Captions, Transcripts and Descriptors
Multimedia are content objects that use two or more formats (audio, video, slide shows, text, graphic animations, interactive and/or synchronized element etc.) to deliver information. They use a media player (Quicktime, RealMedia, Window’s Media Player, Flash Player etc.) to access the information. The players can be an embedded plug-in to the HTML page or a standalone application accessed from the web page.
Embedded media players use click and point activities for controls and are generally not accessible to assistive technology like screen readers. Standalone media players provide keyboard access to the controls and menus, are accessible to assistive technology and recommended for multimedia delivery..
Section 508 requires that audio, visual and video content has an alternative equivalent that conveys all relevant information needed for understanding of content being presented.
Alternative Equivalents
- Text transcripts are written equivalents of the audio track. This includes dialogue and environmental sounds relevant to convey the information. These are created as text files that can be synchronized with a movie (video/audio) to create the captions and subtitles.
- Subtitles are synchronized text alternatives for the spoken word. They can be a translation or just written equivalent of the dialogue.
- Captions are synchronized text equivalents of the audio track of a multimedia presentation. The transcript must be by synchronized with the audio/video tract. Captions can be either:
- Closed – captions are hidden in the video signal and need a special decoder (Line 21 on a television) and can be controlled by the viewer
- Open – captions are decoded and visible on the video image. On the web, multimedia presentations are viewed using a client-side media player.
- Text descriptors: written descriptions of graphic and video content
- Collated text transcripts: captions with text descriptors
- Audio descriptors: spoken descriptions of video /graphic content. These are created by providing audio annotations or synchronizing the narration track with the video track. Information on creating audio description
- Real time captions: simultaneous written equivalents of the spoken word. These do not have to be verbatim, but as close as possible to convey the meaning. They are used for live meetings and the caption is displayed in a text editor or sent to a text window, or an encoder to be inserted into the video signal or video caption reader
Recommended Alternatives
- Audio only: text transcript
- Video /Visual Only: text /audio descriptor
- Multimedia: collated text transcripts (captions, text descriptor)
It is recommed that a text transcript in addition to captions be provided to serve the deaf-blind visitor.
Beyond serving the needs of individuals with hearing and visual impairments, alternative equivalents supplement the audio/visual information for everyone, deliver information to alternative devices, make it available for printing, serves people with language and reading limitations as well as make it available to search engines.
Creating a Text Transcript (text files)
- From a script created prior to development of the multimedia presentation.
- Manually typed from the audio file.
- Using voice recognition technology like DragonDictate or ViaVoice either by the speaker or by someone "shadowing" the speakers words into a voice recognition system trained to their voice.
- Using a thrid party transcription services like eScriptionist.com, Casting Words or Enablr. Depending on number of speakers and turn around time, the price at these services ranges between $0.75 to $2.25 an audio minute.
Creating Captions and Subtitles
Steps for inserting creating captions or subtitles into the multimedia presentation
- Create or obtain a text transcript
- Chunk text into caption blocks and add speaker names. A block consists of 1 to 2 lines about 40 characters in lenght. Optimum block is single line with 8 - 10 words. Save file as a text (.txt) file.
- Create a Caption Text file. Use tools like NCAM MAGPie 2 , HiCaption , or external services like CaptionSync to apply the time code to the text chunks synchronized with audio/video track and save the file in the format used by the Media Player (.smi, .rt, .qt, .fla etc)
- Integrate caption text file with the multimedia presentation. Use a metafile like ASX (Windows Media Player) or SMIL (RealMedia or QuickTime Media Player) to create the integrated captioned media file.
