Convert videos to HLS and MPEG-Dash

🤖/video/adaptive encodes videos into HTTP Live Streaming (HLS) and MPEG-Dash supported formats and generates the necessary manifest and playlist files.

This Robot accepts all types of video files and audio files. Do not forget to use Step bundling in your use parameter to make the Robot work on several input files at once.

This Robot is normally used in combination with 🤖/video/encode. We have implemented video and audio encoding presets specifically for MPEG-Dash and HTTP Live Streaming support. These presets are prefixed with "dash/" and "hls/". View a HTTP Live Streaming demo here.

Required CORS settings for MPEG-Dash and HTTP Live Streaming

Playing back MPEG-Dash Manifest or HLS playlist files requires a proper CORS setup on the server-side. The file-serving server should be configured to add the following header fields to responses:

Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET
Access-Control-Allow-Headers: *

If the files are stored in an Amazon S3 Bucket, you can use the following CORS definition to ensure the CORS header fields are set correctly:

[
  {
    "AllowedHeaders": ["*"],
    "AllowedMethods": ["GET"],
    "AllowedOrigins": ["*"],
    "ExposeHeaders": []
  }
]

To set up CORS for your S3 bucket:

Visit https://s3.console.aws.amazon.com/s3/buckets/
Click on your bucket
Click "Permissions"
Edit "Cross-origin resource sharing (CORS)"

Storing Segments and Playlist files

The Robot gives its result files (segments, initialization segments, MPD manifest files and M3U8 playlist files) the right metadata property relative_path, so that you can store them easily using one of our storage Robots.

In the path parameter of the storage Robot of your choice, use the Assembly Variable ${file.meta.relative_path} to store files in the proper paths to make the playlist files work.

Usage example

Implementing HTTP Live Streaming: encode the uploaded video into three versions, then cut them into several segments and generate playlist files containing all the segments:

{
  "steps": {
    ":original": {
      "robot": "/upload/handle"
    },
    "encoded_480p": {
      "robot": "/video/encode",
      "use": ":original",
      "preset": "hls/480p",
      "ffmpeg_stack": "v6"
    },
    "encoded_720p": {
      "robot": "/video/encode",
      "use": ":original",
      "preset": "hls/720p",
      "ffmpeg_stack": "v6"
    },
    "encoded_1080p": {
      "robot": "/video/encode",
      "use": ":original",
      "preset": "hls/1080p",
      "ffmpeg_stack": "v6"
    },
    "hls_bundled": {
      "robot": "/video/adaptive",
      "use": {
        "steps": [
          "encoded_480p",
          "encoded_720p",
          "encoded_1080p"
        ],
        "bundle_steps": true
      },
      "technique": "hls",
      "playlist_name": "my_playlist.m3u8"
    }
  }
}

Parameters

interpolate
boolean | Record<string, boolean>
Controls whether Assembly Variables are interpolated for individual instruction fields.

By default, most Robot instruction fields interpolate Assembly Variables. Set this to false to treat every instruction field as literal text, or set an individual field path to false to treat only that field as literal text. For Robot-specific fields that are literal by default, set this to true or set that field path to true to opt back into interpolation.

Use field names such as path, or dotted paths such as ffmpeg.vf for nested objects.
output_meta
Record<string, boolean> | boolean | Array<string>
Allows you to specify a set of metadata that is more expensive on CPU power to calculate, and thus is disabled by default to keep your Assemblies processing fast.

For images, you can add "has_transparency": true in this object to extract if the image contains transparent parts and "dominant_colors": true to extract an array of hexadecimal color codes from the image.

For images, you can also add "blurhash": true to extract a BlurHash string — a compact representation of a placeholder for the image, useful for showing a blurred preview while the full image loads.

For videos, you can add the "colorspace: true" parameter to extract the colorspace of the output video.

For videos, you can also add "interlaced": true to detect whether the video is interlaced. This combines the cheap ffprobe field_order flag with a bounded idet sampling pass over the first frames of the source, exposing interlaced, field_order, and a diagnostic interlace_detection object under file.meta. This is computationally expensive and billed accordingly.

For audio, you can add "mean_volume": true to get a single value representing the mean average volume of the audio file.

