Kling 4.0 Flash Reference To Video API

kwaivgi/kling-v4.0-flash/reference-to-video

Kling V4.0 Flash Reference-to-Video generates high-quality videos guided by reference images and videos, with synchronized audio and a focus on fast generation for character consistency, motion guidance, social content, marketing videos, and production workflows. Ready-to-use REST inference API.

Reference to Video
Input

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preview

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preview

Idle

$0.094per run·~10 / $1

ExamplesView all

Use @Image1 as the female mechanic and @Image2 as the airship captain. Preserve their exact identities, hairstyles, clothing, accessories, and proportions. Opening frame: the female mechanic stands on the left side of the brass engine, body turned three-quarters toward the machinery, one hand resting naturally on a brass valve and the other holding a small wrench near her waist. The airship captain stands slightly behind her on the right, body angled toward the engine, one hand resting on the metal railing while he watches a pressure gauge. Both characters are focused on the machinery, not looking at the camera. The engine suddenly gives a short mechanical shake. The mechanic immediately tightens the valve with one controlled movement. The engine stabilizes. The captain looks from the gauge toward her, and she gives him a brief calm nod. The camera makes one subtle sideways push around both characters while keeping the engine visible. Natural steampunk interaction, restrained body language, realistic character chemistry, detailed brass machinery, cinematic industrial lighting.

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README

Kling V4.0 Flash Reference-to-Video

Kling V4.0 Flash Reference-to-Video generates a 720p video guided by reference images and videos, with synchronized audio. Flash is the fast, lower-cost tier of Kling 4.0: 720p clips of 3 to 20 seconds with synchronized audio, for quick iteration and volume work.

Why Choose This?

  • Consistent subjects — Up to 10 reference images for characters, products or styles.
  • Motion references — Up to 5 reference videos (together up to 20 seconds) for motion, camera and pacing.
  • Keep the original sound — Optionally keep a reference video's own audio.
  • Fast iteration — Flash returns clips quickly.

Parameters

ParameterRequiredDescription
promptYesDescribe the video. Refer to reference images as @Image1, @Image2, ... and to reference videos as @Video1, @Video2, ... in array order.
imagesNoUp to 10 reference images.
videosNoUp to 5 reference videos, together used for up to 20 seconds.
keep_original_soundNoKeep the reference video's own sound instead of generating new audio. Requires videos. Default false.
durationNo3 to 20 seconds, default 5.
aspect_ratioNoauto (default, follows the references), 16:9, 9:16, 1:1 or 21:9.

Pricing

InputsPrice per second of output
Reference images only$0.094
With reference videos$0.126

A 5 second clip costs $0.47 with images only, $0.63 with reference videos.

Related Models

Note:This website uses AI models provided by third parties. Documentation prices are for reference and may be outdated. The Generate button shows an estimate; the final task charge prevails.

Kling v4.0 Flash Reference To Video API — Quick start

Grab a WaveSpeedAI API key, then call POST https://api.wavespeed.ai/api/v3/kwaivgi/kling-v4.0-flash/reference-to-video with your input as JSON. The endpoint returns a prediction id. Start polling the result endpoint around every 2 seconds, increase the interval for long-running tasks, and stop on any terminal status. On completed, read output values from data.outputs. Examples for Kling v4.0 Flash Reference To Video below.

HTTP example
set -euo pipefail

: "${WAVESPEED_API_KEY:?Set WAVESPEED_API_KEY}"

REQUEST_BODY=$(cat <<'JSON'
{
    "prompt": "A cinematic shot of a city at sunset, soft golden light",
    "keep_original_sound": false,
    "duration": 5,
    "aspect_ratio": "auto"
}
JSON
)

# 1. Submit the prediction.
SUBMIT_RESPONSE=$(curl --silent --show-error --fail-with-body \
  -X POST "https://api.wavespeed.ai/api/v3/kwaivgi/kling-v4.0-flash/reference-to-video" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $WAVESPEED_API_KEY" \
  -d "$REQUEST_BODY")

TASK=$(printf '%s' "$SUBMIT_RESPONSE" | jq 'if has("data") then .data else . end')
PREDICTION_ID=$(printf '%s' "$TASK" | jq -r '.id')
if [ -z "$PREDICTION_ID" ] || [ "$PREDICTION_ID" = "null" ]; then
  printf 'Submission response did not contain a prediction id
' >&2
  exit 1
fi
RESULT_URL="https://api.wavespeed.ai/api/v3/predictions/$PREDICTION_ID/result"

# 2. Poll until the prediction finishes.
while true; do
  RESPONSE=$(curl --silent --show-error --fail-with-body "$RESULT_URL" \
    -H "Authorization: Bearer $WAVESPEED_API_KEY")
  RESULT=$(printf '%s' "$RESPONSE" | jq 'if has("data") then .data else . end')
  STATUS=$(printf '%s' "$RESULT" | jq -r '.status')
  case "$STATUS" in
    completed) printf '%s\n' "$RESULT" | jq '.outputs'; break ;;
    failed|cancelled|timeout|deleted) printf '%s\n' "$RESULT" | jq . >&2; exit 1 ;;
    *) sleep 2 ;;
  esac
done
Node.js example
const submitUrl = "https://api.wavespeed.ai/api/v3/kwaivgi/kling-v4.0-flash/reference-to-video";
const apiKey = process.env.WAVESPEED_API_KEY;
if (!apiKey) throw new Error('Set WAVESPEED_API_KEY');

async function requestJson(url, options = {}) {
  const response = await fetch(url, options);
  if (!response.ok) throw new Error(await response.text());
  return response.json();
}

