Kling V4 Video Generation

curl --request POST \
  --url https://api.apimart.ai/v1/videos/generations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
    "model": "kling-v4",
    "prompt": "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
    "duration": 5,
    "resolution": "720p",
    "aspect_ratio": "9:16"
  }'

import requests

response = requests.post(
    "https://api.apimart.ai/v1/videos/generations",
    headers={"Authorization": "Bearer <token>"},
    json={
        "model": "kling-v4",
        "prompt": "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
        "duration": 5,
        "resolution": "720p",
        "aspect_ratio": "9:16"
    }
)
response.raise_for_status()
print(response.json())

const response = await fetch("https://api.apimart.ai/v1/videos/generations", {
  method: "POST",
  headers: {
    Authorization: "Bearer <token>",
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    model: "kling-v4",
    prompt: "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
    duration: 5,
    resolution: "720p",
    aspect_ratio: "9:16"
  })
});
if (!response.ok) throw new Error(await response.text());
console.log(await response.json());

POST

videos

generations

curl --request POST \
  --url https://api.apimart.ai/v1/videos/generations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
    "model": "kling-v4",
    "prompt": "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
    "duration": 5,
    "resolution": "720p",
    "aspect_ratio": "9:16"
  }'

import requests

response = requests.post(
    "https://api.apimart.ai/v1/videos/generations",
    headers={"Authorization": "Bearer <token>"},
    json={
        "model": "kling-v4",
        "prompt": "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
        "duration": 5,
        "resolution": "720p",
        "aspect_ratio": "9:16"
    }
)
response.raise_for_status()
print(response.json())

const response = await fetch("https://api.apimart.ai/v1/videos/generations", {
  method: "POST",
  headers: {
    Authorization: "Bearer <token>",
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    model: "kling-v4",
    prompt: "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
    duration: 5,
    resolution: "720p",
    aspect_ratio: "9:16"
  })
});
if (!response.ok) throw new Error(await response.text());
console.log(await response.json());

This endpoint is asynchronous. After submission, use the returned task_id with GET /v1/videos/generations/{task_id} to query the task status and result.

curl --request POST \
  --url https://api.apimart.ai/v1/videos/generations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
    "model": "kling-v4",
    "prompt": "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
    "duration": 5,
    "resolution": "720p",
    "aspect_ratio": "9:16"
  }'

import requests

response = requests.post(
    "https://api.apimart.ai/v1/videos/generations",
    headers={"Authorization": "Bearer <token>"},
    json={
        "model": "kling-v4",
        "prompt": "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
        "duration": 5,
        "resolution": "720p",
        "aspect_ratio": "9:16"
    }
)
response.raise_for_status()
print(response.json())

const response = await fetch("https://api.apimart.ai/v1/videos/generations", {
  method: "POST",
  headers: {
    Authorization: "Bearer <token>",
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    model: "kling-v4",
    prompt: "A paper boat drifts along a gutter on a rainy night, with the gentle sound of rain",
    duration: 5,
    resolution: "720p",
    aspect_ratio: "9:16"
  })
});
if (!response.ok) throw new Error(await response.text());
console.log(await response.json());

Mode selection

All five modes use the same model name, kling-v4. The mode is selected from the supplied assets and omni_reference_task_type.

Mode	Input
Text-to-video	No image, video, or audio assets
Image-to-video	A first frame, optionally a last frame and up to 8 intermediate frames
Reference-based generation	Supply `video_urls`, `audio_urls`, or `reference_image` in `image_with_roles`; alternatively, explicitly set `omni_reference_task_type: "reference"`
Video editing	Set `omni_reference_task_type: "edit"` and supply an input video
Video extension	Set `omni_reference_task_type: "extend"` and supply an input video

omni_reference_task_type defaults to auto, equivalent to omitting it. When explicitly set to reference, images in image_urls are treated as reference images.

Supplying only video_url without specifying edit or extend returns HTTP 400. To use a video as a reference asset, use video_urls.

Request headers

string

required

Bearer authentication: Bearer <token>, where <token> is your APIMart API Key.

Request parameters

string

required

Must be kling-v4.

string

Describe the content to generate or edit. Optional for image-to-video; required for all other modes.In reference-based generation, use @Image1, @Video1, and @Audio1 to refer to assets, numbered from 1 in each asset array. In video editing, the input video is @Video1, and reference images are @Image1, @Image2, and so on.

integer

Generated duration in seconds, from 3 to 30; default: 5.

