CEA608CEA708

CEA-608 and CEA-708 are closed captioning standards developed by the Consumer Electronics Association (now part of the Consumer Technology Association) for text captions on television. The two standards address how captions are encoded, transmitted, and rendered in different broadcasting environments. Together they are commonly referred to as CEA-608/708 closed captions, reflecting their historical and ongoing use in both analog and digital television.

CEA-608, also known as EIA-608, originated for NTSC analog television and became widely adopted in North America from the late 1980s onward. It encodes caption data in line 21 of the vertical blanking interval and provides two caption channels per field (CC1 and CC2; CC3/CC4 are optional in some implementations). The standard defines a limited character set, basic text placement, and modest styling. It is designed for compatibility with older devices, while modern digital decoders can extract and display 608 data from digital streams for backward compatibility.

CEA-708 is the digital successor introduced with ATSC broadcasts to support high-definition and advanced digital television. It expands captioning capabilities with features such as multiple caption services, multiple windows, and richer presentation options (fonts, colors, edge styles, italics), along with broader language support, including Unicode. 708 captions are delivered as data packets within digital video streams and are decoded by contemporary televisions and set-top boxes; many receivers also provide a 608 fallback path for compatibility when needed.

In practice, many HD or digital broadcasts carry 708 captions, while 608 data remains available for legacy devices or streams that require backward compatibility. The two standards together provide a bridge from legacy analog captioning to modern digital accessibility.