> ## Documentation Index
> Fetch the complete documentation index at: https://apixo.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Seedance 1.5 Pro Video-Extend
> Extend short source clips into longer videos with natural continuation, stable aesthetics, and production-ready API delivery
## Overview
Seedance 1.5 Pro Video-Extend turns short source clips into longer videos with natural motion continuation, stable aesthetics, and a clean final output. APIXO analyzes the source video and applies its video extension workflow to produce a longer continuation through the standard async task API.
It is a strong fit for extending ad creatives, short-drama shots, talking-head clips, and other short-form scenes where you want the next moment of the same shot instead of a brand-new composition.
| Capability | Value |
| --------------- | ------------------------------------------------------------------------------ |
| Model ID | `seedance-1-5-pro-extend` |
| Required mode | `video-extend` |
| Source input | Exactly 1 public video URL in `video_urls` |
| Prompt length | 3-2500 characters |
| Resolutions | `480p`, `720p`, `1080p` |
| Duration | 4-12 seconds |
| Audio | Required `sound` toggle |
| Aspect handling | Adaptive continuation based on the source clip; no public `aspect_ratio` field |
| Reproducibility | Optional `seed` support |
| Output | Final stitched video URL in `resultJson.resultUrls` |
## Endpoint and authentication
Base URL:
```text theme={null}
https://api.apixo.ai/api/v1
```
| Method | Endpoint | Purpose |
| ------ | ----------------------------------------------------- | ------------------------------------------------------ |
| `POST` | `/generateTask/seedance-1-5-pro-extend` | Submit a video extend task |
| `GET` | `/statusTask/seedance-1-5-pro-extend?taskId={taskId}` | Poll task status and retrieve the final stitched video |
All requests require your APIXO API key:
```http theme={null}
Authorization: Bearer YOUR_API_KEY
```
Submit requests also require:
```http theme={null}
Content-Type: application/json
```
## Copy-paste async quickstart
This minimal request extends a short source clip and returns a new `taskId`.
```bash theme={null}
curl -X POST "https://api.apixo.ai/api/v1/generateTask/seedance-1-5-pro-extend" \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"request_type": "async",
"input": {
"mode": "video-extend",
"prompt": "keep the same framing, smile at the camera, then ride away naturally",
"resolution": "480p",
"duration": 4,
"sound": false,
"camera_fixed": true,
"video_urls": [
"https://example.com/source.mp4"
]
}
}'
```
Successful response:
```json theme={null}
{
"code": 200,
"message": "success",
"data": {
"taskId": "task_12345678"
}
}
```
Save the `taskId`; you need it to poll for the final result.
## Poll for result
```bash theme={null}
curl -X GET "https://api.apixo.ai/api/v1/statusTask/seedance-1-5-pro-extend?taskId=task_12345678" \
-H "Authorization: Bearer YOUR_API_KEY"
```
Processing response:
```json theme={null}
{
"code": 200,
"message": "success",
"data": {
"taskId": "task_12345678",
"state": "processing",
"createTime": 1767965610929
}
}
```
Success response:
```json theme={null}
{
"code": 200,
"message": "success",
"data": {
"taskId": "task_12345678",
"state": "success",
"resultJson": "{\"resultUrls\":[\"https://file.apixo.ai/xxx.mp4\"]}",
"createTime": 1767965610929,
"completeTime": 1767965695412,
"costTime": 84483
}
}
```
Failed response:
```json theme={null}
{
"code": 200,
"message": "success",
"data": {
"taskId": "task_12345678",
"state": "failed",
"failCode": "API_SERVICE_UNAVAILABLE",
"failMsg": "Video extend processing is temporarily unavailable",
"createTime": 1767965610929,
"completeTime": 1767965620132,
"costTime": 9203
}
}
```
Parse `resultJson` after `state` becomes `success`:
```javascript theme={null}
const payload = JSON.parse(data.resultJson);
const videoUrls = payload.resultUrls;
```
## Request body
```json theme={null}
{
"request_type": "async",
"input": {
"mode": "video-extend",
"prompt": "continue the same shot with a gentle smile and then a smooth ride-away",
"video_urls": [
"https://example.com/source.mp4"
],
"resolution": "720p",
"duration": 8,
"sound": true,
"camera_fixed": true,
"seed": 123456,
"watermark": false
}
}
```
## Parameters
Result delivery mode. Use `async` for polling with `statusTask`, or `callback` for webhook delivery.
Required when `request_type` is `callback`. Must be a public HTTPS URL that can receive the final task payload. See [Webhooks](/api-reference/webhooks).
Seedance 1.5 Pro Video-Extend input parameters.
Required public mode for this model. Supported values: `video-extend`.
Continuation prompt for the next moment of the same shot. Supports 3-2500 characters after trimming.
Source clip URLs. Provide exactly 1 public video URL. APIXO analyzes the tail of this clip before generating the continuation.
Output resolution for the continuation workflow. Supported values: `480p`, `720p`, `1080p`.
Requested extension duration in seconds. Accepts integer values from `4` to `12`; numeric strings are also accepted by the backend.
Whether to generate audio with the extended segment. Use `true` for generated sound, or `false` for a silent result.
Whether to keep the camera behavior stable during continuation. Supported values: `true`, `false`. If omitted, the backend defaults this field to `true`.
Optional random seed for more reproducible continuation results. Supported range: `0` to `2147483647`.
Whether to keep the upstream watermark when the selected route supports it. Supported values: `true`, `false`.
Legacy `fixed_lens` is still accepted for compatibility, but new integrations should use `camera_fixed`.
## Response format
### Submit task response
`POST /generateTask/seedance-1-5-pro-extend` returns a task ID when the task is accepted:
API status code. `200` means the task was accepted.
