CaptionSync produces Audio Description output file formats, called "side-car" files, to use with video players that support audio description. These audio description files can also be used with the Smart Player feature for requests made via List of URLs or an integration that creates lists (such as Kaltura or Brightcove Video Cloud).
There are several output files generated for audio description results:
- .ad.vtt: Contains the text of the descriptions and their start times in the industry standard WebVTT format.
- .ad.txt: Contains both the captions and the descriptions for the video, interleaved based on the timeline of the video. This is known as a Full-Text Alternative file in WCAG terms, and is similar to a screenplay for the video.
- .html: An HTML version of the Full-Text Alternative
- .mp3: Contains the descriptions, synthesized using TTS, concatenated together. We call this an audio sprite.
- .sm.txt: This is a manifest for the audio sprite in JSON format, containing the start times and durations for each description.
- .mp4 (additional cost output): This output is called Open Audio Description, and is generated by splicing the descriptions into the original video, extending the timeline of the video. Descriptions are "burned into" the video, with a freeze frame at each description.
- .ad.srt (included with Open AD): This is a caption file that corresponds to the extended timeline of the Open AD MP4.
The typical format generated for an Audio Description request is a "side-car" file (.ad.vtt) that is picked up by players that support audio description. Most video players do not yet support audio description, but our Smart Player is a good tool to play audio description for your online media in a seamless way, particularly with video you don't own.
The Smart Player allows the audio description file to play while pausing the original audio, then resume once the description is complete in a hassle-free manner. More complete descriptions can be included than with traditional audio description, because there is no need to constrain the descriptions to gaps in the dialog (this technique of pausing the video to insert longer descriptions is known as Extended Audio Description). The audio description file is associated locally with the media file and you just need to share the URL to the player with your audience. It also provides a number of enhancements over regular players, like an interactive transcript, speed buttons, the ability to toggle audio description ON and OFF, along with the displaying of captions, among others. Watch a sample of a Smart Player displaying Audio Description results. More information is available in our Smart Player Tutorial.
The side-car file is the typical format generated for audio description requests, where the file contains timing information as well as the description of the video content. This file is picked up at play time by players that support audio description, such as the Able Player. You can also associate this file with the video in regular players, for example, on YouTube, and then use a screen reader to listen to the description. We have a tutorial where we describe how to associate an .ad.vtt file with a YouTube video, to listen to the results using a screen reader.
Note that the side-car file you receive from us is an audio description WebVTT file, and that different players and platforms have different requirements when it comes to playing the audio description files.
- Depending on the type of video content you submit for an audio description request, you may receive either a full audio description or a static descriptive text. Both are provided in the WebVTT format.
- For videos where a single person is talking against an unchanging background, and where there is no relevant visual information that requires a full audio description, Static Descriptive Text results are generated instead.
- The Smart Player URL can be generated from Describe -> Status of Audio Description, if one was not already created. Both the Audio Description and Captioning results need to be completed for the Generate link to show.
- On some releases/configurations of Windows 10, the Audio Description voiceover on the Smart Player may not be played on Firefox. The Audio Description voiceover is contained in an MP3 file, and support for this format is not built directly into Firefox. Instead it relies on support from the OS, in this case, Windows 10. In some releases/configurations of Windows 10, that support may not be available, preventing the Audio Description voiceover from playing on Firefox.