Kaltura - Managing the labels of caption files for media in Kaltura MediaSpace

When captions are added to media in Kaltura MediaSpace, there is a need to distinguish between a) captions that were auto-generated by Kaltura's machine captioning process, and b) captions that have gone through a more intensive creation or editing process, resulting in a much more accurate final product. This document explains the strategy and process for properly labelling and maintaining caption files for Kaltura media objects, on the UW-Madison campus.

On the UW-Madison campus, there are two ways of creating captions for media files in Kaltura MediaSpace:

  1. Automatically, using Kaltura's "machine captioning" service. This process employs voice-recognition technology to transcribe recorded speech. It is commonly considered to be only 75% accurate. (If your captions were generated with this automated process, we strongly encourage you to edit those captions to ensure or improve their accuracy. Instructions on editing captions are available in Kaltura - How to edit captions in Kaltura MediaSpace.)
  2. Manually -- This process may begin with a machine captioned file (mentioned above) or a text file, containing the script that was used during the creation of the video. Either way, those captions are then edited for accuracy and clarity. (This is a time-consuming and labor-intensive process, and is often performed by a professional for-fee service.)

A need has been identified to help end-users and media owners distinguish between caption files that were generated automatically, and those that have been manually edited for accuracy.

The best way to make that distinction is by managing the "label" of the caption file. This label is what appears when the end-user selects the CC button on a video in Kaltura MediaSpace. In the image below, "English" is the label for the English captions file.


Effective February 24, 2021, the suffix of "(auto-generated)" is appended to the label of all machine-generated captions. This suffix informs viewers and media owners that the captions were automatically generated by Kaltura's machine captioning process, and have not been edited.

For all machine captions generated prior to February 24, 2021 -- which have not, yet, been edited for accuracy -- we recommend you edit the label and manually add the suffix "(auto-generated)".

Once an auto-generated caption file has been edited for accuracy, we recommended you remove that suffix from the label.

To edit the label for a captions file, log into Kaltura MediaSpace, and locate the media file in question: 

  1. Click the Actions drop-down menu and select Edit:
    A screenshot showing the user having clicked the Actions drop-down menu. The cursor hovers over the "Edit" option which is outlined in orange.

  2. Click the Captions tab.

  3. Locate the caption file you wish to make available to the end user, and click the Edit (the pencil) icon. (That is the icon on the far-right.)
  4. The resulting pop-up window has three editable fields.
    1. Language - this was the language chosen during the ordering of machine captions.
    2. Accuracy - after editing your captions, this setting can be placed at 100%
    3. Label - this is the name of the caption file, as it appears within the CC button (on the video player).

  5. When finished making the desired edits, click Save.

Other Icons to Manage the Captions File


  1. The remaining "Actions" buttons are described here.
    • Screenshot showing the "Set as Default" icon which looks like a check-mark in the "Captions" tab of the "Edit" window. Set as Default - Set this caption as the default caption for a video.
    • Screenshot showing the "Delete" icon which looks like a X in the "Captions" tab of the "Edit" window. Delete - Delete this caption from your media.
    • Screenshot showing the "Download" icon which looks like an arrow pointing down into a computer in the "Captions" tab of the "Edit" window. Download - Download the caption file in .SRT format.
    • Screenshot showing the "Show On Player" icon which looks like a monitor with a line through it in the "Captions" tab of the "Edit" window.Show on Player/Don't Show on Player - Cause this caption to "Show" (or "Don't Show") in the CC button, on the video player. (This button is a toggle: "on" or "off".)