Seedance 1.5 Pro Fast Video Extend turns short shots into longer clips with natural motion continuation and strong temporal consistency. Supports 4–12 s extensions, 720p/1080p output with built-in upscaling, and seed-reproducible results for shot matching. Ideal for ads, trailers, and short-drama beats. Production-ready REST API with fast response, no cold starts, and affordable pricing.
就緒
$0.2每次運行·~50 / $10
The woman is smiling at the camera, and the sun is shining on her hair
The woman is giving a wink to the camera
Santa Claus stands up and walks away
The woman is smiling at the camera, and the sun is shining on her hair
Seedance V1.5 Pro Fast (Video Extend) extends an existing video into a longer clip while maintaining motion continuity, subject consistency, and scene coherence. Use a guiding prompt to control what happens next, choose duration and resolution, and optionally generate audio for the extended segment.
Natural motion continuation Extends movement in a way that feels consistent with the input clip.
Scene coherence preservation Keeps lighting, composition, and identity cues stable across the extension.
Prompt-guided direction Describe what should happen next without rebuilding the scene from scratch.
Optional audio generation Enable or disable audio generation (pricing differs).
| Parameter | Description |
|---|---|
| video* | Input video (public URL or uploaded file reference, depending on client). |
| prompt* | Describe what should happen next and what must remain consistent. |
| duration | Output duration in seconds, up to 12s (allowed values depend on the endpoint configuration). |
| resolution | Output resolution: 720p or 1080p. |
| generate_audio | Whether to generate audio for the output video (true/false). |
| camera_fixed | Whether to fix the camera position (true/false). |
| seed | Random seed (-1 for random; set a fixed integer for reproducible results). |
Write prompts like a continuation director’s note:
Example prompts:
| Resolution | Price per second | Example (5s) | Example (10s) |
|---|---|---|---|
| 720p | $0.04 | $0.20 | $0.40 |
| 1080p | $0.06 | $0.30 | $0.60 |
| Resolution | Price per second | Example (5s) | Example (10s) |
|---|---|---|---|
| 720p | $0.02 | $0.10 | $0.20 |
| 1080p | $0.03 | $0.15 | $0.30 |
Grab a WaveSpeedAI API key, then call POST https://api.wavespeed.ai/api/v3/bytedance/seedance-v1.5-pro/video-extend-fast with your input as JSON. The endpoint returns a prediction id. Start polling the result endpoint around every 2 seconds, increase the interval for long-running tasks, and stop on any terminal status. On completed, read output values from data.outputs. Examples for Seedance v1.5 Pro Video Extend Fast below.
set -euo pipefail
: "${WAVESPEED_API_KEY:?Set WAVESPEED_API_KEY}"
REQUEST_BODY=$(cat <<'JSON'
{
"prompt": "A cinematic shot of a city at sunset, soft golden light",
"video": "https://interactive-examples.mdn.mozilla.net/media/cc0-videos/flower.mp4",
"duration": 5,
"resolution": "720p",
"generate_audio": true,
"camera_fixed": false,
"seed": -1
}
JSON
)
# 1. Submit the prediction.
SUBMIT_RESPONSE=$(curl --silent --show-error --fail-with-body \
-X POST "https://api.wavespeed.ai/api/v3/bytedance/seedance-v1.5-pro/video-extend-fast" \
-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=$(printf '%s' "$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' "$RESPONSE" | jq 'if has("data") then .data else . end')
STATUS=$(printf '%s' "$RESULT" | jq -r '.status')
case "$STATUS" in
completed) printf '%s\n' "$RESULT" | jq '.outputs'; break ;;
failed|cancelled|timeout) printf '%s\n' "$RESULT" | jq . >&2; exit 1 ;;
created|processing) sleep 2 ;;
*) printf 'Unexpected status: %s
' "$STATUS" >&2; exit 1 ;;
esac
doneconst submitUrl = "https://api.wavespeed.ai/api/v3/bytedance/seedance-v1.5-pro/video-extend-fast";
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 ${apiKey}`,
"Content-Type": "application/json",
},
body: JSON.stringify({
"prompt": "A cinematic shot of a city at sunset, soft golden light",
"video": "https://interactive-examples.mdn.mozilla.net/media/cc0-videos/flower.mp4",
"duration": 5,
"resolution": "720p",
"generate_audio": true,
"camera_fixed": false,
"seed": -1
}),
});
const task = body.data ?? body;
if (!task.id) throw new Error("Submission response did not contain a prediction id");
const resultUrl = task.urls?.get ||
`https://api.wavespeed.ai/api/v3/predictions/${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"].includes(result.status)) throw new Error(JSON.stringify(result));
if (!["created", "processing"].includes(result.status)) throw new Error("Unexpected status: " + result.status);
await new Promise(resolve => setTimeout(resolve, 2000));
}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",
"video": "https://interactive-examples.mdn.mozilla.net/media/cc0-videos/flower.mp4",
"duration": 5,
"resolution": "720p",
"generate_audio": True,
"camera_fixed": False,
"seed": -1
}
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/bytedance/seedance-v1.5-pro/video-extend-fast", 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 = task.get("urls", {}).get("get") or 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"}:
raise RuntimeError(result)
if status not in {"created", "processing"}:
raise RuntimeError(f"Unexpected status: {status}")
time.sleep(2)Seedance v1.5 Pro Video Extend Fast is a ByteDance model for video extension, exposed as a REST API on WaveSpeedAI. Seedance 1.5 Pro Fast Video Extend turns short shots into longer clips with natural motion continuation and strong temporal consistency. Supports 4–12 s extensions, 720p/1080p output with built-in upscaling, and seed-reproducible results for shot matching. Ideal for ads, trailers, and short-drama beats. Production-ready REST API with fast response, no cold starts, and affordable pricing. You can call it programmatically or try it from the playground above.
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 production-oriented Python, JavaScript, and cURL examples with timeouts, transient-error handling, and safe GET retries. Full request/response shape is documented at https://wavespeed.ai/docs/docs-api/bytedance/bytedance-seedance-v1.5-pro-video-extend-fast.
Seedance v1.5 Pro Video Extend Fast starts at $0.20 per run. 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.
Key inputs: `prompt`, `video`, `resolution`, `duration`, `seed`, `camera_fixed`. 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/bytedance/bytedance-seedance-v1.5-pro-video-extend-fast.
Median end-to-end generation time on WaveSpeedAI is around 260 seconds per request, based on recent successful runs. Queue time varies with global demand; live status is visible in the prediction record.
Commercial usage rights depend on the model's license, set by its provider (ByteDance). The license summary appears on the model card above; see WaveSpeedAI's Terms of Service for platform-level conditions.