GlossaryCEA-608 / CEA-708

CEA-608 / CEA-708

CEA-608 and CEA-708 are US broadcast standards for closed captions that travel inside the video signal itself rather than in a separate file. CEA-608 is the older analog-era format with limited styling, while CEA-708 is the digital TV version with more fonts, colors and languages. In streaming, both are often carried inside HLS or DASH video so captions survive from broadcast to online.

Why it matters

Broadcast and cable content often arrives with captions already embedded as CEA-608 or 708 data. If a streaming workflow drops or garbles them, a business can fail accessibility rules and lose viewers who rely on captions, especially for live news and sports.

How it works

  1. A caption encoder inserts caption data into the video signal as it is produced or aired.
  2. CEA-608 data originally rode on line 21 of analog TV; CEA-708 carries richer data in digital video.
  3. In streaming, the caption data travels inside the video stream rather than as a separate file.
  4. Players and TVs decode the embedded data and show the captions when viewers turn them on.

What is the difference between CEA-608 and CEA-708?

CEA-608 is the older analog-era caption standard, while CEA-708 is its digital TV successor. 708 supports more languages, character sets, fonts, colors and positioning. Digital broadcasts usually carry both, with 608 data included for compatibility. Streaming players often support 608 more widely than 708's advanced styling.

CEA-608 vs WebVTT: which should I use for streaming?

Use WebVTT for on-demand streaming, and keep CEA-608/708 when captions already come embedded from a broadcast or live source. WebVTT is a separate text file that is easy to edit and translate. Embedded 608/708 travels inside the video, which suits live feeds. Many workflows convert embedded captions to WebVTT for web playback.

Where it's used

Broadcasters, live news publishers and OTT services handling cable content use CEA-608/708 to carry captions inside live and broadcast video streams through to viewers.

By the numbers

  • CTA-708 captions use a fixed 9,600 bit/s channel, typically with 960 bit/s for embedded line 21 (608) captions and 8,640 bit/s for 708 captions. (CEA-708, Wikipedia)
  • FCC rules require CTA-708 caption decoders in US digital TVs with screens 13 inches diagonal or larger. (CEA-708, Wikipedia)

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