Closed Captioning - DVDs, BDs, & HD DVDs

DVDs, BDs, & HD DVDs

NTSC DVDs may carry closed captions in data packets of the MPEG-2 video streams inside of the Video-TS folder. Once played out of the analog outputs of a set top DVD player, the caption data is converted to the Line 21 format. They are sent to the TV by the player and can be displayed with a TV's built-in decoder or a set-top decoder as usual. When viewed on a personal computer, caption data can be viewed by software that can read and decode the caption data packets in the MPEG-2 streams of the DVD-Video disc. Windows Media Player (before Windows 7) in Vista supported only closed caption channels 1 and 2 (not 3 or 4). And Apple's DVD Player does not have the ability to read and decode Line 21 caption data which is recorded on a DVD made from an over-the-air broadcast. Apple's DVD Player can display some movie DVD captions.

In addition to Line 21 closed captions, video DVDs may also carry subtitles as a bitmap overlay which can be turned on and off via a set top DVD player or DVD player software, just like captions. This type of captioning is usually carried in a subtitle track labeled either "English for the hearing impaired" or, more recently, "SDH" (Subtitled for the Deaf and Hard of hearing). Many popular Hollywood DVD-Videos can carry both subtitles and closed captions (see Stepmom DVD by Columbia Pictures). On some DVDs, the Line 21 captions may contain the same text as the subtitles; on others, only the Line 21 captions include the additional non-speech information (even sometimes song lyrics) needed for deaf and hard of hearing viewers. European Region 2 DVDs do not carry Line 21 captions, and instead list the subtitle languages available—English is often listed twice, one as the representation of the dialogue alone, and a second subtitle set which carries additional information for the deaf and hard of hearing audience. (Many deaf/HOH subtitle files on DVDs are reworkings of original teletext subtitle files.)

HD DVD and Blu-ray disc media cannot carry Line 21 closed captioning due to the design of High-Definition Multimedia Interface (HDMI) specifications that were designed to replace older analog and digital standards, such as VGA, S-Video, and DVI. Both Blu-ray disc and HD DVD can use either PNG bitmap subtitles or 'advanced subtitles' to carry SDH type subtitling, the latter being an XML based textual format which includes font, styling and positioning information as well as a unicode representation of the text. Advanced subtitling can also include additional media accessibility features such as "descriptive audio".