EIA-608, also known as line 21 captions, used to be the standard for closed captioning for NTSC

NTSC

NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...

 TV broadcast

Broadcasting

Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...

s in the United States and Canada. It also specifies Extended Data Service, a means for including information such as program name in a television transmission.

It was developed by the Electronic Industries Alliance

Electronic Industries Alliance

The Electronic Industries Alliance was a standards and trade organization composed as an alliance of trade associations for electronics manufacturers in the United States. They developed standards to ensure the equipment of different manufacturers was compatible and interchangeable...

 and required by law to be implemented in most television receivers made in the United States.

EIA-608 captions are transmitted on line 21 in the non-visible active video data area in NTSC broadcasts, and are also sometimes present in the picture user data in ATSC transmissions. It uses a fixed bandwidth of 960 bit/s.

EIA-608 is becoming less prevalent as digital television

Digital television

Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...

 replaces analog. ATSC broadcasts use the EIA-708

EIA-708

CEA-708 is the standard for closed captioning for ATSC digital television streams in the United States and Canada. It was developed by the Electronic Industries Alliance.Unlike most DVB captions, CEA-708 captions are textual like traditional Line 21 captions...

 caption protocol, which is fully capable of representing Spanish and French, and mostly able to display other Western Europe

Western Europe

Western Europe is a loose term for the collection of countries in the western most region of the European continents, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a geographic entity—the region lying in the...

an language

Language

Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

s. EIA-708

EIA-708

CEA-708 is the standard for closed captioning for ATSC digital television streams in the United States and Canada. It was developed by the Electronic Industries Alliance.Unlike most DVB captions, CEA-708 captions are textual like traditional Line 21 captions...

 also supports the carriage of EIA-608 compatible captions inside ancillary data channels.

Channels

EIA-608 defines four channels of caption information, so that a program could, for example have captions in four different languages. There are two channels, called 1 and 2 by the standard, in each of the two fields of a frame. However, the channels are often presented to users numbered simply 1-4.

Within each channel, there are two streams of information which might be considered subchannels: one carries "captions" and the other "text." The latter is not in common use.

Extended Data Service

The EIA-608 data stream format includes Extended Data Service (XDS), a variety of information about the transmission. It is all optional, and can include:

• channel name
• channel call letters
• program name
• offensiveness rating (violence, sex, etc.)
• program category (drama, game show, etc.)

Characters

There are three sets of characters that the EIA-608 stream can direct the receiver to display: basic characters, special characters, and extended characters. A single two-byte EIA-608 command (represented by a single VBI line) can specify two basic characters, one special character, or one extended character.

Extended characters are a later addition to the standard and their decoding is optional.

EIA-608 provides controls for the color of the foreground and background of the text, underlining, blinking, and italics. The default color scheme is white characters on a black background, all opaque.

The Transparent Space special character implies a transparent background even in the absence of any background control commands. As the foreground of this character is a blank space, it really means a gap in the close caption text.

Basic Characters

A command with Bits 13 or 14 on directs the receiver to display two basic characters at the current cursor position for the current mode (closed caption or text). Each character is a code point
(identifies the character to display) as follows. The code is almost identical to ASCII; the exceptions are shown in red.