Video editing: when omitted, the output duration follows the input video.
Video extension: the duration of the new segment. The returned video combines the original video and the new segment.

string

default:"720p"

Output resolution: 720p or 1080p. Use this field to select the resolution; V4 does not support mode.

string

Supports 16:9, 9:16, 1:1, and 21:9. Reference-based generation also supports auto.

Mode	Default behavior
Text-to-video	`16:9`
Image-to-video	Follows the first frame
Reference-based generation	`auto`
Video editing	Follows the input video
Video extension	This field is not supported; the original aspect ratio is preserved

string[]

Image URL list, interpreted according to the mode:

Image-to-video: the first image is the first frame and the second is the last frame; up to 2 images.
Reference-based generation and video editing: up to 10 reference images. For generation using only reference images, explicitly set omni_reference_task_type: "reference".

Asset URLs must be publicly accessible.

object[]

Image list with roles. Each item contains url and role.

`role`	Purpose
`first_frame`	First frame for image-to-video; exactly 1 required
`last_frame`	Last frame for image-to-video, or target last frame for extension
`keyframe`	Intermediate frame for image-to-video; `middle_frame` is also accepted. Used in array order, up to 8 images
`reference_image`	Reference image for reference-based generation

For image-to-video, the first frame, last frame, and intermediate frames must total no more than 10 images.

string

First-frame image URL for image-to-video. It can also be supplied as first_frame in image_with_roles, or as the first image in image_urls.

string

Last-frame image URL for image-to-video, or target last-frame image URL for extension.

string[]

Reference videos for reference-based generation: up to 5 clips, using no more than 30 seconds in total.For video editing or extension, you may instead supply exactly 1 video URL in place of video_url, with omni_reference_task_type: "edit" or "extend".

string

Input video URL for editing or extension. Requires omni_reference_task_type: "edit" or "extend".For editing, the input video must be at least 3 seconds; shorter videos return HTTP 400. Videos longer than 30 seconds are trimmed to the first 30 seconds.

string[]

Reference audio for reference-based generation: up to 3 clips, each 5–30 seconds long.Reference images, videos, and audio combined must total no more than 15 assets for reference-based generation.

string

default:"auto"

Supports auto, reference, edit, and extend.

auto: selects text-to-video, image-to-video, or reference-based generation from the assets; equivalent to omitting the field.
reference: reference-based generation; images in image_urls are treated as references.
edit: video editing; requires an input video.
extend: video extension; requires an input video.

string

Supports origin (preserve input video audio) and auto (generate new audio). Only for video editing or reference-based generation with reference videos.

Video editing: preserves the original audio by default; auto generates new audio.
Reference-based generation with reference videos: generates new audio by default; origin preserves reference video audio.
Video extension: this field is not supported. Original audio is preserved, and audio is generated automatically for the new segment.

V4 always outputs video with stereo audio, generating sound together with the visuals.

Request examples

Asset URLs below are placeholders. Replace them with real, publicly accessible URLs.

Image-to-video: first and last frames

{
  "model": "kling-v4",
  "prompt": "The camera slowly moves closer",
  "image_urls": ["https://example.com/start.png", "https://example.com/end.png"]
}

The first image is the first frame, and the second is the last frame. prompt is optional for image-to-video.

Image-to-video: first, intermediate, and last frames

{
  "model": "kling-v4",
  "prompt": "A girl walks from the window to the door, then looks back and smiles",
  "image_with_roles": [
    {"url": "https://example.com/1.png", "role": "first_frame"},
    {"url": "https://example.com/2.png", "role": "keyframe"},
    {"url": "https://example.com/3.png", "role": "keyframe"},
    {"url": "https://example.com/4.png", "role": "last_frame"}
  ],
  "duration": 10
}

Intermediate frames are used in array order. Exactly 1 first frame is required, with no more than 10 images across the first, last, and intermediate frames.

Reference-based generation

{
  "model": "kling-v4",
  "prompt": "The girl in @Image1 runs along the beach with the camera movement from @Video1 and background music from @Audio1",
  "image_with_roles": [
    {"url": "https://example.com/girl.png", "role": "reference_image"}
  ],
  "video_urls": ["https://example.com/camera.mp4"],
  "audio_urls": ["https://example.com/bgm.mp3"],
  "aspect_ratio": "auto",
  "duration": 5
}

Up to 10 reference images, 5 reference videos, and 3 reference audio clips, with no more than 15 assets combined. Reference videos use up to 30 seconds in total; each reference audio clip must be 5–30 seconds.