You can also set this to false to skip metadata extraction and speed up transcoding.
result
boolean (default: false)
Whether the results of this Step should be present in the Assembly Status JSON
queue
batch
Setting the queue to 'batch', manually downgrades the priority of jobs for this step to avoid consuming Priority job slots for jobs that don't need zero queue waiting times
force_accept
boolean (default: false)
Force a Robot to accept a file type it would have ignored.

By default, Robots ignore files they are not familiar with. 🤖/video/encode, for example, will happily ignore input images.

With the force_accept parameter set to true, you can force Robots to accept all files thrown at them. This will typically lead to errors and should only be used for debugging or combatting edge cases.
ignore_errors
boolean | Array<meta | execute> (default: [])
Ignore errors during specific phases of processing.

Setting this to ["meta"] will cause the Robot to ignore errors during metadata extraction.

Setting this to ["execute"] will cause the Robot to ignore errors during the main execution phase.

Setting this to true is equivalent to ["meta", "execute"] and will ignore errors in both phases.
use
string | Array<string> | Array<object> | object
Specifies which Step(s) to use as input.
- You can pick any names for Steps except ":original" (reserved for user uploads handled by Transloadit)
- You can provide several Steps as input with arrays:
```
{
  "use": [
    ":original",
    "encoded",
    "resized"
  ]
}
```
- You can also tag an input Step with as to pass semantic intent to robots:
- You can also tag input Steps with as to pass semantic intent to robots:
```
{
  "use": [
    {
      "name": ":original",
      "as": "image"
    },
    {
      "name": ":original",
      "as": "mask"
    }
  ]
}
```
Tip

That's likely all you need to know about use, but you can view Advanced use cases.
ffmpeg
object
A parameter object to be passed to FFmpeg. If a preset is used, the options specified are merged on top of the ones from the preset. For available options, see the FFmpeg documentation. Options specified here take precedence over the preset options.
ffmpeg_stack
v6 | v7 | v8 | string (default: "v6.0.0")
Selects the FFmpeg stack version to use for encoding. These versions reflect real FFmpeg versions. We currently recommend to use "v6.0.0". Deprecated "v5.x" values are accepted for backward compatibility.
width
string | number | null
Width of the new video, in pixels.

If the value is not specified and the preset parameter is available, the preset's supplied width will be implemented.
height
string | number | null
Height of the new video, in pixels.

If the value is not specified and the preset parameter is available, the preset's supplied height will be implemented.
preset
android | android-high | android-low | android_high | android_low | dash-1080p-video | dash-1080p_video |
Converts a video according to pre-configured settings.

If you specify your own FFmpeg parameters using the Robot's and/or do not not want Transloadit to set any encoding setting, starting ffmpeg_stack: "v6", you can use the value 'empty' here.
technique
dash | hls | cmaf (default: "dash")
Determines which streaming technique should be used. Supports "dash" for MPEG-Dash, "hls" for HTTP Live Streaming and "cmaf" for FFmpeg-based CMAF output with both MPEG-Dash and HLS manifests that reference the same fMP4 segments.
playlist_name
string
The filename for the generated manifest/playlist file. The default is "playlist.mpd" if your technique is "dash", and "playlist.m3u8" if your technique is "hls". For "cmaf", this value names the MPEG-Dash manifest and defaults to "playlist.mpd".
hls_playlist_name
string
Only used when technique is "cmaf". Defines the filename for the generated HLS master playlist. The default is "playlist.m3u8".
segment_duration
string | number (default: 10)
The duration for each segment in seconds.
closed_captions
boolean (default: true)
Determines whether you want closed caption support when using the "hls" technique.
audio_group
boolean (default: false)
When set to true and using the "hls" technique, audio-only input files are treated as alternate audio renditions instead of standalone stream variants. This enables players to offer audio track selection (e.g. for multiple languages). Audio-only files are listed as #EXT-X-MEDIA:TYPE=AUDIO entries in the multivariant playlist, and video variants reference them via the AUDIO attribute.

When enabled, video inputs only include their video stream in the output segments (any muxed audio is excluded). Provide audio separately as audio-only input files.

This option is only supported for the "hls" technique and has no effect when using "dash".

