list-characters-you-can-cast)). type: string reference_images: description: >- Optional reference images of characters, products, places or styles, named in the prompt as @image_N (numbered after `image` and `end_image`). Up to 10 images in all, counting `image` and `end_image`. Same input forms and limits as `image`. No extra charge. items: type: string maxItems: 10 type: array x-bpx-media: image reference_videos: description: >- Optional reference videos to take motion, camera work or style from, named in the prompt as @video_N (numbered after `video`). MP4 or MOV, 3-30 seconds each, 700-4553 pixels on each side, aspect ratio between 2:5 and 5:2, up to 100MB each; up to 5 videos and 30 seconds in all, counting `video`. Each item is a public video URL or an uploaded-file URL from POST /v1/uploads. Any input video moves the job to the video-input rate, billed for the output plus the longer of the input videos and the output: see POST /v1/cost. items: type: string maxItems: 5 type: array x-bpx-media: video resolution: default: 720p description: >- Output resolution, 720p or 1080p. Sets the price per second: see `resolution_pricing` in GET /v1/models. enum: - 720p - 1080p type: string video: description: >- Optional video to EDIT (@video_1): describe the change in `prompt`. The output keeps the clip's length and aspect ratio, so `length_seconds` and `aspect_ratio` are ignored. Same limits as `reference_videos`; can't be combined with `image` or `end_image`. Billed at the video-input rate for twice the clip's length in whole seconds (plus any reference videos). type: string x-bpx-media: video required: - prompt type: object required: true responses: '200': content: application/json: schema: $ref: '#/components/schemas/CreateVideoResponse' description: Job accepted. '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '429': $ref: '#/components/responses/TooManyRequests' components: schemas: CreateVideoResponse: properties: characters: description: >- The characters the prompt cast with `@handle` mentions. Absent when none. items: $ref: '#/components/schemas/CharacterCredit' type: array id: description: Opaque job id — use it to poll status. type: string message: type: string model: type: string status: $ref: '#/components/schemas/JobStatus' type: object CharacterCredit: properties: handle: example: barry type: string name: example: Barry type: string official: description: '`true` for a BudgetPixel AI influencer.' type: boolean page_url: format: uri type: string type: object JobStatus: description: Lifecycle state. `succeeded`/`failed`/`timeout` are terminal. enum: - pending - starting - processing - completing - succeeded - failed - timeout type: string Error: properties: error: properties: code: description: Stable machine-readable code. example: model_not_available type: string message: type: string type: description: Error category. example: invalid_request_error type: string required: - type - code - message type: object required: - error type: object ModerationBlocked: description: >- Returned (with HTTP 400) when the input content moderation gate blocks a generation request. The block is a property of the request's prompt or input media — reword the prompt or change the input and retry. Branch on `restriction_reason`, which is stable and machine-readable. properties: error: description: Human-readable explanation of the block. type: string restriction_reason: description: Stable machine-readable block reason. enum: - input_csam - input_explicit_adult - input_upload_nudity - input_celebrity_likeness - strict_model_nsfw type: string required: - error - restriction_reason type: object QueueFull: description: | `429` body when your account already has as many jobs of this kind (image, video or audio) in flight as its concurrency cap allows. Submit the next job when one of your running jobs finishes. properties: active_jobs: description: Jobs of this kind in flight right now. type: integer code: enum: - queue_full type: string error: description: Human-readable message. type: string queue_full: enum: - true type: boolean queue_limit: description: Your concurrency cap for this kind of job. type: integer retry_after_seconds: description: Same value as the `Retry-After` header. type: integer required: - error - code - queue_full - queue_limit - active_jobs - retry_after_seconds type: object responses: BadRequest: content: application/json: schema: oneOf: - $ref: '#/components/schemas/Error' - $ref: '#/components/schemas/ModerationBlocked' description: >- The request was malformed, referenced an unavailable model, or was blocked by input content moderation (moderation blocks carry a `restriction_reason` — see ModerationBlocked). Unauthorized: content: application/json: schema: $ref: '#/components/schemas/Error' description: Missing or invalid API key. Forbidden: content: application/json: schema: $ref: '#/components/schemas/Error' description: >- Authenticated but not permitted (plan gate, ownership, account restriction). Content-moderation blocks are 400, not 403. TooManyRequests: content: application/json: schema: oneOf: - $ref: '#/components/schemas/Error' - $ref: '#/components/schemas/QueueFull' description: > A limit was reached. Every `429` carries `Retry-After` (seconds). The per-minute rate limit, the upload limit and the hourly API post cap answer with the `Error` envelope, code `rate_limited`. The monthly spend limit answers with code `monthly_spend_limit_reached`, and its `Retry-After` counts down to the start of next month (raising the limit in the console clears it sooner). A full concurrency queue answers with the flat `QueueFull` body (3D jobs: the `Error` envelope with code `queue_full`); its `Retry-After` is a suggested wait, because a slot frees as soon as one of your running jobs finishes. headers: Retry-After: description: Seconds to wait before retrying. schema: minimum: 1 type: integer securitySchemes: ApiKeyAuth: bearerFormat: bpx_live_* description: 'API key as a bearer token: Authorization: Bearer bpx_live_xxx' scheme: bearer type: http ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.