Seedance V1.5 Pro Video Extend Fast | AI Video Extension API

Seedance V1.5 Pro Fast — Video Extend

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.

Why it stands out

Smooth continuation that follows the original clip’s motion rhythm and visual style
Prompt-guided extension to steer actions, mood, and camera behavior
Resolution control with a simple cost multiplier (720p vs 1080p)
Optional audio generation with transparent pricing impact

Key Capabilities

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).

Parameters

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).

Prompt Tips

Write prompts like a continuation director’s note:

Action next: what happens after the input ends
Motion intensity: subtle / smooth / dynamic / dramatic
Camera behavior: fixed / slow pan / gentle zoom (if you care, say it)
Consistency constraints: “keep the same character, outfit, lighting, framing”

Example prompts:

Continue the scene with the woman giving a wink to the camera, keep the same lighting and framing, subtle motion, natural facial expression.
Extend with a slow zoom out to reveal more of the environment while keeping the subject centered and the mood unchanged.

Pricing

Reference pricing (generate_audio = true)

Resolution	Price per second	Example (5s)	Example (10s)
720p	$0.04	$0.20	$0.40
1080p	$0.06	$0.30	$0.60

Reference pricing (generate_audio = false)

Resolution	Price per second	Example (5s)	Example (10s)
720p	$0.02	$0.10	$0.20
1080p	$0.03	$0.15	$0.30

Best Practices

Use clean input videos (clear subject, stable exposure, minimal compression artifacts).
Keep prompts specific but short, and state what must stay the same.
Start with 5s to validate motion and framing before extending longer.
Use 720p for fast preview iterations, then switch to 1080p for final.
Set a fixed seed when you want consistent reruns while refining the prompt.

Use Cases

Ad creative extension (turn short shots into longer deliverables)
Social content variations (longer cuts from a base clip)
Storytelling continuity (extend key moments with controlled motion)
Marketing edits (extend hero scenes with stable aesthetics)

Notes

The input video must be accessible to the runtime (public URL or valid uploaded reference).
If motion drifts or changes too much, add stronger constraints: “keep face unchanged”, “keep camera fixed”, “same outfit and lighting”.
Capability and allowed duration values can vary by deployment; rely on the endpoint’s UI/validator for the exact supported options.

Related Models

Seedance V1.5 Pro Video Extend — Standard video extension option for stable, production-oriented continuation.
Seedance V1.5 Pro (Text-to-Video Fast) — Generate new videos from text prompts with fast turnaround.
Seedance V1.5 Pro (Image-to-Video Fast) — Animate a still image into video with fast generation speed.

Seedance v1.5 Pro Video Extend Fast API — Quick start

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; poll the prediction endpoint until status flips to completed, then read the output URL from data.outputs[0]. Examples for Seedance v1.5 Pro Video Extend Fast below.

HTTP example

# Submit the prediction
curl -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 '{
    "prompt": "A cinematic shot of a city at sunset, soft golden light",
    "video": "https://example.com/your-input.mp4",
    "duration": 5,
    "resolution": "720p",
    "generate_audio": true,
    "camera_fixed": false,
    "seed": -1
}'

# Response includes a prediction id. Poll for the result:
curl -X GET "https://api.wavespeed.ai/api/v3/predictions/{request_id}/result" \
  -H "Authorization: Bearer $WAVESPEED_API_KEY"

# When status is "completed", read the output from data.outputs[0].

Node.js example

// npm install wavespeed
const WaveSpeed = require('wavespeed');

const client = new WaveSpeed(); // reads WAVESPEED_API_KEY from env

const result = await client.run("bytedance/seedance-v1.5-pro/video-extend-fast", {
        "prompt": "A cinematic shot of a city at sunset, soft golden light",
        "video": "https://example.com/your-input.mp4",
        "duration": 5,
        "resolution": "720p",
        "generate_audio": true,
        "camera_fixed": false,
        "seed": -1
});

console.log(result.outputs[0]); // → URL of the generated output

Python example

# pip install wavespeed
import wavespeed

output = wavespeed.run(
    "bytedance/seedance-v1.5-pro/video-extend-fast",
    {
    "prompt": "A cinematic shot of a city at sunset, soft golden light",
    "video": "https://example.com/your-input.mp4",
    "duration": 5,
    "resolution": "720p",
    "generate_audio": true,
    "camera_fixed": false,
    "seed": -1
}
)

print(output["outputs"][0])  # → URL of the generated output

Seedance v1.5 Pro Video Extend Fast API — Frequently asked questions

What is the Seedance v1.5 Pro Video Extend Fast API?

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.

How do I call the Seedance v1.5 Pro Video Extend Fast 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 prediction endpoint until status flips to "completed", then read the output URL from the result. The playground generates a ready-to-paste code sample in Python, JavaScript, or cURL for whatever inputs you've set. Full request/response shape is documented at https://wavespeed.ai/docs/docs-api/bytedance/bytedance-seedance-v1.5-pro-video-extend-fast.

How much does Seedance v1.5 Pro Video Extend Fast cost per run?

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.

What inputs does Seedance v1.5 Pro Video Extend Fast accept?

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.

How long does Seedance v1.5 Pro Video Extend Fast take to generate?

Average end-to-end generation time on WaveSpeedAI is around 653 seconds per request — measured across recent runs. Queue time scales with global demand; live status is visible in the prediction record.

Can I use Seedance v1.5 Pro Video Extend Fast outputs commercially?

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.

ExamplesView all

Related Models

README

Seedance V1.5 Pro Fast — Video Extend

Why it stands out

Key Capabilities

Parameters

Prompt Tips

Pricing

Reference pricing (generate_audio = true)

Reference pricing (generate_audio = false)

Best Practices

Use Cases

Notes

Related Models

Seedance v1.5 Pro Video Extend Fast API — Quick start

Seedance v1.5 Pro Video Extend Fast API — Frequently asked questions