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OVERVIEW
Models 8084/8084AD/8085 Closed Caption Encoder Manual
ITU:
The United Nations regulatory body governing all forms of
communications. ITU-R (previously CCIR) regulates the radio
frequency spectrum, while ITU-T (previously CCITT) deals with
the telecommunications standards.
ITU-R601: (This document previously known as CCIR-601).
international standard for component digital television from
which was derived SMPTE 125M and EBU 3246-E standards.
ITU-R601 defines the sampling systems, matrix values and filter
characteristics for both Y, B-Y, R-Y and RGB component digital
television signals.
ITU-R656 (This document previously known as CCIR-656). The physical
parallel
and
ITU-R656 defines the parallel connector pinouts as well as the
blanking, sync and multiplexing schemes used in both parallel
and serial interfaces. It reflects definitions found in EBU Tech
3267 (for 625 line systems) and SMPTE 125M (parallel 525 line
systems) and SMPTE 259M (serial 525 line systems).
JULIAN DATE: The Julian day number is a count of days elapsed since
Greenwich mean noon on January 1, 4713B.C. January 1st,
1993 was JD 2448989; January 1st, 2000 was JD 2451545.
MODIFIED JULIAN DATE (MJD): The Modified Julian Date is a
continuous count of the number of days elapsed since 17
November 1858. It is often more useful than conventional
calendar dates for record keeping over long periods of time,
since the MJD's of two events can easily be subtracted to
determine the time difference in days. Usually, the MJD is
specified as a number with 5 significant digits. As an example,
the MJD for 1 January 1995 is 49718, meaning that this many
days have elapsed between 17 November 1858 and 1 January
1995.
The Modified Julian date is calculated by subtracting
2400000.5 days from the Julian Date. Thus the Modified Julian
Day 1 begins at Greenwich midnight.
LINEAR TIME CODE (LTC): A digital code used for timing and control
purposes on video tape and associated audio tape machines. It
is recorded on a longitudinal track with audio characteristics and
is referred to as LTC (Sometimes this code is also referred to
as longitudinal code or SMPTE). Each 80 bit code word is
associated with one television frame, and consists of 26 time
bits, 6 flag bits, 32 user bits and 16 sync bits. Date information
may optionally encoded into the user bits. This code is often
used for distribution time of day information to station clock
displays and automation systems.
defines LTC.
PAC:
Stands for Preamble Address Code. These codes are
embedded into the line 21 caption data. They define the caption
Revision 1.6.6
serial
interconnect
scheme
The SMPTE 12M standard
An
for
ITU-R601.
Page 1-10
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