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True 708 versus 608 captions

MacCaption is currently the world's only True CEA-708 software encoder which supports native CEA-708 features.

CEA-608 / 708 Feature Comparison Chart (PDF)

What are "708" and "608"?

CEA-608 (formerly called EIA-608) was the original closed captioning standard used for analog TV broadcasts since 1980.  This is sometimes also called "line 21" because of the way they are implemented.  Because digital technology was very limited at the time, the CEA-608 standard has many limitations and shortcomings. 

608 captions are limited to a single block character font with gray monospaced text on a black square background.  Only the standard alphanumeric and certain accented characters are supported.  Due to bandwidth restrictions, it is uncommon to see more than 2 languages encoded simultaneously.

CEA-708(also known as EIA-708) is the new closed captioning standard used for all DTV broadcasts, including both HD and SD.  708 supports a number of new features, including:

  1. 708 captions can appear in multiple fonts, sizes, colors, and styles.

    708 multiple text styles
    * simulated image

  2. 708 captions are drawn into "windows" which allows more creative and flexible positioning of the captions.

  3. 708 captions supports Unicode characters, allowing the display of Chinese, Japanese, Korean, Thai, Vietnamese, Arabic, Hebrew, and other languages and special symbols.

    708 Japanese captions

  4. 708 captions can contain up to 63 different captions tracks (although typically up to 6 are used simultaneously), without the bandwidth limitations of 608.

  5. 708 captions also include a digital form of the 608 caption data for backwards compatibility with older analog gear.

Are 708 captions only required for HD broadcasts?
708 captions are required for all captioned DTV broadcasts, which includes both HD and SD material.  The DTV transition occurred on June 11, 2009.  DTV broadcasts (with very few exemptions) must now include both 708 and 608 captions.

When submitting a captioned SD tape to a broadcaster, the 708 captions will automatically be generated from the 608 data when the video is encoded for DTV.  However, when sending a pre-encoded file for broadcast (such as a MPEG-2 transport stream), the file must contain both 708 and 608 data even if it is only SD, because it will be transmitted as-is (i.e., not re-encoded by the broadcaster).  HD tapes must always contain both 708 and 608 captions as well.

What is the difference between "True 708" captions and captions which were up-converted from 608 to 708?
Up-converted 608 captions can not take advantage of any of the new 708 caption features, such as multiple fonts and styles, multiple windows, Unicode character support, or proper support for more than 4 languages.

Do .SCC files, .CAP files, or other industry standard files contain CEA-708 caption data?
All existing industry-standard caption data formats only store CEA-608 caption data.  However, MacCaption can import any industry standard caption file format, and then up-convert the captions into CEA-708 caption data for export.

CPC has also created a new file specification called ".MCC" which contains native CEA-708 encoded caption data.  This is an open specification and free for any hardware or software manufacturer to use.  Please contact us for more information.

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