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

# Audio Speed Changer

> Processes an audio file to change its playback speed based on a speed factor.

Change the speed of your audio files without affecting quality.

**Audio Speed Changer** allows you to easily speed up or slow down any audio file — perfect for creating remixes, practicing music, or adjusting spoken content.

* Speed up or slow down audio effortlessly
* Supports multiple formats like MP3, WAV, FLAC, and more
* Fast processing with high-quality output

***

## Endpoint

```http theme={null}
POST /audio_speed_changer
```

Use this endpoint to adjust the speed of an audio file.

***

## Sample Output

Listen to the speed-changed audio:
<audio controls="1" controlslist="nodownload nofullscreen noremoteplayback" src="https://lalals.s3.amazonaws.com/FileConversions/b0ac9d46-64d7-4843-af48-a0b6effe3666.wav">Your browser does not support audio playback.</audio>

***

## Try it Yourself

Visit the [Audio Speed Changer Endpoint Explorer](/api-documentation/endpoint/audio_speed_changer) to upload audio files and adjust their playback speed.

> ⏩ Try different speed factors like 1.5x or 0.75x to test quality!

***

## Request Parameters

| Parameter             | Type   | Required | Description                                                                               |
| --------------------- | ------ | -------- | ----------------------------------------------------------------------------------------- |
| `audio_path`          | String | Yes      | The S3 path of the input audio file                                                       |
| `conversion_id`       | String | Yes      | Unique identifier for this conversion request                                             |
| `speed_change_factor` | Number | Yes      | Factor to change speed (e.g., 2.0 = double speed, 0.5 = half speed) (min: 0.25, max: 4.0) |
| `output_extension`    | String | Yes      | Desired output format (`mp3`, `wav`, `flac`, `ogg`, `aac`, `webm`)                        |
| `webhook_url`         | String | Optional | URL to receive callback notification when processing completes                            |
| `user_id`             | String | Optional | User ID for tracking (from authentication token)                                          |

> **content-type:** multipart/form-data

***

## Sample Request

### Python

```python theme={null}
import requests

url = "https://api.musicgpt.com/api/public/v1/audio_speed_changer"
headers = {"Authorization": "<API_KEY>"}

# Option 1: Use audio URL
payload = {
    "audio_url": "https://example.com/input_audio.mp3",
    "speed_change_factor": 1.5,
    "output_extension": "mp3"
}
response = requests.post(url, headers=headers, data=payload)
print(response.json())

# Option 2: Upload local audio file
payload = {
    "speed_change_factor": 1.25,
    "output_extension": "wav"
}
with open("input_audio.mp3", "rb") as f:
    files = {"audio_file": f}
    response = requests.post(url, headers=headers, data=payload, files=files)
print(response.json())
```

***

## Sample Response

### Success (200 OK)

```json theme={null}
{
  "success":true,
  "task_id":"b0ac9d46-64d7-4843-af48-a0b6effe3666",
  "conversion_id":"fe19945b-d466-4183-b559-5d264bddd492",
  "eta":66,
  "credit_estimate":25.0,
  "message":"Message published to queue",
  "status":"IN_QUEUE"
}
```

***

## Webhook Response

When transcription completes, your webhook will receive:

```json theme={null}
{
  "success": true, 
  "conversion_type": "Audio Speed Changer", 
  "task_id": "b0ac9d46-64d7-4843-af48-a0b6effe3666", 
  "conversion_id": "fe19945b-d466-4183-b559-5d264bddd492", 
  "output_file": "https://lalals.s3.amazonaws.com/FileConversions/b0ac9d46-64d7-4843-af48-a0b6effe3666.wav", 
  "message": "Audio speed changer completed"
}
```

> 📂 The `conversion_path` field contains the direct link to download the speed-modified audio.

