How to Add Audio Description to Videos
The World Wide Web Consortium (W3C), an international community that develops Web standards, lists several sufficient techniques for adding description to audio-visual material. All of these methods are reliable ways to meet the WCAG Success Criterion.
Adding a second, user-selectable soundtrack with audio descriptions.
This option is highly dependent on media player capabilities, since most devices don’t have the capacity of merging multiple sound tracks. Adding a second, user-selectable soundtrack accommodates for that by providing an option which allows users to switch the original soundtrack with a new version of the soundtrack which contains additional audio description.
Audio description focuses on key visual elements that are crucial to the comprehension of the content, such as characters and scene changes. For example, a movie file has two audio tracks, one of which includes audio description. Users can choose either one when listening to the movie by selecting the appropriate track in their media player. When using a platform that can accommodate two audio tracks to play simultaneously, a secondary audio track containing just the description is sufficient. This option is the optimal user experience because it gives the user a choice, just like closed captions.
Providing a version of a movie with audio descriptions.
This approach adds the audio description to synchronized media by utilizing a second version of the movie where the original soundtrack and additional audio description are combined into a single track.
In this case, the description is added into the original sound track during pauses in dialogue and sound effects. Although this ensures that the description doesn’t obscure original content, it limits the amount of supplementary information that can be added. An example of this method is two versions of a video of a concert are available. The first version includes solely the music, while the second version includes both the music and voice describing the actions of the performers on stage.
Providing a movie with extended audio descriptions.
This approach involves providing a second version of video content with extended audio descriptions. One of the main obstacles in creating audio description is trying to fit a vast amount of information into a very short window of time (such as during pauses in the dialogue). With extended description, however, the video can be paused to allow more time for descriptions when needed. Typically a version of the movie with extended audio descriptions and a version without descriptions are available, or the audio descriptions can be turned on and off.
Using a static text alternative to describe a talking head video.
This method is considered an alternative to audio description, and is best used for media that doesn’t have important time based information in the original video portion of the media. For example, this technique would be sufficient for “talking head” videos such as a press conference or lecture, where an individual is speaking in front of a static background and there are no important visual elements to describe. This technique is not suitable for a situation where there are several speakers, and where the identity of the speakers is not made clear in the audio track.
Using a WebVTT description track.
This method is an advisory technique, as there isn’t enough user agent support – once there is sufficient user agent support, it would be considered a sufficient technique. HTML5 video allows for the use of a WebVTT description file. This file would be included as a
<track>element with the
<type>“description.” Screen readers should be able to read this file to provide description to users. However, this functionality has very limited support across video players.
Audio Description Output Formats
Using the 3Play Media account system, you can instantly download your audio description files once they have been processed. Although audio description is required under accessibility laws, many video players and online video platforms do not support description. To alleviate any technical difficulties associated with audio description, our service will provide multiple different output formats.
Your description files will stay in your account, allowing you to access any formats anytime.
The formats provided will include:
- A time-coded WebVTT audio description track that can be read by screen readers
- A secondary MP3 or WAV audio file with synthesized speech of your description
- A secondary MP3 or WAV audio file with synthesized speech of your description and the original audio
- A secondary MP3 or WAV audio file with human voice actors reading your description*
- An MP4 video file with your streamed video, the original audio, and synthesized speech of your description
- An audio description plugin that will allow your audio description file to play with video players that don’t support multiple audio tracks or WebVTT description tracks
*Note: this option will only be available in a later release.
How to Publish Using the Audio Description Plugin
Being that most popular video players and platforms do not support WebVTT description tracks or secondary audio tracks – although there are exceptions – we provide an audio description plugin for simplicity.
Our plugin is a simple embed that references your video and plays the secondary audio description track along with your video, making it a great option for video players that don’t support audio description in a usable way. It’s also a great alternative to having to create a second version of the video with description.