Human-readable status message.
Unique task identifier used with the status endpoint.
### Status response fields
Unique task identifier.
Current task state: `processing`, `success`, or `failed`.
JSON string containing the final stitched video URLs. Present when `state` is `success`.
Machine-readable failure code. Present when `state` is `failed`.
Human-readable failure message. Present when `state` is `failed`.
Task creation timestamp in Unix milliseconds.
Task completion timestamp in Unix milliseconds. Present after completion.
Processing duration in milliseconds. Present after completion when available.
## Webhook callback mode
Use callback mode when your backend should receive the final result automatically instead of polling.
```bash theme={null}
curl -X POST "https://api.apixo.ai/api/v1/generateTask/seedance-1-5-pro-extend" \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"request_type": "callback",
"callback_url": "https://your-server.com/webhooks/apixo",
"input": {
"mode": "video-extend",
"prompt": "continue the same scene with a smooth smile, then leave the frame naturally",
"video_urls": [
"https://example.com/source.mp4"
],
"resolution": "720p",
"duration": 8,
"sound": true,
"camera_fixed": true,
"seed": 123456
}
}'
```
The callback payload uses the same unified response shape as the status endpoint when the task reaches a final state. See [Webhooks](/api-reference/webhooks) for delivery requirements and retry behavior.
## Billing
Seedance 1.5 Pro Video-Extend uses the same per-second pricing tiers as Seedance 1.5 Pro, so cost stays predictable even though the workflow includes continuation analysis and final stitching.
| Resolution | `sound` | Price |
| ---------- | ------- | ----------------- |
| `480p` | `false` | `$0.012 / second` |
| `480p` | `true` | `$0.024 / second` |
| `720p` | `false` | `$0.024 / second` |
| `720p` | `true` | `$0.048 / second` |
| `1080p` | `false` | `$0.052 / second` |
| `1080p` | `true` | `$0.104 / second` |
Total cost is the per-second price multiplied by the requested duration. For example, `720p` with `sound: false` for 8 seconds costs `$0.192`.
For current route and market comparison pricing, see [Pricing](https://apixo.ai/pricing).
## Latency and polling
This workflow includes tail analysis and final stitching in addition to upstream generation, so it may take slightly longer than direct text-to-video or image-to-video generation. In return, you get a cleaner continuation workflow and a single ready-to-use output URL.
| Requested duration | Recommended first poll | Poll interval |
| ------------------ | ----------------------- | ------------- |
| `4` seconds | 45s after task creation | 5s-10s |
| `8` seconds | 60s after task creation | 5s-10s |
| `12` seconds | 90s after task creation | 5s-10s |
For production workloads, use callback mode to avoid frequent polling while the continuation and merge steps complete.
Rate limits and concurrency can vary by account, API key, and route. If you receive `429`, slow down requests and retry with backoff. For account-level details, see [System APIs](/api-reference/system).
## Errors and troubleshooting
### HTTP errors
| Code | Meaning | What to do |
| ----- | --------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------- |
| `400` | Invalid request body, missing required field, unsupported resolution, invalid duration, or malformed source URL array | Fix the request before retrying |
| `401` | Missing or invalid API key | Check the `Authorization` header |
| `402` | Insufficient balance or quota | Add balance or switch account/key |
| `403` | Key or route cannot access the model | Check permissions and route strategy |
| `429` | Rate limit or concurrency limit reached | Retry with exponential backoff |
| `500` | Server error or internal processing error | Retry with backoff; contact support if it repeats |
| `502` | Upstream error | Retry with backoff |
| `504` | Upstream timeout | Retry or use callback mode for long-running jobs |
### Task failure codes
| Fail code | Meaning | What to do |
| ------------------------- | -------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------- |
| `MISSING_REQUIRED_PARAM` | A required field such as `mode`, `prompt`, `video_urls`, `resolution`, `duration`, or `sound` is missing | Fix the request before retrying |
| `INVALID_PARAMETER` | One or more fields use an unsupported value or type | Check `mode`, `resolution`, `duration`, `sound`, `camera_fixed`, `seed`, and `watermark` |
| `API_SERVICE_UNAVAILABLE` | Tail analysis, merge processing, or upstream continuation is temporarily unavailable | Retry later |
| `SensitiveContent` | The continuation prompt or generated content violated upstream policy | Change the prompt and retry |
| `RateLimited` | The upstream route rate limited the task | Retry later with backoff |
| `Timeout` | The workflow did not finish in time | Retry, simplify the prompt, or use callback mode |
| `Unknown error` | The failure did not match a known public mapping | Retry or contact support with the `taskId` |
### Common validation fixes
| Symptom | Fix |
| ------------------------ | ------------------------------------------------ |
| `mode` is rejected | Set `input.mode` to `video-extend` |
| `video_urls` is rejected | Provide exactly 1 public video URL |
| `resolution` is rejected | Use `480p`, `720p`, or `1080p` |
| `duration` is rejected | Send an integer from `4` to `12` |
| `sound` is rejected | Send a boolean: `true` or `false` |
| Prompt length error | Keep the trimmed prompt within 3-2500 characters |
See [Error Codes](/api-reference/errors) for the full error reference.
## Related links
* [Seedance 1.5 Pro](/models/video/seedance-1-5-pro)
* [Generation API Overview](/models)
* [Generate Task](/api-reference/generate-task)
* [Status Task](/api-reference/status-task)
* [Webhooks](/api-reference/webhooks)
* [Error Codes](/api-reference/errors)
* [Parameter Specification](/api-reference/parameters)
* [Routing Strategies](/concepts/routing-strategies)
* [Pricing](https://apixo.ai/pricing)