// 1. Submit the prediction.
const body = await requestJson(submitUrl, {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${apiKey}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
        "prompt": "A cinematic shot of a city at sunset, soft golden light",
        "keep_original_sound": false,
        "duration": 5,
        "aspect_ratio": "auto"
}),
});
const task = body.data ?? body;
if (!task.id) throw new Error("Submission response did not contain a prediction id");
const resultUrl = `https://api.wavespeed.ai/api/v3/predictions/${task.id}/result`;

// 2. Poll until the prediction finishes.
while (true) {
  const resultBody = await requestJson(resultUrl, {
    headers: { "Authorization": `Bearer ${apiKey}` },
  });
  const result = resultBody.data ?? resultBody;
  if (result.status === "completed") {
    console.log(result.outputs);
    break;
  }
  if (["failed", "cancelled", "timeout", "deleted"].includes(result.status)) throw new Error(JSON.stringify(result));
  await new Promise(resolve => setTimeout(resolve, 2000));
}
Python example
import json
import os
import time
from urllib.request import Request, urlopen

api_key = os.environ["WAVESPEED_API_KEY"]
headers = {"Authorization": f"Bearer {api_key}", "Content-Type": "application/json"}
payload = {
    "prompt": "A cinematic shot of a city at sunset, soft golden light",
    "keep_original_sound": False,
    "duration": 5,
    "aspect_ratio": "auto"
}

def request_json(url, data=None):
    request = Request(url, data=data, headers=headers, method="POST" if data else "GET")
    with urlopen(request) as response:
        return json.load(response)

# 1. Submit the prediction.
body = request_json("https://api.wavespeed.ai/api/v3/kwaivgi/kling-v4.0-flash/reference-to-video", json.dumps(payload).encode())
task = body.get("data", body)
if not task.get("id"):
    raise RuntimeError("Submission response did not contain a prediction id")
result_url = f"https://api.wavespeed.ai/api/v3/predictions/{task['id']}/result"

# 2. Poll until the prediction finishes.
while True:
    result_body = request_json(result_url)
    result = result_body.get("data", result_body)
    status = result.get("status")
    if status == "completed":
        print(result.get("outputs", []))
        break
    if status in {"failed", "cancelled", "timeout", "deleted"}:
        raise RuntimeError(result)
    time.sleep(2)

Kling v4.0 Flash Reference To Video API — Frequently asked questions

What is the Kling v4.0 Flash Reference To Video API?

Kling v4.0 Flash Reference To Video is a Kuaishou model for reference-guided video generation, exposed as a REST API on WaveSpeedAI. Kling V4.0 Flash Reference-to-Video generates high-quality videos guided by reference images and videos, with synchronized audio and a focus on fast generation for character consistency, motion guidance, social content, marketing videos, and production workflows. Ready-to-use REST inference API. You can call it programmatically or try it from the playground above.

How do I call the Kling v4.0 Flash Reference To Video API?

POST your input parameters to the model's REST endpoint (shown in the API tab of this playground) with your WaveSpeedAI API key in the Authorization header. Submission returns a prediction ID. Poll the result endpoint starting around every 2 seconds, increase the interval for long-running tasks, and stop on any terminal status. The playground generates Python, JavaScript, and cURL examples for submitting requests and polling results. Full request/response shape is documented at https://wavespeed.ai/docs/docs-api/kwaivgi/kwaivgi-kling-v4.0-flash-reference-to-video.

How much does Kling v4.0 Flash Reference To Video cost per run or per second?

Kling v4.0 Flash Reference To Video starts at $0.094 per run or per second. That figure is the base price — the final charge scales with the parameters you set in the form (output size, length, count, references, or whatever knobs this model exposes), so a higher-quality or larger output costs more than a minimal one. The exact cost for your current input is shown live next to the Generate button before you submit, and the actual per-call charge is recorded on the prediction afterwards.

What inputs does Kling v4.0 Flash Reference To Video accept?

Key inputs: `prompt`, `images`, `aspect_ratio`, `duration`, `keep_original_sound`, `videos`. The full JSON schema (types, defaults, allowed values) is rendered above the Generate button and mirrored in the API reference at https://wavespeed.ai/docs/docs-api/kwaivgi/kwaivgi-kling-v4.0-flash-reference-to-video.

How do I get started with the Kling v4.0 Flash Reference To Video API?

Sign up for a free WaveSpeedAI account to claim starter credits, copy your API key from /accesskey, then call the endpoint shown in the API tab of the playground. The playground also auto-generates a code sample in Python, JavaScript, or cURL for the parameters you've set.

Can I use Kling v4.0 Flash Reference To Video outputs commercially?

Commercial usage rights depend on the model's license, set by its provider (Kuaishou). Check the provider's applicable terms and WaveSpeedAI's Terms of Service before commercial use.

llms.txt — kwaivgi/kling-v4.0-flash/reference-to-video for AI agents and LLMs