Black Forest Labs Flux 3 Start End To Video Draft API Documentation

Black Forest Labs Flux 3 Start End To Video Draft API Documentation

Playground

FLUX 3 Start-End-to-Video Draft quickly generates a transition between required start and end images, with prompt-guided motion, optional synchronized audio, and flexible 5-20 second duration for rapid keyframe iteration.

Features

FLUX 3 Draft Start-End-to-Video quickly generates a transition between a required starting image and a required ending image. Use it to test action, transformation, camera movement, pacing, and visual style between two keyframes before moving to a final-quality workflow.

Why Choose This?

• Start-and-end-frame control
  Generate a video transition from a defined first frame to a defined final frame.

• Fast transition preview
  Quickly test movement, transformation, camera paths, environment changes, and pacing.

• Prompt-guided motion
  Describe how the subject, scene, lighting, and camera should evolve between the two keyframes.

• Optional synchronized audio
  Generate matching audio for early sound, ambience, effects, music, or dialogue tests.

• Flexible duration
  Choose a draft video duration from 5 to 20 seconds.

• Multiple aspect ratios
  Supports landscape, portrait, square, and cinematic formats.

Parameters

How to Use

1. Upload the start image — Provide the image that should appear at the beginning of the transition.
2. Upload the end image — Provide the image that should appear at the end of the transition.
3. Write the prompt — Describe the movement, transformation, camera path, timing, and style between the two keyframes.
4. Choose aspect ratio — Select the output format that matches your target use case.
5. Set duration — Choose a draft duration from 5 to 20 seconds.
6. Configure audio optional — Enable generate_audio when you want to test ambience, effects, music, or dialogue.
7. Submit — Generate the draft transition video.

Pricing

Pricing is based on billed video duration.

Billed duration is rounded up to the next whole second and capped at 20 seconds. The API accepts durations from 5 to 20 seconds. Audio generation does not add a separate charge.

Example Costs

Best Use Cases

• Product reveals — Transition from a hidden or simple product setup to a polished reveal.
• Before-and-after concepts — Show visual transformation between two defined states.
• Character transformations — Animate outfit, pose, style, or environment changes between keyframes.
• Logo and brand transitions — Create fast previews for motion branding and visual identity work.
• Story keyframes — Connect two planned story moments with controlled motion and pacing.
• Social media transitions — Generate short transition clips for vertical, square, or widescreen content.

Pro Tips

• Use visually compatible start and end images when you want a smoother transition.
• Describe the path from the start image to the end image instead of listing unrelated scenes.
• Explain what moves, transforms, appears, disappears, or changes between the keyframes.
• Add camera directions such as dolly-in, pull-back, orbit, tracking shot, or crane movement.
• Keep the first test simple, then refine the prompt after reviewing the draft output.
• Use shorter durations for quick iteration and longer durations when the transition needs more time to unfold.

Related Models

• FLUX 3 Draft Start-End-to-Video — Generate a draft transition between a start image and an end image.
• FLUX 3 Draft Image-to-Video — Animate a reference image into a draft video.
• FLUX 3 Draft Video Extend — Extend an existing video with a new draft continuation.
• FLUX 3 Draft Text-to-Video — Generate draft videos directly from text prompts.

Authentication

For authentication details, please refer to the Authentication Guide.

API Endpoints

Submit Task & Query Result

set -euo pipefail

export WAVESPEED_API_KEY="your-api-key"

REQUEST_BODY=$(cat <<'JSON'
{
  "prompt": "A cinematic ocean wave at sunrise, highly detailed",
  "start_image": "https://interactive-examples.mdn.mozilla.net/media/cc0-images/painted-hand-298-332.jpg",
  "end_image": "https://interactive-examples.mdn.mozilla.net/media/cc0-images/painted-hand-298-332.jpg",
  "aspect_ratio": "21:9",
  "duration": 5,
  "generate_audio": true
}
JSON
)

# 1. Submit the prediction.
SUBMIT_RESPONSE=$(curl --silent --show-error --fail-with-body \
  -X POST "https://api.wavespeed.ai/api/v3/black-forest-labs/flux-3/start-end-to-video-draft" \
  -H "Authorization: Bearer ${WAVESPEED_API_KEY}" \
  -H "Content-Type: application/json" \
  -d "${REQUEST_BODY}")

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

  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

Parameters

Task Submission Parameters

Request Parameters

Response Parameters

Result Request Parameters

Result Response Parameters