# Encode a fade effect between concatenated video files.

[🤖/video/concat](/docs/robots/video-concat.md) enables you to concatenate together all your video files quickly and easily whilst encoding a fade effect between each clip.

If you were looking for a way to add some extra flair to your concatenated videos you are in luck. With this demo, we are going to show how adding both the `video_fade_seconds` and`audio_fade_seconds` parameters can make all the difference. As well, we are going to look into how we can overcome the parameters shortcoming of not adding a fade effect at the beginning of your videos using the `ffmpeg` parameter.

To make sure we have everything all set up as needed for our concatenation to take place, we first need to resize both of our video clips. We do this by passing both our imported videos to[🤖/video/encode](/docs/robots/video-encode.md) making sure we set the same dimensions and `preset`value.

Now we have both our files prepared we can pass them to[🤖/video/concat](/docs/robots/video-concat.md). Within our `use` parameter we set up both the `name`value of our previously resized step, along with an `as` value. When concatenating videos the order they are set in is specified by how we set up by our `as` value, so for example`as: "video_1"` would come before `as: "video_2"`.

To add our fancy fade effect we set up both the `video_fade_seconds` and `audio_fade_seconds`parameters with values to specify how long we want these transitions to last between each video file. These parameters allow you to seamlessly create both an audio and video fade effect between your video files. This even allows for millisecond values to be represented by using decimal values. So if you wanted the fade effect to last 750 milliseconds, you would select 0.75.

With our fade effects in place, why don't we add a video fade at the beginning of our video? Because[🤖/video/concat](/docs/robots/video-concat.md) works by using[FFMpeg⁠](https://ffmpeg.org/ffmpeg-filters.html), if we try add any additional `vf` parameter values, this will result in a error. So to bypass this, we need to pass our concatenate step to[🤖/video/encode](/docs/robots/video-encode.md). We have already encoded our videos `preset` value in our previous step, so no need to do that again. Simply add a `preset` parameter, and set its value to `empty` so the Robot can run as intended.

Using our `ffmpeg` parameter, we set up a `vf` parameter and set its value to`fade=type=in:duration=1`. This creates a video fade-in effect at the start of our final file.

Now with everything set up, we are good to run and see the final result. Happy Encoding!

Step 1

### Handle uploads

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

[kite10.mp4](https://demos.transloadit.com/6a/2169a9483f46d9a6e7aee457c1c1ae/kite10.mp4)

Video · 2.0 MB · 13s · 1024 × 768

```
":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

### Import files from web servers

We are happy to import from whatever storage solution suits you best. [Learn more ›](/services/file-importing.md)

[waves10.mp4](https://demos.transloadit.com/23/3bc376c80545fcbcc12c327423ad9d/waves10.mp4)

Video · 1.9 MB · 13s · 1024 × 768

```
"preroll_imported": {
  "robot": "/http/import",
  "result": true,
  "url": "https://demos.transloadit.com/inputs/waves10.mp4"
}
```

🤖 [/http/import](/docs/robots/http-import.md)

This bot imports any file that is publicly available via a web URL into Transloadit

Step 3

### Transcode, resize, or watermark videos

We offer a variety of video encoding features like optimizing for different devices, merging, injecting ads, changing audio tracks, or adding company logos. [Learn more ›](/services/video-encoding.md)

[waves10.mp4](https://demos.transloadit.com/c4/ad28f2653b45659a734ab86b7e866f/waves10.mp4)

Video · 2.0 MB · 13s · 480 × 270

```
"preroll_resized": {
  "use": "preroll_imported",
  "robot": "/video/encode",
  "result": true,
  "background": "#00000000",
  "ffmpeg_stack": "v7",
  "height": 270,
  "preset": "ipad-high",
  "resize_strategy": "pad",
  "turbo": false,
  "width": 480
}
```

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

This bot encodes, resizes, applies watermarks to videos and animated GIFs

Step 4

### Transcode, resize, or watermark videos

We offer a variety of video encoding features like optimizing for different devices, merging, injecting ads, changing audio tracks, or adding company logos. [Learn more ›](/services/video-encoding.md)

[kite10.mp4](https://demos.transloadit.com/8a/9aaf5b88bb44b1a47a64103b1c9dfa/kite10.mp4)

Video · 2.1 MB · 13s · 480 × 270

```
"original_resized": {
  "use": ":original",
  "robot": "/video/encode",
  "result": true,
  "background": "#00000000",
  "ffmpeg_stack": "v7",
  "height": 270,
  "preset": "ipad-high",
  "resize_strategy": "pad",
  "turbo": false,
  "width": 480
}
```

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

This bot encodes, resizes, applies watermarks to videos and animated GIFs

Step 5

### Concatenate videos

We offer a variety of video encoding features like optimizing for different devices, merging, injecting ads, changing audio tracks, or adding company logos. [Learn more ›](/services/video-encoding.md)

[kite10\_waves10.mp4](https://demos.transloadit.com/99/49608f15a54334a5699c6df8f16a9d/kite10%5Fwaves10.mp4)

Video · 4.0 MB · 26s · 1024 × 768