Demos

Introducing MPEG-DASH support for adaptive streaming October 11, 2016
New pricing model for future Transloadit customers February 7, 2018
Guide to encoding videos for streaming with Transloadit April 28, 2020
What is HLS? January 23, 2024
Save costs with on-demand video encoding May 5, 2025

Usage example

Implementing HTTP Live Streaming: encode the uploaded video into three versions, then cut them into several segments and generate playlist files containing all the segments:

{
  "steps": {
    ":original": {
      "robot": "/upload/handle"
    },
    "encoded_480p": {
      "robot": "/video/encode",
      "use": ":original",
      "preset": "hls/480p",
      "ffmpeg_stack": "v6"
    },
    "encoded_720p": {
      "robot": "/video/encode",
      "use": ":original",
      "preset": "hls/720p",
      "ffmpeg_stack": "v6"
    },
    "encoded_1080p": {
      "robot": "/video/encode",
      "use": ":original",
      "preset": "hls/1080p",
      "ffmpeg_stack": "v6"
    },
    "hls_bundled": {
      "robot": "/video/adaptive",
      "use": {
        "steps": [
          "encoded_480p",
          "encoded_720p",
          "encoded_1080p"
        ],
        "bundle_steps": true
      },
      "technique": "hls",
      "playlist_name": "my_playlist.m3u8"
    }
  }
}

Parameters

`interpolate`

boolean | Record<string, boolean>

Controls whether Assembly Variables are interpolated for individual instruction fields.

By default, most Robot instruction fields interpolate Assembly Variables. Set this to false to treat every instruction field as literal text, or set an individual field path to false to treat only that field as literal text. For Robot-specific fields that are literal by default, set this to true or set that field path to true to opt back into interpolation.

Use field names such as path, or dotted paths such as ffmpeg.vf for nested objects.

`output_meta`

Record<string, boolean> | boolean | Array<string>

Allows you to specify a set of metadata that is more expensive on CPU power to calculate, and thus is disabled by default to keep your Assemblies processing fast.

For images, you can add "has_transparency": true in this object to extract if the image contains transparent parts and "dominant_colors": true to extract an array of hexadecimal color codes from the image.

For images, you can also add "blurhash": true to extract a BlurHash string — a compact representation of a placeholder for the image, useful for showing a blurred preview while the full image loads.

For videos, you can add the "colorspace: true" parameter to extract the colorspace of the output video.

For videos, you can also add "interlaced": true to detect whether the video is interlaced. This combines the cheap ffprobe field_order flag with a bounded idet sampling pass over the first frames of the source, exposing interlaced, field_order, and a diagnostic interlace_detection object under file.meta. This is computationally expensive and billed accordingly.

For audio, you can add "mean_volume": true to get a single value representing the mean average volume of the audio file.

You can also set this to false to skip metadata extraction and speed up transcoding.

`result`

boolean (default: false)

Whether the results of this Step should be present in the Assembly Status JSON

`queue`

batch

Setting the queue to 'batch', manually downgrades the priority of jobs for this step to avoid consuming Priority job slots for jobs that don't need zero queue waiting times

`force_accept`

boolean (default: false)

Force a Robot to accept a file type it would have ignored.

By default, Robots ignore files they are not familiar with. 🤖/video/encode, for example, will happily ignore input images.

With the force_accept parameter set to true, you can force Robots to accept all files thrown at them. This will typically lead to errors and should only be used for debugging or combatting edge cases.

`ignore_errors`

boolean | Array<meta | execute> (default: [])

Ignore errors during specific phases of processing.

Setting this to ["meta"] will cause the Robot to ignore errors during metadata extraction.

Setting this to ["execute"] will cause the Robot to ignore errors during the main execution phase.

Setting this to true is equivalent to ["meta", "execute"] and will ignore errors in both phases.

`use`

string | Array<string> | Array<object> | object

Specifies which Step(s) to use as input.

You can pick any names for Steps except ":original" (reserved for user uploads handled by Transloadit)

You can provide several Steps as input with arrays:

{
  "use": [
    ":original",
    "encoded",
    "resized"
  ]
}

You can also tag an input Step with as to pass semantic intent to robots:

You can also tag input Steps with as to pass semantic intent to robots:

{
  "use": [
    {
      "name": ":original",
      "as": "image"
    },
    {
      "name": ":original",
      "as": "mask"
    }
  ]
}

Tip

That's likely all you need to know about use, but you can view Advanced use cases.

