click here to skip directly to page content
Media Access Group  Versión en español
About Us Services and Products Research and Development Resources Get Involved

A wealth of information for producers, broadcasters, distributors, exhibitors, consumers, parents, and educators.


TechFacts: Information about captioning for video professionals

Volume 5 - Set-top vs. Built-in Decoders: Remaining Compatible as New Captioning Features are Introduced

Broadcasters may receive calls from caption consumers about incorrect letters in captions or mission captions. This issue of TechFacts explains briefly why some set-top decoders are now displaying flawed captions and introduces you to the new features available thanks to built-in decoders in most new televisions sold since mid-1993.

The Television Decoder Act of 1990, which requires built-in decoder circuitry in most new television receivers, charged the FCC with developing standards for the new decoders. The FCC turned to the Electronic Industries Association (EIA) to determine the caption features that could be implemented and how decoders could be improved.

During an EIA-suggested transition period, all new features need to be backward compatible to work with the set-top decoders sold since 1980. As a result, features such as new placement options and an extended character set are being phased in gradually.

In the meantime, captioning has never been more visible. The EIA estimates more than 20 million new televisions with built-in decoders are sold each year. That means every home in America will have a least one decoder-equipped television by 2000.

Set-top Decoders - Background
The original caption decoders, the TeleCaption I, went on sale in 1980. These models were sold as stand-alone decoders or were built into television sets marketed by Sears. In 1985, the National Captioning Institute introduced the next-generation decoder, the TeleCaption II. This same basic decoder design was also used in subsequent set-top models TeleCaption 3000, TeleCaption 4000 and TeleCaption VR 100.

Estimates indicate that, at best, set-top decoder sales reached about 350,000. There was a large disparity between the number of decoders sold and the potential audience for captioning-22 million deaf and hard-of-hearing viewers. Many viewers who could benefit from captioning did not buy a decoder due to lack of awareness of the service, prohibitive cost or the difficulty of installation. These factors, combined with the potential educational benefits of captioning for millions of children and adults struggling with literacy or learning English as a second language, prompted Congress to pass the Television Decoder Circuitry Act in 1990.

Current Decoder Standards: FCC Requirements vs. EIA Recommendations
There are two standards which are often referred to when speaking about decoders. "FCC compliant" refers to rules called "FCC Report and Order FCC 91-119 and FCC Memorandum, Opinion and Order FCC 92-157." This is the basic standard for caption decoders; it was published by the FCC in response to the Television Decoder Circuitry Act. "EIA 608 compliant" refers to the document "EIA 608: Recommended Practice for Line 21 Data Service." EIA 608 is a recommendation published by the EIA outlining several optional features and services such as XDS (see volume 3 of TechFacts for more information about these services). However, it is a recommended practice, not a requirement, for receiver manufacturers or caption providers to implement these capabilities.

FCC public reports can be obtained through
2100 M. Street, N.W.
Suite 140
Washington, D.C. 20037
202 857-3800
(There are minimal report retrieval and per page copy fees)

A copy of EIA-608 is available from the EIA for $106. Contact:
Electronic Industries Association
Engineering Department
2001 Pennsylvania Avenue, N.W.
Washington, D.C. 20006
202 457-4900

Several companies still manufacture set-top decoders. Since the FCC only regulates receivers, these decoders are not necessarily EIA 608 compliant or even FCC compliant. This means they might not respond correctly to new features. The Caption Center regularly tests new set-top decoders to determine if they are compatible with the new features. For a list of professional or consumer-grade decoder manufacturers, contact The Caption Center.

Older set-top decoders - limitations
Older set-top decoders aren't compatible with many of the features outlined in the FCC rules. The EIA proposed a transition schedule for phasing in the various new caption features. All caption providers should adhere to this schedule. The Telecaption I decoder (pre-1985) will be the first to become obsolete.

Caption agencies will be sending special compatibility codes for the TeleCaption II (TC 3000, 4000 and VR 100). These decoders, however, won't be able to display relocatable roll up or mid-screen placement (see below). In 2002 these compatibility codes will be phased out, and the TeleCaption II generation will no longer function correctly.