Video editing

{
  "model": "kling-v4",
  "prompt": "Change the scene to a snowy winter night",
  "omni_reference_task_type": "edit",
  "video_url": "https://example.com/in.mp4",
  "image_urls": ["https://example.com/style.png"]
}

The input video must be at least 3 seconds; videos longer than 30 seconds are trimmed to the first 30 seconds. If duration and aspect_ratio are omitted, the output follows the input video. Original audio is preserved by default; use audio_setting: "auto" to generate new audio.

Video extension

{
  "model": "kling-v4",
  "prompt": "The camera continues moving forward as the sky grows darker",
  "omni_reference_task_type": "extend",
  "video_url": "https://example.com/in.mp4",
  "duration": 5
}

Extension starts from the final frame of the input video. The result combines the original video and the new segment; only the new segment duration is billed. Supply a target last frame with last_frame_image or last_frame in image_with_roles. Extension does not support aspect_ratio or audio_setting.

Query a task

Replace the task ID in the following request with the ID returned on submission:

curl --request GET \
  --url 'https://api.apimart.ai/v1/videos/generations/<task_id>' \
  --header 'Authorization: Bearer <token>'

Approximate generation time: 3 minutes for a 3-second 720p video, and 3.5 minutes for a 15-second video.

Billing

Billed per second. See Model Pricing for rates. 720p and 1080p are priced separately. Video editing and reference-based generation with reference videos use the video-input rate. Other modes use the standard generation rate.

Mode	Billable seconds
Text-to-video, image-to-video, reference-based generation with only images or audio	Output seconds
Video extension	New segment seconds
Video editing, reference-based generation with reference videos	Output seconds + max(output seconds, input video seconds)

Input video seconds are calculated by summing clip durations, rounding up to a whole second, and capping at 30 seconds. For example, editing a 3.04-second video without duration produces 4 seconds, billed as 4 + 4 = 8 seconds. For editing and reference-based generation with reference videos, input video duration is probed at submission. A probe failure returns HTTP 400 without charging. Failed generations receive a full refund.

Unsupported parameters

The following parameters or values return HTTP 400:

mode: V4 has no std, pro, or 4k tiers. Use resolution.
negative_prompt, watermark: true, audio: false.
multi_shot, multi_prompt, element_list, video_list.
camera_control, voice_list.

Common errors

Error	Action
`video_url needs omni_reference_task_type edit ... or extend`	Explicitly specify `edit` or `extend` when using `video_url`; use `video_urls` for reference videos
`image-to-video requires exactly 1 first frame`	Supply exactly 1 first frame; last or intermediate frames alone are not sufficient
`first frame, last frame and keyframes together are at most 10 images`	Reduce the total number of first, last, and intermediate frames to at most 10
`reference images, videos and audios together are at most 15 files`	Reduce the total number of reference assets to at most 15
`video edit requires an input video of at least 3 seconds`	Use an input video of at least 3 seconds
`Failed to probe the input video duration`	Check that the URL is accessible and points to a valid video file
`has no std/pro/4k mode`	Remove `mode` and use `resolution`
`Could not download the input from ... (HTTP 403)`	Use a publicly accessible asset URL without hotlink protection

Overview

Models

Text Series

Image Series

Video Series

Audio Series

Moderation Series

Upload Management

Task Management

Account Management

Kling V4 Video Generation

Mode selection

Request headers

Request parameters

Request examples

Image-to-video: first and last frames

Image-to-video: first, intermediate, and last frames

Reference-based generation

Video editing

Video extension

Query a task

Billing

Unsupported parameters

Common errors

​Mode selection

​Request headers

​Request parameters

​Request examples

​Image-to-video: first and last frames

​Image-to-video: first, intermediate, and last frames

​Reference-based generation

​Video editing

​Video extension

​Query a task

​Billing

​Unsupported parameters

​Common errors

Mode selection

Request headers

Request parameters

Request examples

Image-to-video: first and last frames

Image-to-video: first, intermediate, and last frames

Reference-based generation

Video editing

Video extension

Query a task

Billing

Unsupported parameters

Common errors