Bytedance Seedance 2.0 Fast Video Extend

Bytedance Seedance 2.0 Fast Video Extend

Playground

Seedance 2.0 Fast (Video-Extend) extends an input video with a new cinematic continuation generated from its last frame and a natural-language prompt — at the faster, cheaper Seedance 2.0 Fast tier. Ready-to-use REST API, best performance, no coldstarts, affordable pricing.

Features

Seedance 2.0 Fast Video-Extend is the faster, cheaper tier of Seedance 2.0 Video-Extend. It appends a new cinematic continuation to an existing video by generating a fresh segment from the input video’s last frame and a natural-language prompt, then concatenating original and new segment into a single output.

Key Features

• Seamless continuation — Generation starts from the input video’s last frame so the join is visually consistent.
• Optional target last frame — Provide last_image to steer the new segment toward a specific end frame.
• Director-level control — Camera movement, lighting, shadows, and character performance via prompts.
• Native audio synchronization — Audio from both the original video and the new segment are preserved in the final output.
• Faster, cheaper — ~17% cheaper than the standard Seedance 2.0 Video-Extend at every resolution.

Parameters

How to Use

1. Upload the input video. The new segment will be appended to it.
2. Write the prompt. Describe the continuation in cinematic detail.
3. (Optional) Upload a target last frame. The new segment will interpolate to this image.
4. Pick a duration and resolution.
5. Run. Receive the original video plus the new segment concatenated into one output.

Pricing

Billed per second of the new segment only. Resolution multipliers match Seedance 2.0 Fast image-to-video.

Examples (5s extension):

Notes

• Pricing is based on the new segment length only — the input video is not re-billed.
• Aspect ratio of the new segment matches the input video’s last frame automatically.
• Native audio generation is included for the new segment; the original video’s audio is preserved.

Related Models

• Seedance 2.0 Video-Extend — Standard tier of this model.
• Seedance 2.0 Fast Image-to-Video — Fast image-to-video generation.
• Seedance 2.0 Fast Video-Edit — Fast video-edit at 480p / 720p / 1080p / 4k.

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",
  "video": "https://interactive-examples.mdn.mozilla.net/media/cc0-videos/flower.mp4",
  "resolution": "720p",
  "duration": 5,
  "enable_web_search": false,
  "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/bytedance/seedance-2.0-fast/video-extend" \
  -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 "${PREDICTION_ID}" ]; then
  printf 'Submission response did not contain a prediction id
' >&2
  exit 1
fi
RESULT_URL=$(printf '%s' "${TASK}" | jq -r '.urls.get // empty')
if [ -z "${RESULT_URL}" ]; then RESULT_URL="https://api.wavespeed.ai/api/v3/predictions/${PREDICTION_ID}/result"; fi

# 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) printf '%s\n' "${RESULT}" | jq . >&2; exit 1 ;;
    created|processing) sleep 2 ;;
    *) printf 'Unexpected status: %s
' "${STATUS}" >&2; exit 1 ;;
  esac
done

Parameters

Task Submission Parameters

Request Parameters

Response Parameters

Result Request Parameters

Result Response Parameters