Binary Decimal Hex Graphic 0010 0000 32 20 (SP) Space (punctuation) In writing, a space is a blank area devoid of content, serving to separate words, letters, numbers, and punctuation. Conventions for interword and intersentence spaces vary among languages, and in some cases the spacing rules are quite complex.... 0010 0001 33 21 ! Exclamation mark The exclamation mark, exclamation point, or bang, or "dembanger" is a punctuation mark usually used after an interjection or exclamation to indicate strong feelings or high volume , and often marks the end of a sentence. Example: “Watch out!” The character is encoded in Unicode at... 0010 0010 34 22 " 0010 0011 35 23 # Number sign Number sign is a name for the symbol #, which is used for a variety of purposes including, in some countries, the designation of a number... 0010 0100 36 24 $ 0010 0101 37 25 % 0010 0110 38 26 & Ampersand An ampersand is a logogram representing the conjunction word "and". The symbol is a ligature of the letters in et, Latin for "and".-Etymology:... 0010 0111 39 27 ' 0010 1000 40 28 ( 0010 1001 41 29 ) 0010 1010 42 2A á 0010 1011 43 2B + 0010 1100 44 2C , Comma (punctuation) The comma is a punctuation mark. It has the same shape as an apostrophe or single closing quotation mark in many typefaces, but it differs from them in being placed on the baseline of the text. Some typefaces render it as a small line, slightly curved or straight but inclined from the vertical, or... 0010 1101 45 2D - Hyphen The hyphen is a punctuation mark used to join words and to separate syllables of a single word. The use of hyphens is called hyphenation. The hyphen should not be confused with dashes , which are longer and have different uses, or with the minus sign which is also longer... 0010 1110 46 2E . Full stop A full stop is the punctuation mark commonly placed at the end of sentences. In American English, the term used for this punctuation is period. In the 21st century, it is often also called a dot by young people... 0010 1111 47 2F / Slash (punctuation) The slash is a sign used as a punctuation mark and for various other purposes. It is now often called a forward slash , and many other alternative names.-History:... 0011 0000 48 30 0 0011 0001 49 31 1 0011 0010 50 32 2 0011 0011 51 33 3 0011 0100 52 34 4 0011 0101 53 35 5 0011 0110 54 36 6 0011 0111 55 37 7 0011 1000 56 38 8 0011 1001 57 39 9 0011 1010 58 3A : Colon (punctuation) The colon is a punctuation mark consisting of two equally sized dots centered on the same vertical line.-Usage:A colon informs the reader that what follows the mark proves, explains, or lists elements of what preceded the mark.... 0011 1011 59 3B ; Semicolon The semicolon is a punctuation mark with several uses. The Italian printer Aldus Manutius the Elder established the practice of using the semicolon to separate words of opposed meaning and to indicate interdependent statements. "The first printed semicolon was the work of ... Aldus Manutius"... 0011 1100 60 3C < 0011 1101 61 3D = 0011 1110 62 3E > 0011 1111 63 3F ? Question mark The question mark , is a punctuation mark that replaces the full stop at the end of an interrogative sentence in English and many other languages. The question mark is not used for indirect questions...

Binary Decimal Hex Graphic 0100 0000 64 40 @ 0100 0001 65 41 A 0100 0010 66 42 B 0100 0011 67 43 C 0100 0100 68 44 D 0100 0101 69 45 E 0100 0110 70 46 F 0100 0111 71 47 G 0100 1000 72 48 H 0100 1001 73 49 I 0100 1010 74 4A J 0100 1011 75 4B K 0100 1100 76 4C L 0100 1101 77 4D M 0100 1110 78 4E N 0100 1111 79 4F O 0101 0000 80 50 P 0101 0001 81 51 Q 0101 0010 82 52 R 0101 0011 83 53 S 0101 0100 84 54 T 0101 0101 85 55 U 0101 0110 86 56 V 0101 0111 87 57 W 0101 1000 88 58 X 0101 1001 89 59 Y 0101 1010 90 5A Z 0101 1011 91 5B [ 0101 1100 92 5C é 0101 1101 93 5D ] 0101 1110 94 5E í 0101 1111 95 5F ó

Binary Decimal Hex Graphic 0110 0000 96 60 ú 0110 0001 97 61 a 0110 0010 98 62 b 0110 0011 99 63 c 0110 0100 100 64 d 0110 0101 101 65 e 0110 0110 102 66 f 0110 0111 103 67 g 0110 1000 104 68 h 0110 1001 105 69 i 0110 1010 106 6A j 0110 1011 107 6B k 0110 1100 108 6C l 0110 1101 109 6D m 0110 1110 110 6E n 0110 1111 111 6F o 0111 0000 112 70 p 0111 0001 113 71 q 0111 0010 114 72 r 0111 0011 115 73 s 0111 0100 116 74 t 0111 0101 117 75 u 0111 0110 118 76 v 0111 0111 119 77 w 0111 1000 120 78 x 0111 1001 121 79 y 0111 1010 122 7A z 0111 1011 123 7B ç 0111 1100 124 7C ÷ 0111 1101 125 7D Ñ 0111 1110 126 7E ñ 0111 1111 127 7F SB

In the table above, SB represents a solid block.

