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Metadata

Many files contain interesting information about their contents. This is called "metadata". Transloadit automatically extracts this metadata for all uploaded, imported, and processed files.

At the very minimum, each file will have the information such as:

{
  "id": "ae52b7f8c1b3426e8c29ea0a9daf8306",
  "name": "straw-apple.jpg",
  "basename": "straw-apple",
  "ext": "jpg",
  "size": 92230,
  "mime": "image/jpeg",
  "type": "image",
  "field": "test_file",
  "url": "http://tmp.maynard.transloadit.com/upload/1324a798a99fce7f5f8289a95a74f02b.jpg",
  "original_id": "4af24fb2595f44809f3adc2f77bc9bfa",
  "meta": { ... }
}

The information we can extract depends on the media file, its type, but also who produced it. If it was an iPhone, there's probably latitude in there for geo-positioning. More common keys include height, and duration.

To see what information we can extract from files that you will throw at us, you could try one of our demos and inspect our response after uploading a file there.

  • id
    A random and unique ID used internally by Transloadit to track the file.

  • name
    The name of the file. Transloadit will change the extension used for this field if the file undergoes processing into a different format.

  • basename
    The name of the file without the extension.

  • ext
    The extension of the file.

  • size
    The size of the file, in bytes.

  • mime
    The determined MIME type for this file.

  • type
    An abstract type describing the file, which can currently be "image", "video", "audio", or null.

  • field
    The name of the form field used to submit this file.

  • url
    The URL at which this file can be accessed. This is either a URL in your S3 bucket, or a temporary URL on our servers. Since temporary URLs expire after a few hours, you should make sure to move your files elsewhere unless you are using a storage robot.

  • original_id
    The unique ID of the original upload file from which this file was generated. This is useful to determine which file of a multi-file upload was used to generate a given file, after several Steps of processing.

  • meta
    An object containing additional metadata extracted from the file, as shown below.

Image Metadata

Although it depends on the file at hand, files whose mime type is image can typically contain data such as the following inside the meta property:

  • width
    The width of the input image, in pixels.

  • height
    The height of the input image, in pixels.

  • aspect_ratio
    The aspect ratio of the image, which is its width divided by its height. Will be 0 if for some reason the image height is 0.

  • date_recorded
    The date and time at which this image was taken, in the format YYYY/MM/DD HH:MM:SS TZ, such as "2010/06/30 22:16:06 GMT".

  • date_file_created
    The creation time for the file system.

  • date_file_modified
    The modification time for the file system.

  • title
    The title of this image, such as "Tree".

  • keywords
    An array of keywords for this image, such as ["tree", "nature"].

  • description
    A description of this image, such as "This tree is very old.".

  • location
    The location at which this image was taken, which is usually the street, such as "Zingster Str. 32".

  • creator
    The creator that took the image.

  • author
    The author that took the image. Some cameras populate this field as opposed to creator.

  • copyright
    The copyright metadata field.

  • copyright_notice
    The copyright notice metadata field.

  • city
    The city in which this image was taken, such as "Berlin".

  • state
    The state in which this image was taken, such as "Berlin".

  • country
    The country in which this image was taken, such as "Germany".

  • country_code
    The country code of the country in which this image was taken, such as "de".

  • aperture
    The aperture setting for this image, such as 5.7.

  • exposure_compensation
    The exposure compensation for this image, such as "+4/3".

  • exposure_mode
    The exposure mode for this image, such as "Auto".

  • exposure_time
    The exposure time for this image, such as "1/30".

  • flash
    The flash settings for this image, such as "Off, Did not fire".

  • focal_length
    The focal length for this image, such as "55.0 mm".

  • f_number
    The f-number for this image, such as 5.6.

  • iso
    The ISO value for this image, such as 800.

  • light_value
    The light value for this image, such as 6.9.

  • metering_mode
    The metering mode for this image, such as "Multi-segment".

  • shutter_speed
    The shutter speed for this image, such as "1/32".

  • white_balance
    The white balance setting for this image, such as "Manual".

  • device_name
    The device name of the camera, such as "iPhone 3GS".

  • device_vendor
    The camera manufacturer, such as "Apple".

  • device_software
    The version of the device software for the camera, such as "3.1.2".

  • latitude
    The latitude at which this image was taken, such as 52.5374.

  • longitude
    The longitude at which this image was taken, such as 13.4034.

  • thumbnail_index
    The index of the current thumbnail starting at 0. This key is only present for results of the /video/thumbs Robot.

  • thumbnail_offset
    The offset for the current thumbnail, in seconds. This key is only present for results of the /video/thumbs Robot.

  • frame_count
    The number of frames in an animated GIF file. This is 1 by default for all other image types.

  • colorspace
    The colorspace of the image. This could be "sRGB" or "Gray" for instance. In Transloadit's first ImageMagick stack version, there's a bug which would make the colors used in an image determine its colorspace, and a grayscale colored image would report "Gray", even if saved as "RGB".

  • has_clipping_path
    Is 1 if the image contains a clipping path, 0 otherwise.

  • average_color
    Not to be confused with dominant color, that counts a single most occurring pixel color and has limited use cases. The average color is calculated by first scaling the input image to 1 pixel.

  • has_transparency
    Returns true for images that have transparent areas. This key is only returned if you set output_meta.has_transparency to true.

  • dominant_colors
    Returns an array of the 20 most used colors for images. This key is only returned if you set output_meta.dominant_colors to true.

Video Metadata

Although it depends on the file at hand, files whose mime type is video can typically contain data such as the following inside the meta property:

  • width
    The width of the video, in pixels. If the video was meant to be displayed with a different display ratio than the pixel ratio, this indicates the width at which the video is to be displayed.

  • height
    The height of the video, in pixels.

  • framerate
    The frame rate of the video, such as 29.5.

  • video_bitrate
    The video bit rate of the video, such as 500000.

  • video_codec
    The video codec of the video, such as "ffh264".

  • audio_bitrate
    The audio bit rate of the video, such as 128000.

  • audio_samplerate
    The audio sample rate of the video, such as 44100.

  • audio_channels
    The number of audio channels in the video, such as 2.

  • audio_codec
    The audio codec of the video, such as "faad".

  • seekable
    Whether the format of the video supports seeking, such as true.

  • colorspace
    The colorspace of the video. This could be "sRGB" or "Gray" for instance. This key is only returned if you set output_meta.colorspace to true.

  • date_recorded
    For details, see the description for image metadata.

  • date_file_created
    For details, see the description for image metadata.

  • date_file_modified
    For details, see the description for image metadata.

  • device_name
    For details, see the description for image metadata.

  • device_vendor
    For details, see the description for image metadata.

  • device_software
    For details, see the description for image metadata.

  • latitude
    For details, see the description for image metadata.

  • longitude
    For details, see the description for image metadata.

Audio Metadata

Although it depends on the file at hand, files whose mime type is audio can typically contain data such as the following inside the meta property:

  • duration
    The length of the audio file in seconds.

  • audio_bitrate
    Bits per second (for all channels combined).

  • audio_samplerate
    The audio sample rate in herz, such as 44100, for a CD.

  • audio_channels
    Number of channels. Typically 2, for stereo.

  • audio_codec
    The Audio codec used. Here's a list of all audio codecs that Transloadit supports.

  • artist
    Many applications that produce audio write additional information into the audio file such as artist, year, album, genre.

  • mean_volume
    The mean volume of the audio file. This key is only returned if you set output_meta.mean_volume to true.

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