EIA-608

It was developed by the Electronic Industries Alliance and required by law to be implemented in most television receivers made in the United States.

It specifies an "Extended Data Service", which is a means for including a VCR control service with an electronic program guide for NTSC transmissions that operates on the even Line 21 field, similar to the TeleText based VPS that operates on line 16 which is used in PAL countries.

EIA-608 captions are transmitted on either the odd or even fields of Line 21 with an odd parity bit in the non-visible active video data area in NTSC broadcasts, and are also sometimes present in the picture user data in ATSC transmissions.

Raw EIA-608 caption byte pairs are becoming less prevalent as digital television replaces analog.

This layering is based on the OSI Protocol Reference Model: SDI or DVD The user data structure that follows a H.262 GOP header is as follows (the same would apply after an ISO/IEC 14496-2 GOP header): bslbf: bit string, left bit first ; uimsbf: unsigned integer, most significant bit first Caption blocks are inserted after the sequence and GOP headers, so each block is for one second of video which would end up being one or two long lines or three to four short lines of text.

Also that means if the caption_block_count is greater than 30 then the block contains both interleaved caption fields and one could devise the framing rate from the caption_block_count.

In this form, captions have to be separated into byte pairs spread over frames in one second of video rather than grouped into one block as with the DVD structure.

EIA-608 provides controls for the color of the foreground and background of the text, underlining, blinking, and italics.

As the foreground of this character is a blank space, it really means a gap in the close caption text.

[3] The only typical use in North America of this set is the use of the eighth note character to denote changes from spoken dialogue to singing or musical only scenes.

It is an acceptable broadcast engineering practice when translating EIA-608 to Teletext for PAL compatible countries to substitute this character for a number sign because of its similarity to a sharp.

TM is short for unregistered trademark and should be represented in superscript (like the Unicode character U+2122 ™ TRADE MARK SIGN).

These extended character sets are rarely used due to most European countries using the BBC Ceefax based Teletext system.

The Ceefax system is more prone to character errors due to the greater number of data bits (337 versus 16) encoded per VBI field, these errors occur either on noise prone analog transmissions or connections.

The main use has been to provide double byte code point captioning to the Japanese, Taiwanese and South Korean markets.