The Difference Between 608 and 708 Captions
CEA stands for Consumer Electronics Association. EIA stands for Electronic Industries Alliance, the group which first developed the standard for captions.
The EIA is no longer in operation, but CEA (one of its branches) is still active.
Currently, two standards of closed captioning exist for broadcast television – 608 closed captions were the old captioning standard for analog television, while 708 closed captions are the new captioning standard for the modern digital television.
With the 2009 DTV Delay Act passed in the United States, digital television officially replaced analog television and most closed captions began to transition over from 608 to 708. However, in an effort to make this transition smoother, digital television maintained the ability to support 608 captioning.
Regardless, 708 captions are preferable and are today considered standard by the Federal Communications Commission (FCC).
What Are 608 Closed Captions?
CEA-608 (Line 21) captions used to be the standard for analog broadcast television. While they have mainly been replaced by 708 captions, it is still possible for 608 captions to be embedded in digital television. You may recognize them by their stereotypical appearance: black box backgrounds with all uppercase white text.
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608 captions are encoded in the Line 21 data area of the analog TV signal (hence the name) and are only viewable with a decoder.
Line 21 has two fields – usually, English captions are transmitted in the first field and Spanish captions (or occasionally, captions meant for children) are transmitted in the second field.
While digital TV supports 608 captions in its picture user data (which was meant to make the transition from analog easier), 608 captions do not support any of the appearance options offered by 708 captioning and additionally do not comply with many of the FCC’s current closed captioning requirements.
Due to character limitations, 608 captions are limited to encoding in English, Spanish, French, Portuguese, Italian, German, & Dutch. The two fields available in Line 21 allow for only two language options at a time.
608 captions have a fixed position on the screen. Note that this is not compliant with the FCC’s quality standards, introduced in February of 2014.
What Are 708 Closed Captions?
CEA-708 captions were introduced for use with digital television, and follow much more advanced standards than 608 captions. These captions offer significant user control over caption appearance, allowing the viewer to select from 8 font options, 3 text sizes, 64 text colors, and 64 background colors. Additionally, 708 captions offer options for background opacity and dropshadowed (or edged) text.
These customizable options mean that 708 captions are more accessible to individual viewers with unique requirements & preferences – for example, a person who is colorblind may prefer to change the text and background colors to create higher contrast. The only appearance-related quality of 708 captioning that a user cannot control is whether they roll-up or pop-on, because of the fact that the two methods must be formatted differently.
While it is possible to transmit older 608 captions on digital television, it is not possible to stream newer 708 captions on analog television.
708 captions are funneled through MPEG-2 streams in the picture user data of digital television. Initially, captions are transmitted in picture order and must be rearranged like picture frames, otherwise known as the DTVCC transport stream.
Contrary to 608, the newer 708 captions come with a complete library of special characters & symbols, and are designed to support any alphabet in the world. Furthermore, the way in which 708 captions are transmitted allows for multiple tracks to be included in one program – as a result, this multilingual capacity makes programming more accessible for a global audience.
Considering that the FCC’s quality standards state captions should not block other important on-screen information, 708 captions include the ability to be repositioned in order to comply. By comparison, the on-screen positioning of 608 captions cannot be changed by individual users.
608 Captions vs. 708 Captions
Overall, CEA-708 captions are an improved captioning standard, with more options for appearance, placement, and languages.
CEA-608 (Line 21) vs. CEA-708 captions
|Standard for analog television||Standard for digital television|
|Can be transmitted on analog & digital television||Can only be transmitted on digital television|
|Appearance: uppercase white text on black box background||Appearance: user-controlled options include 8 fonts in 3 sizes, 64 text colors, 64 background colors, varying background opacity, and edged/dropshadowed text|
|Supports only 2 languages at a time||Supports multilingual captions|
|Language options are limited to English, Spanish, French, Portuguese, Italian, German, and Dutch (due to lack of special characters)||Supports captions in any language (characters & symbols from every alphabet are supported)|
|Transmitted on Line 21||Embedded in MPEG-2 streams|
|Caption position is fixed.||Caption position can be changed. The FCC requires that captions be repositioned if they obscure important visual information.|
The Future of 608 vs. 708 Closed Captions
Although CEA-608 captions may still appear on digital televisions, this format is outdated and no longer compliant with most of the FCC’s guidance on closed captioning standards. Many modern-day captioning standards for broadcast television and online video are now based on CEA-708 captions, most notably due to advanced user control requirements.
This post was originally published in October 2014 as Closed Captioning for Broadcast Television: What’s the Difference Between 708 Captions and 608 (Line 21) Captions?, and has since been updated for accuracy, clarity, and freshness.
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