Seedance 1.5 Pro Video Extend Fast | Video Extend for Longer Clips (720p/1080p)

ByteDance 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.

ExamplesView all

README