# Fade in and out audio file

Using [custom FFmpeg parameters](/docs/robots/video-encode.md#ffmpeg-parameters-video-encode)Transloadit can encode your media files in a variety of ways. In this demo, we are going to show how using our API you can trim an audio file, have it fade-in at the beginning, and fade-out at the end.

When encoding media files of any kind, it is always important to have full control of your operation so that you can get exactly what you are looking for. Luckily, we have just the tool we need to encode our audio files to perfection. Using our `ffmpeg` parameter we have numerous encoding options to our disposal. Let's break down what each `ffmpeg` parameter is doing.

Using FFMpeg's `af` parameter, we can do some pretty neat things when encoding audio files. When we combine it with the `afade` parameter we can set fade-in and fade-out options. We use its embedded`st` parameter to select where the fade effect starts, and to determine how long the fade effect lasts till volume is back to normal we use the `d` parameter.

The second FFMpeg parameter we use is the `to` parameter. This allows us to trim our file to the length we want by setting the duration of our file.

:bulb: combining the `ss` parameter with the `to` parameter, allows you to specify a clip from an audio file to be extracted, as shown in this[demo](/demos/audio-encoding/take-a-10-seconds-clip-of-an-audio-file.md). However, we will not be needing that today as we want our fade-in effect to start right at the beginning of our file.

Along with these parameters we also use our `mp3` [preset](/docs/presets/audio.md).

Step 1

### Handle uploads

We can handle uploads of your users directly. [Learn more ›](/services/handling-uploads.md)

[joakim\_karud-rock\_angel.mp3](https://demos.transloadit.com/15/1307a76c5c41ee8fc8208ae310f955/joakim%5Fkarud-rock%5Fangel.mp3)

Audio · 8.9 MB · 233s

```
":original": {
  "robot": "/upload/handle"
}
```

🤖 [/upload/handle](/docs/robots/upload-handle.md)

This bot receives uploads that your users throw at you from browser or apps, or that you throw at us programmatically

Step 2

### Encode audio

We offer a variety of features to reduce audio size while maintaining quality, as well as add effects like loops or watermarks. [Learn more ›](/services/audio-encoding.md)

[joakim\_karud-rock\_angel.mp3](https://demos.transloadit.com/e3/0ecdc0e6274b9f8b2f768b2e928596/joakim%5Fkarud-rock%5Fangel.mp3)

Audio · 251 KB · 16s

```
"encode_audio": {
  "use": ":original",
  "robot": "/audio/encode",
  "result": true,
  "ffmpeg": {
    "af": "afade=t=in:st=0:d=4, afade=t=out:st=13:d=3",
    "to": "16"
  },
  "ffmpeg_stack": "v7",
  "preset": "mp3"
}
```

🤖 [/audio/encode](/docs/robots/audio-encode.md)

This bot converts audio files into all kinds of formats for you. We provide encoding presets for the most common formats

Step 3

### Export files to Amazon S3

We export to the storage platform of your choice. [Learn more ›](/services/file-exporting.md)

`:original`

* [https://demos.transloadit.com/15/1307a76c5c41ee8fc8208ae310f955/joakim\_karud-rock\_angel.mp3⁠](https://demos.transloadit.com/15/1307a76c5c41ee8fc8208ae310f955/joakim%5Fkarud-rock%5Fangel.mp3)

`encode_audio`

* [https://demos.transloadit.com/e3/0ecdc0e6274b9f8b2f768b2e928596/joakim\_karud-rock\_angel.mp3⁠](https://demos.transloadit.com/e3/0ecdc0e6274b9f8b2f768b2e928596/joakim%5Fkarud-rock%5Fangel.mp3)

```
"exported": {
  "use": [
    "encode_audio",
    ":original"
  ],
  "robot": "/s3/store",
  "credentials": "demo_s3_credentials",
  "url_prefix": "https://demos.transloadit.com/"
}
```

🤖 [/s3/store](/docs/robots/s3-store.md)

This bot exports encoding results to Amazon S3

## Live Demo. See for yourself

Loading Uppy demo…

This live demo is powered by [Uppy⁠](https://uppy.io/docs/guides/uppy-transloadit/), our open source file uploader that you can also use without Transloadit, and [tus⁠](https://tus.io), our open protocol for resumable file uploads that is making uploading more reliable across the world.

