Closed-Captioning Description - Sanyo AVM-2550S Training Manual

The VB7C chassis provides for the decoding and displaying the latest Closed-
Captioning information transmitted with many of today's television broadcasts.
Captioning is a printed version of the program sound or other information
displayed on the screen. Television stations and Cable companies control
which programs are broadcast with these services. At the present, there are
two types of Closed-Captions in use, Captions and Text.
Captions
Captions are video related information and are normally one or two lines, but
can be up to four lines, appearing anywhere on the screen. They can be
displayed as roll-up, pop-on, or paint-on.
information is displayed in two, three or four consecutive rows. Data appears
in the bottom row and scrolls up as new information is received. In the pop-
on mode, two memories are used. One memory is displayed while the other
is receiving new data. When the proper command is received the memories
are swapped, causing the complete caption to appear at once. In the paint-
on mode, the characters are displayed as they are received, one column at a
time from left to right.

CLOSED-CAPTIONING DESCRIPTION

In the roll-up mode, caption
Text
Text is non-video related information and is displayed in a black box which
overwrites the screen. In a full screen Text mode the box is 15 rows high and
34 columns wide. The rows may contain a maximum of 32 characters. When
all 15 rows have been used, the display scrolls up as additional data is
received.
Channels
The closed-caption system provides for four different data channels. The are;
Captions-Language l (C1), Captions-Language ll (C 2), Text-Language l (T1),
and Text-Language ll (T2). Both languages can be English, Spanish or any
other language in either case.
The complete captioning information, including location, color, characters,
commands, channel etc., is transmitted using an encoded composite data
signal sent on Line 21, field one of the TV signal.
The caption data on Line 21 consists of a seven cycle sine-wave clock run-in
burst, a start bit and two bytes of data. Each byte is an 8 bit alphanumeric
character based on the USA Standard Code for Information Interchange
(USASCll) with odd parity. Additional codes have been added for foreign
characters and special symbols. The Clock rate is .5035 MHz (32 fH).
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