HappyHorse 1.0 Video Extend | AI Video Extension API

Alibaba Happy Horse 1.0 Video Extend

Alibaba Happy Horse 1.0 Video Extend continues an existing video clip with new AI-generated footage, seamlessly extending the scene from where the original ends. Upload a source video, describe how the video should continue, and the model generates a coherent continuation in 720p or 1080p.

Need to edit an existing clip instead of extending it? Try Alibaba Happy Horse 1.0 Video Edit.
Need to generate a new video from text? Try Alibaba Happy Horse 1.0 Text-to-Video.

Why Choose This?

Seamless video continuation Extend an existing clip with newly generated footage that picks up naturally from the original ending.
Prompt-guided scene progression Describe how the action, camera movement, atmosphere, or story should continue using natural language.
Cinematic motion Generate smooth, expressive motion while preserving the overall feel and flow of the source video.
Flexible resolution options Choose 720p for lower-cost iteration or 1080p for higher-quality final output.
Production-ready API Access the model through a REST inference API with no cold starts for scalable integration into creative workflows.

Parameters

Parameter	Required	Description
video	Yes	Source video to extend.
prompt	Yes	Text description of the desired continuation.
resolution	No	Output resolution: `720p` (default) or `1080p`.
duration	No	Total output duration in seconds. Range: `3–15`, default `5`.
seed	No	Random seed for reproducibility. Range: `0–2147483647`.

How to Use

Upload your source video — provide the clip you want to continue.
Write your prompt — describe how the scene, subject, camera, or atmosphere should progress after the original ending.
Choose resolution — use 720p for lower-cost iteration or 1080p for higher-quality results.
Set duration — choose the total output duration between 3 and 15 seconds.
Set a seed (optional) — use a fixed seed if you want more reproducible results.
Submit — generate and download the extended video.

Example Prompt

Continue the scene with a slow forward camera movement, the subject walking deeper into the alley, soft rain beginning to fall, stronger reflections on the ground, and a cinematic moody nighttime atmosphere

Pricing

Per 5 Seconds

Resolution	Cost
720p	$0.70
1080p	$1.40

Example Costs

Resolution	3s	5s	10s	15s
720p	$0.42	$0.70	$1.40	$2.10
1080p	$0.84	$1.40	$2.80	$4.20

Billing Rules

Base price: 720p costs $0.70 per 5 seconds
1080p surcharge: 1080p costs 2× the 720p rate
Total price formula:
total_price = 0.70 × (resolution == "1080p" ? 2 : 1) × duration / 5

Best Use Cases

Scene continuation — Extend cinematic clips with natural motion and coherent progression.
Storyboarding and concept work — Explore how a shot or sequence might continue without manual video production.
Ad creative development — Expand short promo clips into longer variations for campaigns and testing.
Social media content — Create longer edits from short source footage for platform-specific needs.
Atmospheric scene building — Continue motion, lighting, and mood from an existing clip into a richer sequence.
Creative prototyping — Quickly test alternate continuations before investing in full production.

Pro Tips

Use a source video with a clear ending frame for smoother continuation.
Be explicit about what should happen next, including subject action, camera motion, lighting, and atmosphere.
Keep prompts visually concrete, such as “camera slowly pushes in,” “the subject turns and walks away,” or “fog begins to roll in.”
Use 720p for quick testing, then switch to 1080p for final-quality output.
Reuse the same seed when you want more reproducible generations.
Start with shorter durations to validate continuity before generating longer clips.

Notes

Both video and prompt are required.
Ensure video URLs are publicly accessible.
Supported resolutions are 720p and 1080p.
Supported total output duration is 3–15 seconds.
Pricing scales linearly with duration.
1080p pricing is exactly 2× the 720p rate.

Related Models

Alibaba Happy Horse 1.0 Video Edit — Perform prompt-driven editing on existing videos.
Alibaba Happy Horse 1.0 Text-to-Video — Generate cinematic videos directly from natural-language prompts.
Alibaba Happy Horse 1.0 Image-to-Video — Animate a single reference image into a cinematic clip.

Happyhorse 1.0 Video Extend API — Quick start

Grab a WaveSpeedAI API key, then call POST https://api.wavespeed.ai/api/v3/alibaba/happyhorse-1.0/video-extend 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 Happyhorse 1.0 Video Extend below.

HTTP example

# Submit the prediction
curl -X POST "https://api.wavespeed.ai/api/v3/alibaba/happyhorse-1.0/video-extend" \
  -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",
    "resolution": "720p",
    "duration": 5,
    "seed": 0
}'

# 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("alibaba/happyhorse-1.0/video-extend", {
        "prompt": "A cinematic shot of a city at sunset, soft golden light",
        "video": "https://example.com/your-input.mp4",
        "resolution": "720p",
        "duration": 5,
        "seed": 0
});

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

Python example

# pip install wavespeed
import wavespeed

output = wavespeed.run(
    "alibaba/happyhorse-1.0/video-extend",
    {
    "prompt": "A cinematic shot of a city at sunset, soft golden light",
    "video": "https://example.com/your-input.mp4",
    "resolution": "720p",
    "duration": 5,
    "seed": 0
}
)

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

Happyhorse 1.0 Video Extend API — Frequently asked questions

What is the Happyhorse 1.0 Video Extend API?

Happyhorse 1.0 Video Extend is a Alibaba model for video extension, exposed as a REST API on WaveSpeedAI. Alibaba Happy Horse 1.0 (Video Extend) extends existing videos with seamless AI-generated continuation, supporting 720p/1080p output. Ready-to-use REST API, best performance, no coldstarts, affordable pricing. You can call it programmatically or try it from the playground above.

How do I call the Happyhorse 1.0 Video Extend 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/alibaba/alibaba-happyhorse-1.0-video-extend.

How much does Happyhorse 1.0 Video Extend cost per run?

Happyhorse 1.0 Video Extend starts at $0.70 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 Happyhorse 1.0 Video Extend accept?

Key inputs: `prompt`, `video`, `resolution`, `duration`, `seed`. 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/alibaba/alibaba-happyhorse-1.0-video-extend.

How do I get started with the Happyhorse 1.0 Video Extend API?

Sign up for a free WaveSpeedAI account to claim starter credits, copy your API key from /accesskey, then call the endpoint shown in the API tab of the playground. The playground also auto-generates a code sample in Python, JavaScript, or cURL for the parameters you've set.

Can I use Happyhorse 1.0 Video Extend outputs commercially?

Commercial usage rights depend on the model's license, set by its provider (Alibaba). The license summary appears on the model card above; see WaveSpeedAI's Terms of Service for platform-level conditions.

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