## Build this in your own language

```
<!-- This pulls Uppy from our CDN -->
<!-- For smaller self-hosted bundles, install Uppy and plugins manually: -->
<!-- npm i --save @uppy/core @uppy/dashboard @uppy/remote-sources @uppy/transloadit ... -->
<link
  href="https://releases.transloadit.com/uppy/v3.10.0/uppy.min.css"
  rel="stylesheet"
/>
<button id="browse">Select Files</button>
<script type="module">
  import {
    Uppy,
    Dashboard,
    ImageEditor,
    RemoteSources,
    Transloadit,
  } from 'https://releases.transloadit.com/uppy/v3.10.0/uppy.min.mjs'
  const uppy = new Uppy()
    .use(Transloadit, {
      waitForEncoding: true,
      alwaysRunAssembly: true,
      assemblyOptions: {
        params: {
          // It's often better store encoding instructions in your account
          // and use a `template_id` instead of adding these steps inline
          steps: {
            ':original': {
              robot: '/upload/handle',
            },
            encode_audio: {
              use: ':original',
              robot: '/audio/encode',
              result: true,
              ffmpeg: {
                af: 'afade=t=in:st=0:d=4, afade=t=out:st=13:d=3',
                to: '16',
              },
              ffmpeg_stack: 'v7',
              preset: 'mp3',
            },
            exported: {
              use: ['encode_audio', ':original'],
              robot: '/s3/store',
              credentials: 'demo_s3_credentials',
              url_prefix: 'https://demos.transloadit.com/',
            },
          },
        },
      },
    })
    .use(Dashboard, { trigger: '#browse' })
    .use(ImageEditor, { target: Dashboard })
    .use(RemoteSources, {
      companionUrl: 'https://api2.transloadit.com/companion',
    })
    .on('complete', ({ transloadit }) => {
      // Due to `waitForEncoding:true` this is fired after encoding is done.
      // Alternatively, set `waitForEncoding` to `false` and provide a `notify_url`
      console.log(transloadit) // Array of Assembly Statuses
      for (const assembly of transloadit) {
        console.log(assembly.results) // Array of all encoding results
      }
    })
    .on('error', (error) => {
      console.error(error)
    })
</script>

```

[Read docs: Browsers](/docs/sdks/uppy.md)

## So many ways to integrate

Transloadit is a service for companies with developers. And there are many ways developers can put Transloadit to good use inside your company to automate media processing.

#### Bulk imports

Add one of our [import Robots](/services/file-importing.md) to acquire and transcode massive media libraries.

#### Handling uploads

We are *the* experts at reliably [handling uploads](/services/handling-uploads.md). We wrote the [protocol⁠](https://tus.io/) for it.

#### Front-end integration

We integrate with web browsers via our next-gen file uploader [Uppy⁠](https://uppy.io/docs/guides/uppy-transloadit/) and SDKs for Android and iOS.

#### Back-end integration

Send us batch jobs in any server language using one of our [SDKs](/docs/sdks.md) or directly interfacing with our [REST API](/docs/api.md).

#### Pingbacks

Configure a [notify\_url](/services/content-delivery.md) to let your server receive transcoding results JSON in the `transloadit` POST field.

#### On-demand

Use our [Smart CDN](/services/file-importing.md) to adapt files on-demand and stream them directly to your users.

[Browsers](/docs/sdks/uppy.md)[TransloaditKit](/docs/sdks/transloaditkit.md)[Ruby SDK](/docs/sdks/ruby-sdk.md)[HTTP REST API](/docs/api.md)[Python SDK](/docs/sdks/python-sdk.md)[PHP SDK](/docs/sdks/php-sdk.md)[Node.js SDK](/docs/sdks/node-sdk.md)[Java SDK](/docs/sdks/java-sdk.md)[Go SDK](/docs/sdks/go-sdk.md)[cURL](/docs/sdks/curl.md)[Convex](/docs/sdks/convex.md)

[Browsers](/docs/sdks/uppy.md)[TransloaditKit](/docs/sdks/transloaditkit.md)[Ruby SDK](/docs/sdks/ruby-sdk.md)[HTTP REST API](/docs/api.md)[Python SDK](/docs/sdks/python-sdk.md)[PHP SDK](/docs/sdks/php-sdk.md)[Node.js SDK](/docs/sdks/node-sdk.md)[Java SDK](/docs/sdks/java-sdk.md)[Go SDK](/docs/sdks/go-sdk.md)[cURL](/docs/sdks/curl.md)[Convex](/docs/sdks/convex.md)

[Browsers](/docs/sdks/uppy.md)[TransloaditKit](/docs/sdks/transloaditkit.md)[Ruby SDK](/docs/sdks/ruby-sdk.md)[HTTP REST API](/docs/api.md)[Python SDK](/docs/sdks/python-sdk.md)[PHP SDK](/docs/sdks/php-sdk.md)[Node.js SDK](/docs/sdks/node-sdk.md)[Java SDK](/docs/sdks/java-sdk.md)[Go SDK](/docs/sdks/go-sdk.md)[cURL](/docs/sdks/curl.md)[Convex](/docs/sdks/convex.md)

## Other cool demos

* [View demo→Audio EncodingAdd echo to an audio file](/demos/audio-encoding/ffmpeg-add-echo.md)
* [View demo→Audio EncodingAdd watermark to a song](/demos/audio-encoding/implement-audio-watermarking.md)
* [View demo→Document ProcessingAdd a header or footer to a PDF](/demos/document-processing/add-header-or-footer-to-pdf.md)

Try Transloadit

## Ready to get started?

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