New Features

Captioning in six colors-cyan, yellow, green, magenta, red and blue-has been a part of the basic decoder specification from the beginning (1980). However, no set-top decoder that we know of has ever implemented this feature. Codes for color captions do not adversely affect older decoders; all the captions simply display as white text on a black background. (Receivers with built-in Telecaption I decoders marketed by Sears in the early '80s were able to display color captions, although, very few of these units are still in service.)

Almost all modern receivers containing FCC-compliant decoders implement the color feature. Caption text may be white or in one of the seven colors, as determined by the caption service provider. The color of the background (usually black) is determined by the receiver manufacturer.

Paint On Style
The TeleCaption II generation of decoders included some new features that were incompatible with the original TeleCaption I. The most important of these is paint-on style. When the TeleCaption I decoder receives paint-on style, it stops working. That is, it ignores the paint-on caption and displays no caption at all. It remains in this state until it receives a pop-on or roll-up caption, which are the most common type of captions.

Expanded Character Set and Transparent Space
Also added in 1985 were eleven new characters (Ç, Ñ, º, à, è, â, ê, î, ô, û, and the transparent space) which do not display correctly on the TeleCaption I. These characters do not cause the TeleCaption I to stop working; they just appear as incorrect characters. Of these, the most interesting is the transparent space, which appears as a forward slash (/) on the TeleCaption I. The transparent space allows for more accurate horizontal positioning (better centering) on 1985 and later decoders.

In mid-1994, caption service providers began using features that were not completely compatible with the TeleCaption I. Since January 1, 1995, EIA 608 has recommended full support of TeleCaption II (post-1985 models) features, including the eleven new characters (above) and paint-on style.

1/4, 3/4, ® and TM
The EIA recommends that caption-service providers continue to avoid the characters 1/4, 3/4, ® and TM. That is because the TeleCaption I and TeleCaption II decoders display 1/4 and 3/4 characters in response to special codes, while FCC-compliant decoders display ® and TM characters in response to those same codes. Since we expect TeleCaption II decoders to be in widespread use for several more years, there is no way to guarantee these characters will display correctly. It is recommended that the use of ® and TM not take place until 2002, the phase-out date for the TeleCaption II generation.

Mid-Screen Placement
The EIA has recommended use of "PACs for rows 5-11 with default PAC" as of January, 1995. A PAC is a Preamble Address Code, the command that precedes each row of captioning to tell the decoder where on the screen to begin that row. The TeleCaption I and TeleCaption II decoders recognized PACs for rows 1-4 (top third of the screen) and 12-15 (bottom third). In 1991, the FCC added PACs for the middle of the screen, rows 5-11. The TeleCaption I reacts to these new PACs in much the same way as to paint-on style: it will not display the caption. The TeleCaption II, however, simply ignores the new PACs. For this reason, it is theoretically possible to send dual PACs at the beginning of each row: one old-style PAC for the TeleCaption II and one new-style PAC for an FCC-compliant decoder. The result is a missing caption on a TeleCaption I, a caption in the top or bottom third on the TeleCaption II, and a caption in the middle of the screen on an FCC-compliant decoder.

Relocatable Roll Up
The FCC mandates that new decoders have a feature we call "relocatable roll-up." This is simply the ability of the caption-service provider to move a roll-up caption to other parts of the screen. Previously roll-up captions were restricted to bottom-third display only. Since roll-up captions are used primarily for real-time (or live) captioning such as news, captions would often cover important information such as speaker identification.

On TeleCaption I and TeleCaption II decoders, relocatable roll-up captions default to the bottom of the screen. As long as the caption-service provider restricts itself to the old PACs (for rows 1-4 and 12-15) and follows certain other rules, relocatable roll up has no effect on TeleCaption I and TeleCaption II decoders. That is, you can relocate the roll-up caption on an FCC-compliant decoder while leaving it at the bottom on all other decoders.

The Caption Center was the first to use this feature. During the 1994 Olympics, captions were bumped to the top of the screen to avoid covering athlete's names, scores and times which were often displayed at the bottom of the screen.

If you have questions about captioning, or know a colleague who would like to receive TechFacts, please let us know:

The Caption Center
125 Western Avenue
Boston, MA 02134
(617) 300-3600 V/TTY
(617) 300-1020 fax

Caption Services Description Services NCAM