> ## Documentation Index
> Fetch the complete documentation index at: https://docs.jiekou.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Veo 3.1 Fast Video Extension

Use the Google Veo 3.1 Fast model to extend an input video by 7 seconds. Supports 720p and 1080p resolutions, as well as 16:9 and 9:16 aspect ratios. Input video requirements: MP4 format, 24fps, and 1-30 seconds in duration.

<Tip>
  This is an **asynchronous** API and only returns the task\_id of the async task. You should use this task\_id to request the [Get Task Result API](/en/docs/models/reference-get-async-task-result) to retrieve the generated result.
</Tip>

## Request Headers

<ParamField header="Content-Type" type="string" required={true}>
  Enum value: `application/json`
</ParamField>

<ParamField header="Authorization" type="string" required={true}>
  Bearer authentication format: Bearer \{\{API Key}}.
</ParamField>

## Request Body

<ParamField body="seed" type="integer">
  Random seed used to reproduce generation results.

  Value range: \[0, 4294967295]
</ParamField>

<ParamField body="video" type="string" required={true}>
  Input video. Supports video URLs or Base64-encoded data. Video requirements: MP4 format, 24fps, 1-30 seconds in duration, 720p/1080p resolution, and a 16:9 or 9:16 aspect ratio.
</ParamField>

<ParamField body="prompt" type="string" required={true}>
  Text prompt describing the content for video extension.
</ParamField>

<ParamField body="resolution" type="string" default="720p">
  Output video resolution.

  Available values: `720p`, `1080p`
</ParamField>

<ParamField body="aspect_ratio" type="string" default="16:9">
  Output video aspect ratio.

  Available values: `16:9`, `9:16`
</ParamField>

<ParamField body="sample_count" type="integer" default={1}>
  Number of generated video samples (1-4).

  Value range: \[1, 4]
</ParamField>

<ParamField body="generate_audio" type="boolean" default={false}>
  Whether to also generate audio. Note: video extension itself does not support audio generation; this parameter is only used to distinguish SKU billing.
</ParamField>

<ParamField body="negative_prompt" type="string">
  Describes what should be avoided in the generated video.
</ParamField>

<ParamField body="person_generation" type="string" default="allow_adult">
  Whether to allow generating adult people. allow\_adult: allow generating adults; dont\_allow: do not allow generating people.

  Available values: `allow_adult`, `dont_allow`
</ParamField>

## Response Information

<ResponseField name="task_id" type="string" required={false}>
  Use the task\_id to request the [Get Task Result API](/en/docs/models/reference-get-async-task-result) to retrieve the generated output.
</ResponseField>