***

## Payload and Request Formation


## OpenAPI

````yaml POST /v1/audio_speed_changer
openapi: 3.1.0
info:
  title: Musicgpt API
  version: 1.0.0
  description: API for retrieving conversion details by ID.
servers:
  - url: https://api.musicgpt.com/api/public
    description: Production server
security: []
paths:
  /v1/audio_speed_changer:
    post:
      summary: Change the speed of an audio file
      description: >-
        Processes an audio file to change its playback speed based on a speed
        factor.
      requestBody:
        required: true
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                audio_url:
                  type: string
                  description: URL of the input audio to change speed.
                  example: https://example.com/input_audio.mp3
                audio_file:
                  type: string
                  format: binary
                  description: Audio file to upload and process directly.
                speed_change_factor:
                  type: number
                  description: 'Factor to change the audio speed (min: 0.25, max: 4.0)'
                  minimum: 0.25
                  maximum: 4
                  example: 1.5
                output_extension:
                  type: string
                  enum:
                    - mp3
                    - wav
                    - flac
                    - ogg
                    - aac
                    - webm
                  description: Desired output format.
                  example: mp3
                webhook_url:
                  type: string
                  description: Callback URL for async processing results.
                  example: http://your-webhook-url.com/callback
              required:
                - speed_change_factor
              anyOf:
                - required:
                    - audio_url
                - required:
                    - audio_file
      responses:
        '200':
          description: Successfully initiated audio speed change
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                  conversion_id:
                    type: string
                  credit_estimate:
                    type: number
                    format: float
                  conversion_path:
                    type: string
                  message:
                    type: string
                example:
                  success: true
                  conversion_id: conv999
                  credit_estimate: 45
                  conversion_path: https://example.com/output/converted_audio.mp3
                  message: Speed change task queued successfully
        '400':
          description: Invalid parameters
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                    example: false
                  error:
                    type: string
                    example: Invalid speed_change_factor
        '401':
          description: Invalid authentication
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                    example: false
                  error:
                    type: string
                    example: Authentication failed
        '402':
          description: Insufficient credits
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                    example: false
                  error:
                    type: string
                    example: Insufficient credits for this operation
                  required_credits:
                    type: number
                    example: 45
                  available_credits:
                    type: number
                    example: 30
        '404':
          description: User or plan not found
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                    example: false
                  error:
                    type: string
                    example: User subscription plan not found
        '500':
          description: Internal server error
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                    example: false
                  error:
                    type: string
                    example: Internal server error during processing
      security:
        - ApiKeyAuth: []
      x-codeSamples:
        - lang: Python
          source: |-
            import requests

            url = "https://api.musicgpt.com/api/public/v1/audio_speed_changer"
            headers = {"Authorization": "<API_KEY>"}

            # Option 1: Use audio URL
            payload = {
                "audio_url": "https://example.com/input_audio.mp3",
                "speed_change_factor": 1.5,
                "output_extension": "mp3"
            }
            response = requests.post(url, headers=headers, data=payload)
            print(response.json())

            # Option 2: Upload local audio file
            payload = {
                "speed_change_factor": 1.25,
                "output_extension": "wav"
            }
            with open("input_audio.mp3", "rb") as f:
                files = {"audio_file": f}
                response = requests.post(url, headers=headers, data=payload, files=files)
            print(response.json())
        - lang: PHP
          source: |-
            <?php
            $url = 'https://api.musicgpt.com/api/public/v1/audio_speed_changer';
            $headers = ['Authorization: <API_KEY>'];

            $data = [
                'audio_url' => 'https://example.com/input_audio.mp3',
                'speed_change_factor' => 1.5,
                'output_extension' => 'mp3'
            ];

            $ch = curl_init($url);
            curl_setopt($ch, CURLOPT_POST, true);
            curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
            curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
            curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
            $response = curl_exec($ch);
            curl_close($ch);
            echo $response;
        - lang: Go
          source: "package main\n\nimport (\n\t\"fmt\"\n\t\"io\"\n\t\"net/http\"\n\t\"strings\"\n)\n\nfunc main() {\n\turl := \"https://api.musicgpt.com/api/public/v1/audio_speed_changer\"\n\ttoken := \"<API_KEY>\"\n\tdata := \"audio_url=https://example.com/input_audio.mp3&speed_change_factor=1.5&output_extension=mp3\"\n\n\treq, _ := http.NewRequest(\"POST\", url, strings.NewReader(data))\n\treq.Header.Add(\"Authorization\", token)\n\tres, _ := http.DefaultClient.Do(req)\n\tdefer res.Body.Close()\n\tbody, _ := io.ReadAll(res.Body)\n\tfmt.Println(string(body))\n}"
        - lang: Java
          source: // Java version omitted for brevity; request if needed.
components:
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: header
      name: Authorization

````