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Convert videos to HLS and MPEG-Dash

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

The /video/adaptive Robot generates the necessary manifest and playlist files based on a set of used video and audio files to make implementing HTTP Live Streaming (HLS) and MPEG-Dash streaming easy.

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.

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".

We deem this Robot ready for production, but since it hasn't seen a lot of such traffic yet, it's still labeled as beta.

Required CORS settings for MPEG-Dash

Playing back MPEG-Dash Manifest files requires CORS definitions on your Amazon S3 Bucket or other storage location. For convenience here you can find a working CORS definition:

<CORSConfiguration>
  <CORSRule>
    <AllowedOrigin>*</AllowedOrigin>
    <AllowedMethod>GET</AllowedMethod>
    <ExposeHeader>Access-Control-Allow-Origin</ExposeHeader>
    <AllowedHeader>*</AllowedHeader>
  </CORSRule>
</CORSConfiguration>

To set up CORS for your S3 bucket:

  1. Visit https://s3.console.aws.amazon.com/s3/buckets/
  2. Click on your bucket
  3. Click "Permissions"
  4. Click "CORS configuration"

Required CORS settings for HTTP Live Streaming

Playing back HLS playlist files may require a crossdomain policy file. For convenience here you can find a working file.

Please save this to a crossdomain.xml file and store it in the root folder of your Amazon S3 Bucket or other storage location of choice.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE cross-domain-policy SYSTEM "https://www.macromedia.com/xml/dtds/cross-domain-policy.dtd">
<cross-domain-policy>
  <allow-access-from domain="*" secure="false" />
  <allow-http-request-headers-from domain="*" headers="*" />
</cross-domain-policy>

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, please use the Assembly Variable ${file.meta.relative_path} to store files in the proper paths to make the playlist files work.

Parameters

  • use

    String / Array of Strings / Object required

    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"
      ]
      

    :bulb: That’s likely all you need to know about use, but you can view advanced use cases:

    › Advanced use cases
    • Step bundling. Some Robots can gather several Step results for a single invocation. For example, the /file/compress Robot would normally create one archive for each file passed to it. If you'd set bundle_steps to true, however, it will create one archive containing all the result files from all Steps you give it. To enable bundling, provide an object like the one below to the use parameter:

      "use": {
        "steps": [
          ":original",
          "encoded",
          "resized"
        ],
        "bundle_steps": true
      }
      

      This is also a crucial parameter for the /video/adaptive Robot, otherwise you'll generate 1 playlist for each viewing quality.
      Keep in mind that all input Steps must be present in your Template. If one of them is missing (for instance it is rejected by a filter), no result is generated because the Robot waits indefinitely for all input Steps to be finished.

      Here’s a demo that showcases Step bundling.

    • Group by original. Sticking with the /file/compress Robot example, you can set group_by_original to true, in order to create a separate archive for each of your uploaded or imported files, instead of creating one archive containing all originals (or one per resulting file). This is important for for the /media/playlist Robot where you'd typically set:

      "use": {
        "steps": [
          "segmented"
        ],
        "bundle_steps": true,
        "group_by_original": true
      }
      
    • Fields. You can be more discriminatory by only using files that match a field name by setting the fields property. When this array is specified, the corresponding Step will only be executed for files submitted through one of the given field names, which correspond with the strings in the name attribute of the HTML file input field tag for instance. When using a back-end SDK, it corresponds with myFieldName1 in e.g.: $transloadit->addFile('myFieldName1', './chameleon.jpg').

      This parameter is set to true by default, meaning all fields are accepted.

      Example:

      "use": {
        "steps": [ ":original" ],
        "fields": [ "myFieldName1" ]
      }
      
    • Use as. Sometimes Robots take several inputs. For instance, the /video/merge Robot can create a slideshow from audio and images. You can map different Steps to the appropriate inputs.

      Example:

      "use": {
        "steps": [
          { "name": "audio_encoded", "as": "audio" },
          { "name": "images_resized", "as": "image" }
        ]
      }
      

      Sometimes the ordering is important, for instance, with our concat Robots. In these cases, you can add an index that starts at 1. You can also optionally filter by the multipart field name. Like in this example, where all files are coming from the same source (end-user uploads), but with different <input> names:

      Example:

      "use": {
        "steps": [
          { "name": ":original", "fields": "myFirstVideo", "as": "video_1" },
          { "name": ":original", "fields": "mySecondVideo", "as": "video_2" },
          { "name": ":original", "fields": "myThirdVideo", "as": "video_3" }
        ]
      }
      

      For times when it is not apparent where we should put the file, you can use Assembly Variables to be specific. For instance, you may want to pass a text file to the /image/resize Robot to burn the text in an image, but you are burning multiple texts, so where do we put the text file? We specify it via ${use.text_1}, to indicate the first text file that was passed.

      Example:

      "watermarked": {
        "robot": "/image/resize",
        "use"  : {
          "steps": [
            { "name": "resized", "as": "base" },
            { "name": "transcribed", "as": "text" },
          ],
        },
        "text": [
          {
            "text"  : "Hi there",
            "valign": "top",
            "align" : "left",
          },
          {
            "text"    : "From the 'transcribed' Step: ${use.text_1}",
            "valign"  : "bottom",
            "align"   : "right",
            "x_offset": 16,
            "y_offset": -10,
          }
        ]
      }
      
  • technique

    String ⋅ default: "dash"

    Determines which streaming technique should be used. Currently supports "dash" for MPEG-Dash and "hls" for HTTP Live Streaming.

  • playlist_name

    String ⋅ default: "playlist.mpd"

    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".

  • segment_duration

    Integer ⋅ 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.

FFmpeg parameters

  • ffmpeg_stack

    String ⋅ default: "v3.3.3"

    Selects the FFmpeg stack version to use for encoding. These versions reflect real FFmpeg versions.

    The current recommendation is to use "v4.3.1". Other valid values can be found here.

Demos

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