```
"concatenated": {
  "use": {
    "steps": [
      {
        "name": "original_resized",
        "as": "video_1"
      },
      {
        "name": "preroll_resized",
        "as": "video_2"
      }
    ]
  },
  "robot": "/video/concat",
  "result": true,
  "audio_fade_seconds": 1,
  "ffmpeg_stack": "v7",
  "preset": "ipad-high",
  "video_fade_seconds": 1
}
```

🤖 [/video/concat](/docs/robots/video-concat.md)

This bot concatenates several videos together

Step 6

### Transcode, resize, or watermark videos

We offer a variety of video encoding features like optimizing for different devices, merging, injecting ads, changing audio tracks, or adding company logos. [Learn more ›](/services/video-encoding.md)

[kite10\_waves10.mp4](https://demos.transloadit.com/00/5f59baccf64973818fc2d0ceb1c8c4/kite10%5Fwaves10.mp4)

Video · 2.5 MB · 26s · 1024 × 768

```
"encode": {
  "use": "concatenated",
  "robot": "/video/encode",
  "ffmpeg": {
    "vf": "fade=type=in:duration=1"
  },
  "ffmpeg_stack": "v7",
  "preset": "empty",
  "turbo": false
}
```

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

This bot encodes, resizes, applies watermarks to videos and animated GIFs

Step 7

### 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/6a/2169a9483f46d9a6e7aee457c1c1ae/kite10.mp4⁠](https://demos.transloadit.com/6a/2169a9483f46d9a6e7aee457c1c1ae/kite10.mp4)

`preroll_imported`

* [https://demos.transloadit.com/23/3bc376c80545fcbcc12c327423ad9d/waves10.mp4⁠](https://demos.transloadit.com/23/3bc376c80545fcbcc12c327423ad9d/waves10.mp4)

`preroll_resized`

* [https://demos.transloadit.com/c4/ad28f2653b45659a734ab86b7e866f/waves10.mp4⁠](https://demos.transloadit.com/c4/ad28f2653b45659a734ab86b7e866f/waves10.mp4)

`original_resized`

* [https://demos.transloadit.com/8a/9aaf5b88bb44b1a47a64103b1c9dfa/kite10.mp4⁠](https://demos.transloadit.com/8a/9aaf5b88bb44b1a47a64103b1c9dfa/kite10.mp4)

`concatenated`

* [https://demos.transloadit.com/99/49608f15a54334a5699c6df8f16a9d/kite10\_waves10.mp4⁠](https://demos.transloadit.com/99/49608f15a54334a5699c6df8f16a9d/kite10%5Fwaves10.mp4)

`encode`

* [https://demos.transloadit.com/00/5f59baccf64973818fc2d0ceb1c8c4/kite10\_waves10.mp4⁠](https://demos.transloadit.com/00/5f59baccf64973818fc2d0ceb1c8c4/kite10%5Fwaves10.mp4)

```
"exported": {
  "use": [
    "preroll_imported",
    "preroll_resized",
    "original_resized",
    "concatenated",
    "encode",
    ":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',
            },
            preroll_imported: {
              robot: '/http/import',
              result: true,
              url: 'https://demos.transloadit.com/inputs/waves10.mp4',
            },
            preroll_resized: {
              use: 'preroll_imported',
              robot: '/video/encode',
              result: true,
              background: '#00000000',
              ffmpeg_stack: 'v7',
              height: 270,
              preset: 'ipad-high',
              resize_strategy: 'pad',
              turbo: false,
              width: 480,
            },
            original_resized: {
              use: ':original',
              robot: '/video/encode',
              result: true,
              background: '#00000000',
              ffmpeg_stack: 'v7',
              height: 270,
              preset: 'ipad-high',
              resize_strategy: 'pad',
              turbo: false,
              width: 480,
            },
            concatenated: {
              use: {
                steps: [
                  {
                    name: 'original_resized',
                    as: 'video_1',
                  },
                  {
                    name: 'preroll_resized',
                    as: 'video_2',
                  },
                ],
              },
              robot: '/video/concat',
              result: true,
              audio_fade_seconds: 1,
              ffmpeg_stack: 'v7',
              preset: 'ipad-high',
              video_fade_seconds: 1,
            },
            encode: {
              use: 'concatenated',
              robot: '/video/encode',
              ffmpeg: {
                vf: 'fade=type=in:duration=1',
              },
              ffmpeg_stack: 'v7',
              preset: 'empty',
              turbo: false,
            },
            exported: {
              use: ['preroll_imported', 'preroll_resized', 'original_resized', 'concatenated', 'encode', ':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→Video EncodingAdd an audio track to video footage](/demos/video-encoding/add-audio-track-to-video-footage.md)
* [View demo→Video EncodingAdd an empty audio track to still video](/demos/video-encoding/add-empty-audio-track-to-still-video.md)
* [View demo→Document ProcessingAdd a header or footer to a PDF](/demos/document-processing/add-header-or-footer-to-pdf.md)

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