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True 708 versus 608 captions
MacCaption is currently the
world's only
True CEA-708 software encoder
which supports all CEA-708 features.
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:
-
708 captions can appear in multiple fonts,
sizes, colors, and styles.

* simulated image |
-
708 captions are drawn into "windows" which
allows more creative and flexible positioning of the captions.
-
708 captions supports Unicode characters,
allowing the display of Chinese, Japanese, Korean, Thai,
Vietnamese, Arabic, Hebrew, and other languages and special
symbols.
-
708 captions can contain up to 63 different
captions tracks (although typically up to 6 are used
simultaneously), without the bandwidth limitations of 608.
-
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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