Joe Clark: Media access

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See also: Finer points in DVD accessibility capabilities

Updated 2002.04.16

Basic DVD accessibility capabilities

On this page:
DefinitionsBasic issuesClosed vs. openCapabilities (with sexy table) ¶ The best?

Finer points in DVD accessibility capabilities
DVDs with audio description
Listings: Region 1, Region 2

DVD is potentially the most accessible audiovisual format yet created. What can you do with DVD that you can’t do with videotapes or oldschool laserdiscs? Find out right here in these pages.

Defining our terms

A fuller explanation is available, but let’s start small with some very general definitions of the Big Four access techniques.

Closed captions
Transcriptions (usually for deaf/hard-of-hearing viewers) that you can turn on or off.
Open captions
Captions that are always visible.
Written translations. Can be closed or open.
Spoken translations. Can be closed or open.
Audio description
Narration (usually for blind/visually-impaired viewers). Can be closed or open.

Now some technical definitions (see also Gary Robson’s Caption FAQ):

Line 21
Closed-captioning system used in North America and other NTSC countries. So named because the caption codes are transmitted on the 21st line of the TV picture. Line 21 caption-decoding chips are built into nearly all U.S. and Canadian TV sets (and some other devices).
Line 22
Variation of the North American system used in PAL countries. Technically, captions are transmitted on Line 25, but that corresponds to Line 22 on an NTSC set. You generally need a set-top or external decoder to watch Line 22 captions.
Television standard (listing; map) used in the U.S., Canada, Japan, and a few other countries. Incompatible with PAL and SÉCAM.
Television standard used in the U.K., Europe, Australia, and elsewhere. Incompatible with NTSC.
Television standard used in France and a very few other places; not all that different from PAL, but just different enough to be incompatible with PAL-only devices. Incompatible with NTSC.
World System Teletext
Longstanding system for transmitting teletext pages and captioning used in PAL and SÉCAM. Usually, your TV set or VCR decodes teletext and World System Teletext data for you.
Oldschool 12″ videodiscs (see FAQ).
Laserdisc Graphics format. Little-used outside Japan. Subtitles are encoded as an audio band; apparently up to 16 streams were available. (2002.04.16)
Subtitles for the deaf and hard-of-hearing” (SDH)
Used exclusively with DVDs, “SDH” use the subtitling mechanism of DVDs for captioning. Titles move around, notate sound effects, and do everything else that captions do even though you watch them via the so-called subtitle apparatus of your DVD and player, neither of which knows the difference between a subtitle and a caption; it is purely an issue of putting visible words to different uses that a human being can tell apart.
Region 1
DVD region (see FAQ) for Canada, the U.S., and U.S. territories.

Basic issues

As ever in audiovisual works, deaf people can’t hear the audio, blind people can’t see the video, and viewers, whether disabled or not, may not understand the source language.

Closed vs. open

You can include access features such that they can be turned off (closed); though that terminology has usually been reserved for captions, it applies to any of the Big Four.

Open accessibility is what viewers tend to be accustomed to in the fields of subtitling, dubbing, and audio description. You cannot turn such features off. In fact, it is somewhat strange to be able to turn those three features on and off; really, DVD is the first technology that made that possible.

Every format – videotape, laserdisc, and DVD – can carry open features. An interplay between closed and open features is much more common than people think: Some films may contain passages in a second language that are open-subtitled in the film’s main language; the disc or tape may nonetheless contain captions or subtitles or dubbing tracks or descriptions. Or you might be watching the dubbed version of a film (an open feature) that also carries closed captions.


Given that all formats can handle open accessibility features, just what can videotapes, laserdiscs, and DVDs do in the realm of closed features?

Can carry Line 21 or Line 22 closed captions.
  1. Can carry Line 21 or (theoretically) Line 22 closed captions, though they never do the latter. (Line 22 was invented too late; laserdiscs were already going out of style in favour of DVDs.)
  2. PAL discs can carry World System Teletext captions and sometimes did (examples).
  3. Can carry LD+G subtitles and very occasionally did.
  4. NTSC laserdiscs have a second audio track of poor quality that can (theoretically) carry dubbing or description, though they never do.
Offers 32 subtitle streams and eight audio tracks, plus Line 21 closed captions in Region 1 discs only.

You may be wondering: If DVDs can carry closed captions, why bother captioning a DVD using the subtitling capacity (so-called SDH)? Closed captions don’t work on computers, old TVs without decoder chips, or indeed any device without a decoder, whereas SDH works on any DVD player. Also, closed captions work only on Region 1 discs. It is often desirable to have both closed captions and SDH, for reasons I won’t bore you with here.

The capabilities of the various formats are summarized as follows:

Closed access features of video formats
Access technique DVD Laserdisc Videotape
Region 1 Elsewhere NTSC PAL
Line 21 closed captions Yes N/A Yes Yes No
Line 22 closed captions N/A No No N/A Yes
World System Teletext closed captions N/A No Yes N/A No
Subtitles Yes: From 32 streams Yes: From 32 streams Yes: 16 streams No No
“Subtitles for the deaf and hard-of-hearing” Yes: From 32 streams Yes: From 32 streams No No No
Dubbing Yes: Seven streams (plus main language) Yes: Seven streams (plus main language) Yes, in theory No No

(Or you can load this table in a new document for printing.)

Notable details: In Europe, Australia, the U.K., and the like, it is theoretically possible to store closed World System Teletext captions on a videotape. It’s just that you can’t do it with an ordinary VHS tape. Super-VHS, yes. Professional formats, yes. But not ordinary VHS. Similarly, some teletext VCRs can record World System Teletext captions onto VHS tapes, but typically only that make and model of VCR can play them back. That’s why the entire Line 22 system was imported. Even with Line 22, though, it is tremendously difficult to record a captioned program off the air and watch the captions on playback.

So are DVDs the best?

DVDs can carry far more access features than any other format, but a few problems remain.

To make a DVD fully accessible, then, you need so-called subtitles for the deaf and hard-of-hearing (and optional Line 21 closed captions); subtitling and dubbing in selected languages; and audio description. Most commercial DVDs on the market in Region 1 have some combination of the first three access features; commercial DVDs in other regions almost always have subtitling and dubbing and, occasionally, subtitles for the deaf and hard-of-hearing. Described DVDs are rare – there are fewer than 20 in existence.

Change history

Added information about teletext and Laserdisc Graphics on, predictably enough, laserdiscs.
Fixed some dumb-arse mistakes.
Transformed main page into a backgrounder.
Added a couple of more Shouldas.
Added The Grinch
Added Final Fantasy to MoPix shouldas. Fixed Star Wars listing.
Corrected a raft of mistakes and made miscellaneous additions.
Updated discussion of language codes.
After finding life too short to look up all the previously-described Hollywood movies without description on DVD, I did it anyway.

Now that you’re an expert, care to read a bit more? Other pages available: