Video captioning

Captioning video for universal access

The amount of and ease of access to video materials has increased dramatically in the past several years. It is easier than ever for instructors as well as students to use video online in teaching and learning activities.

video illustrating closed captioning

Although most instructors may be aware that the Americans with Disabilities Act (ADA) spells out requirements for accessibility, they may not know the specifics as they apply to the use of video and multimedia in their courses. Section 508 is an amendment to the Rehabilitation Act that requires federal agencies and programs that receive federal funding (including ISU) to make their electronic and information technology accessible to people with disabilities.

If you use videos in your classes -- or for student recruiting or providing important information on a website at ISU -- you'll need to add captions (aka subtitles) to meet the requirements of Section 508. Following are some guidelines and information to help ensure your videos are accessible to all.

Types of captioning

There are three basic types of captions: hard, pre-rendered, and soft.

  • Hard captions are "burned in" to the video. They cannot be turned off.
  • Pre-rendered captions are most commonly used on delivery media such as DVDs or Blu-ray. They may be superimposed over the video during playback, offer a choice of languages, and can be toggled on or off. If you present professionally produced videos on DVD or Blu-ray in class, be sure to use equipment that can display closed captions.
  • In a university setting, where videos are most likely to be either delivered online or played in class from a computer, soft captions are the primary option. Soft captions are rendered during video playback from an external file that consists of the caption text and timing codes. They may be turned on or off and can be superimposed directly over the video or in an adjacent panel. Soft captions can be created and associated with an existing video.

Creating captions

There are two major tasks involved in captioning a video:

  1. Creating a transcript of the audio -- including identification of who is speaking and describing other relevant sounds, and
  2. Specifying precise timing for every bit of text so it is synchronized with the video.

Transcribing may be done in any of several ways. A contracted transcriptionist may be hired. To learn more about this option at ISU, contact Student Disability Resources. Or a student assistant may be assigned the task.

Once a transcript is created, it needs to be synchronized with the video. Currently, CaptionTube can be used to caption YouTube videos, or stand-alone applications, such as Jubler can be used to coordinate each section of a transcript with the appropriate point in a video.

Video-hosting services, YouTube and Vimeo offer automatic captioning services using speech-to-text converters to create caption files that in most instances need significant editing before they are ready. The amount of editing depends to a large degree on the quality of the audio and the clarity of the dialogue. But the resulting file will include timing codes that can serve as rough guidelines for you to determine how to break the text into appropriate segments.