`ffmpeg`

object

A parameter object to be passed to FFmpeg. If a preset is used, the options specified are merged on top of the ones from the preset. For available options, see the FFmpeg documentation. Options specified here take precedence over the preset options.

`ffmpeg_stack`

v6 | v7 | v8 | string (default: "v6.0.0")

Selects the FFmpeg stack version to use for encoding. These versions reflect real FFmpeg versions. We currently recommend to use "v6.0.0". Deprecated "v5.x" values are accepted for backward compatibility.

`width`

string | number | null

Width of the new video, in pixels.

If the value is not specified and the preset parameter is available, the preset's supplied width will be implemented.

`height`

string | number | null

Height of the new video, in pixels.

If the value is not specified and the preset parameter is available, the preset's supplied height will be implemented.

`preset`

Converts a video according to pre-configured settings.

If you specify your own FFmpeg parameters using the Robot's and/or do not not want Transloadit to set any encoding setting, starting ffmpeg_stack: "v6", you can use the value 'empty' here.

`technique`

dash | hls | cmaf (default: "dash")

Determines which streaming technique should be used. Supports "dash" for MPEG-Dash, "hls" for HTTP Live Streaming and "cmaf" for FFmpeg-based CMAF output with both MPEG-Dash and HLS manifests that reference the same fMP4 segments.

`playlist_name`

string

The filename for the generated manifest/playlist file. The default is "playlist.mpd" if your technique is "dash", and "playlist.m3u8" if your technique is "hls". For "cmaf", this value names the MPEG-Dash manifest and defaults to "playlist.mpd".

`hls_playlist_name`

string

Only used when technique is "cmaf". Defines the filename for the generated HLS master playlist. The default is "playlist.m3u8".

`segment_duration`

string | number (default: 10)

The duration for each segment in seconds.

`closed_captions`

boolean (default: true)

Determines whether you want closed caption support when using the "hls" technique.

`audio_group`

boolean (default: false)

When set to true and using the "hls" technique, audio-only input files are treated as alternate audio renditions instead of standalone stream variants. This enables players to offer audio track selection (e.g. for multiple languages). Audio-only files are listed as #EXT-X-MEDIA:TYPE=AUDIO entries in the multivariant playlist, and video variants reference them via the AUDIO attribute.

When enabled, video inputs only include their video stream in the output segments (any muxed audio is excluded). Provide audio separately as audio-only input files.

This option is only supported for the "hls" technique and has no effect when using "dash".

Convert videos to HLS and MPEG-Dash

Required CORS settings for MPEG-Dash and HTTP Live Streaming

Storing Segments and Playlist files

Usage example

Parameters

interpolate

output_meta

result

queue

force_accept

ignore_errors

use

Tip

ffmpeg

ffmpeg_stack

width

height

preset

technique

playlist_name

hls_playlist_name

segment_duration

closed_captions

audio_group

Demos

Related blog posts

Required CORS settings for MPEG-Dash and HTTP Live Streaming

Storing Segments and Playlist files

Usage example

Parameters

interpolate

output_meta

result

queue

force_accept

ignore_errors

use

Tip

ffmpeg

ffmpeg_stack

width

height

preset

technique

playlist_name

hls_playlist_name

segment_duration

closed_captions

audio_group

Demos

Related blog posts

`interpolate`

`output_meta`

`result`

`queue`

`force_accept`

`ignore_errors`

`use`

`ffmpeg`

`ffmpeg_stack`

`width`

`height`

`preset`

`technique`

`playlist_name`

`hls_playlist_name`

`segment_duration`

`closed_captions`

`audio_group`

`interpolate`

`output_meta`

`result`

`queue`

`force_accept`

`ignore_errors`

`use`

`ffmpeg`

`ffmpeg_stack`

`width`

`height`

`preset`

`technique`

`playlist_name`

`hls_playlist_name`

`segment_duration`

`closed_captions`

`audio_group`