Special Characters

A command to display a special character has a first byte of 0x11 or 0x19 (depending upon channel). The second byte is a code point in the range 0x30-0x3F as follows.

Binary Decimal Hex Graphic 0011 0000 48 30 ® 0011 0001 49 31 ° 0011 0010 50 32 ½ 0011 0011 51 33 ¿ 0011 0100 52 34 ™ 0011 0101 53 35 ¢ 0011 0110 54 36 £ 0011 0111 55 37 ♪ 0011 1000 56 38 à 0011 1001 57 39 TS 0011 1010 58 3A è 0011 1011 59 3B â 0011 1100 60 3C ê 0011 1101 61 3D î 0011 1110 62 3E ô 0011 1111 63 3F û

TM is short for unregistered trademark and should be represented in superscript (™). TS in the table above represents a "transparent space" or non-breaking space

Non-breaking space

In computer-based text processing and digital typesetting, a non-breaking space or no-break space is a variant of the space character that prevents an automatic line break at its position. In certain formats , it also prevents the “collapsing” of multiple consecutive whitespace characters into a...

. Finally, the musical note (♪) is used to denote singing

Singing

Singing is the act of producing musical sounds with the voice, and augments regular speech by the use of both tonality and rhythm. One who sings is called a singer or vocalist. Singers perform music known as songs that can be sung either with or without accompaniment by musical instruments...

 or background music in captions.

Extended Characters

A command to display an extended character has Bits 12, 9, and 5 on and Bits 11, 10, and 6 off. The code point for the character consists of Bits 8 and 4-0.

There are 64 possible extended character code points, but not all are used. These characters are accented other letters not found in the basic and special character sets.

Control Commands

Bits 15 and 7 are always odd parity bits. Bit 11 is always the channel bit.

For a preamble address code these are as follows: Bits 15 and 7 are parity bits. Bits 14 and 13 are always 0, bits 12 and 6 are always 1. Bits 10, 9, 8 and 5 indicate the row position. Bits 4, 3, 2 and 1 indicate the attribute of the text. Bit 0 indicates underline.

The row bits specify which of the 15 screen rows should contain the caption text: row 11 (0000), 1 (0010), 2 (0011), 3, 4, 12, 13, 14, 15, 5, 6, 7, 8, 9, or 10 (1111).

The attributes bits allow 16 possibilities, which are: white (0000), green, blue, cyan, red, yellow, magenta, italics, indent 0, indent 4, indent 8, indent 12, indent 16, indent 20, indent 24, indent 28 (1111).

For a midrow code these are as follows: Bits 14, 13, 10, 9, 6 and 4 are always 0, bits 12, 8 and 5 are always 1. Bits 3, 2 and 1 form the color attribute (see the listing of attributes). Bit 0 indicates underline.

For other control codes these are as follows: Bits 14, 13, 9, 6 and 4 are always 0, bits 12, 10 and 5 are always 1. Bit 8 chooses between line 21 and 284. Bits 3, 2, 1 and 0 identify the particular action.

The command bits allow 16 possibilities, which are: resume caption loading (0000), backspace (0001), delete to end of row (0100), roll-up captions 2-rows, roll-up captions 3 rows, roll-up captions 4-rows, flash on (0.25 seconds once per second), resume direct captioning, text restart, resume text display, erase displayed memory, carriage return, erase nondisplayed memory, end of caption (1111).

For tabs these are as follows: Bits 14, 13, 6, 4, 3, 2 are always 0, bits 12, 10, 9, 8, 5 are always 1. Bits 1 and 0 determine the number of tab offsets.

External links

• Closed caption decoder requirements for analog television receivers - 47 C.F.R. 15.119 - From the F.C.C.
  Federal Communications Commission
  The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
  
  
• Index of requirements documents in text and PDF for 47 C.F.R. 15 - use the 119 link - From the F.C.C.
  Federal Communications Commission
  The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...