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Our /audio/encode Robot

Encode audio

🤖/audio/encode converts audio files into all kinds of formats for you. We provide encoding presets for the most common formats.

Usage example

Encode uploaded audio to MP3 format at a 256 kbps bitrate:

  "steps": {
    "mp3_encoded": {
      "robot": "/audio/encode",
      "use": ":original",
      "preset": "mp3",
      "bitrate": 256000,
      "ffmpeg_stack": "v6.0.0"


  • 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": [

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

  • output_meta

    Object / Boolean ⋅ default: {}

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

    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.

  • preset

    String ⋅ default: "mp3"

    Performs conversion using pre-configured settings.

    If you specify your own FFmpeg parameters using the Robot's ffmpeg parameter and you have not specified a preset, then the default mp3 preset is not applied. This is to prevent you from having to override each of the mp3 preset's values manually.

    For a list of audio presets, see audio presets.

  • bitrate

    Integer ⋅ default: auto [?]

    Bit rate of the resulting audio file, in bits per second. If not specified will default to the bit rate of the input audio file.

  • sample_rate

    Integer ⋅ default: auto [?]

    Sample rate of the resulting audio file, in Hertz. If not specified will default to the sample rate of the input audio file.

FFmpeg parameters

  • ffmpeg_stack

    String ⋅ default: "v5.0.0"

    Selects the FFmpeg stack version to use for encoding. These versions reflect real FFmpeg versions. We currently recommend to use "v6.0.0".

    Supported values: "v5.0.0", "v6.0.0".

    A full comparison of video presets, per stack, can be found here.

  • ffmpeg

    Object ⋅ default: {}

    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.

HLS Parameters

This Robot used to support HLS parameters, but we now recommend using our specialized 🤖/video/adaptive instead.


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