Merge video, audio, images into one video

🤖/video/merge composes a new video by adding an audio track to existing still image(s) or video.

Parameters

• 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 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"
      ]
    }
    

  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

  v5 | v6 | v7 | 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".

• 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 | 195 more ↓

  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.

• resize_strategy

  crop | fit | fillcrop | min_fit | pad | stretch (default: "pad")

  If the given width/height parameters are bigger than the input image's dimensions, then the resize_strategy determines how the image will be resized to match the provided width/height. See the available resize strategies.

• background

  string (default: "#00000000")

  The background color of the resulting video the "rrggbbaa" format (red, green, blue, alpha) when used with the "pad" resize strategy. The default color is black.

• framerate

  string | number | string (default: "1/5")

  When merging images to generate a video this is the input framerate. A value of "1/5" means each image is given 5 seconds before the next frame appears (the inverse of a framerate of "5"). Likewise for "1/10", "1/20", etc. A value of "5" means there are 5 frames per second.

• image_durations

  Array<string | number> (default: [])

  When merging images to generate a video this allows you to define how long (in seconds) each image will be shown inside of the video. So if you pass 3 images and define [2.4, 5.6, 9] the first image will be shown for 2.4s, the second image for 5.6s and the last one for 9s. The duration parameter will automatically be set to the sum of the image_durations, so 17 in our example. It can still be overwritten, though, in which case the last image will be shown until the defined duration is reached.

• duration

  string | number (default: 5)

  When merging images to generate a video or when merging audio and video this is the desired target duration in seconds. The float value can take one decimal digit. If you want all images to be displayed exactly once, then you can set the duration according to this formula: duration = numberOfImages / framerate. This also works for the inverse framerate values like 1/5.

  If you set this value to null (default), then the duration of the input audio file will be used when merging images with an audio file.

  When merging audio files and video files, the duration of the longest video or audio file is used by default.

• audio_delay

  string | number (default: 0)

  When merging a video and an audio file, and when merging images and an audio file to generate a video, this is the desired delay in seconds for the audio file to start playing. Imagine you merge a video file without sound and an audio file, but you wish the audio to start playing after 5 seconds and not immediately, then this is the parameter to use.

• loop

  boolean (default: false)

  Determines whether the shorter media file should be looped to match the duration of the longer one. For example, if you merge a 1-minute video with a 3-minute audio file and enable this option, the video will play three times in a row to match the audio length.

• replace_audio

  boolean (default: false)

  Determines whether the audio of the video should be replaced with a provided audio file.

• vstack

  boolean (default: false)

  Stacks the input media vertically. All streams need to have the same pixel format and width - so consider using a /video/encode Step before using this parameter to enforce this.

• image_url

  string

  The URL of an image to be merged with the audio or video. When this parameter is provided, the robot will download the image from the URL and merge it with the other media.

• transition

  none | crossfade | fade_to_black (default: "none")

  The type of transition effect to apply between concatenated video clips. Only applies when concatenating multiple videos (using video_1, video_2, etc. or pre_roll/post_roll inputs).

  • "none" — No transition effect. Videos are joined end-to-end.
  • "crossfade" — A gradual blend from one clip to the next (both video and audio).
  • "fade_to_black" — The current clip fades out to black, then the next clip fades in from black.

• transition_duration

  string | number (default: 1)

  The duration of the transition effect in seconds. Only applies when transition is not "none". Supports float values (e.g., 0.5 for a 500ms transition) and must be greater than 0 whenever transitions are enabled. The applied transition is automatically capped at half of the shorter clip in each transition pair to prevent overlapping transitions.

Demos

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