Sec. 15.119 Closed caption decoder requirements for television
receivers.
(a) Effective July 1, 1993, all TV broadcast receivers with picture
screens 33 cm (13 in) or larger in diameter shipped in interstate
commerce, manufactured, assembled, or imported from any foreign country
into the United States shall comply with the provisions of this section.
Note: This paragraph places no restriction on the shipping or sale
of television receivers that were manufactured before July 1, 1993.
(b) Transmission format. Closed-caption information is transmitted
on line 21 of field 1 of the vertical blanking interval of television
signals, in accordance with Sec. 73.682(a)(22) of this chapter.
(c) Operating modes. The television receiver will employ customer-
selectable modes of operation for TV and Caption. A third mode of
operation, Text, may be included on an optional basis. The Caption and
Text Modes may contain data in either of two operating channels,
referred to in this document as C1 and C2. The television receiver must
decode both C1 and C2 captioning, and must display the captioning for
whichever channel the user selects. The TV Mode of operation allows the
video to be viewed in its original form. The Caption and Text Modes
define one or more areas (called ``boxes'') on the screen within which
caption or text characters are displayed.
Note: For more information regarding Text mode, see ``Television
Captioning for the Deaf: Signal and Display Specifications'',
Engineering Report No. E-7709-C, Public Broadcasting Service, dated May
1980, and ``TeleCaption II Decoder Module Performance Specification'',
National Captioning Institute, Inc., dated November 1985. These
documents are available, respectively, from the Public Broadcasting
Service, 1320 Braddock Place, Alexandria, VA 22314 and from the National
Captioning Institute, Inc., 5203 Leesburg Pike, Falls Church, VA 22041.
(d) Screen format. The display area for captioning and text shall
fall approximately within the safe caption area as defined in paragraph
(n)(12) of this section. This display area will be further divided into
15 character rows of equal height and 32 columns of equal width, to
provide accurate placement of text on the screen. Vertically, the
display area begins on line 43 and is 195 lines high, ending on line 237
on an interlaced display. All captioning and text shall fall within
these established columns and rows. The characters must be displayed
clearly separated from the video over which they are placed. In
addition, the user must have the capability to select a black background
over which the captioned letters are displaced.
(1) Caption mode. In the Caption Mode, text can appear on up to 4
rows simultaneously anywhere on the screen within the defined display
area. In addition, a solid space equal to one column width may be placed
before the first character and after the last character of each row to
enhance legibility. The caption area will be transparent anywhere that
either:
(i) No standard space character or other character has been
addressed and no accompanying solid space is needed; or,
(ii) An accompanying solid space is used and a ``transparent space''
special character has been addressed which does not immediately precede
or follow a displayed character.
(2) [Reserved]
(e) Presentation format. In analyzing the presentation of
characters, it is convenient to think in terms of a non-visible cursor
which marks the screen position at which the next event in a given mode
and data channel will occur. The receiver remembers the cursor position
for each mode even when data are received for a different address in an
alternate mode or data channel.
(1) Screen addressing. Two kinds of control codes are used to move
the cursor to specific screen locations. In Caption Mode, these
addressing codes will affect both row and column positioning. In Text
Mode, the codes affect only column positioning. In both modes, the
addressing codes are optional. Default positions are defined for each
mode and style when no addressing code is provided.
(i) The first type of addressing code is the Preamble Address Code
(PAC). It assigns a row number and one of eight ``indent'' figures. Each
successive indent moves the cursor four columns to the right (starting
from the left margin). Thus, an indent of 0 places the
[[Page 641]]
cursor at Column 1, an indent of 4 sets it at Column 5, etc. The PAC
indent is non-destructive to displayable characters. It will not affect
the display to the left of the new cursor position on the indicated row.
Note that Preamble Address Codes also set initial attributes for the
displayable characters which follow. See paragraph (h) of this section
and the Preamble Address Code table.
(ii) The second type of addressing code is the Tab Offset, which is
one of three Miscellaneous Control Codes. Tab Offset will move the
cursor one, two, or three columns to the right. The character cells
skipped over will be unaffected; displayable characters in these cells,
if any, will remain intact while empty cells will remain empty, in the
same manner that a PAC indent is non-destructive.
(2) [Reserved]
(f) Caption Mode. There are three styles of presenting text in
Caption Mode: roll-up, pop-on, and paint-on. Character display varies
significantly with the style used, but certain rules of character
erasure are common to all styles. A character can be erased by
addressing another character to the same screen location or by
backspacing over the character from a subsequent location on the same
row. The entire displayed memory will be erased instantly by receipt of
an Erase Displayed Memory command. Both displayed memory and non-
displayed memory will be entirely erased simultaneously by either: The
user switching receiver channels or data channels (C1/C2) or fields (F1/
F2) in decoders so equipped; the loss of valid data (see paragraph (j)
of this section); or selecting non-captioning receiver functions which
use the display memory of the decoder. Receipt of an End of Caption
command will cause a displayed caption to become non-displayed (and vice
versa) without being erased from memory. Changing the receiver to a non-
captioning mode which does not require use of the decoder's display
memory will leave that memory intact, and the decoder will continue to
process data as if the caption display were selected.
(1) Roll-up. Roll-up style captioning is initiated by receipt of one
of three Miscellaneous Control Codes that determine the maximum number
of rows displayed simultaneously, either 2, 3 or 4 contiguous rows.
These are the three Roll-Up Caption commands.
(i) The bottom row of the display is known as the ``base row''. The
cursor always remains on the base row. Rows of text roll upwards into
the contiguous rows immediately above the base row to create a
``window'' 2 to 4 rows high.
(ii) The Roll-Up command, in normal practice, will be followed (not
necessarily immediately) by a Preamble Address Code indicating the base
row and the horizontal indent position. If no Preamble Address Code is
received, the base row will default to Row 15 or, if a roll-up caption
is currently displayed, to the same base row last received, and the
cursor will be placed at Column 1. If the Preamble Address Code received
contains a different base row than that of a currently displayed
caption, the entire window will move intact (and without erasing) to the
new base row immediately.
(iii) Each time a Carriage Return is received, the text in the top
row of the window is erased from memory and from the display or scrolled
off the top of the window. The remaining rows of text are each rolled up
into the next highest row in the window, leaving the base row blank and
ready to accept new text. This roll-up must appear smooth to the user,
and must take no more than 0.433 second to complete. The cursor is
automatically placed at Column 1 (pending receipt of a Preamble Address
Code).
(iv) Increasing or decreasing the number of roll-up rows instantly
changes the size of the active display window, appropriately turning on
or off the display of the top one or two rows. A row which is turned off
should also be erased from memory.
(v) Characters are always displayed immediately when received by the
receiver. Once the cursor reaches the 32nd column position on any row,
all subsequent characters received prior to a Carriage Return, Preamble
Address Code, or Backspace will be displayed in that column replacing
any previous character occupying that address.
(vi) The cursor moves automatically one column to the right after
each
[[Page 642]]
character or Mid-Row Code received. A Backspace will move the cursor one
column to the left, erasing the character or Mid-Row Code occupying that
location. (A Backspace received when the cursor is in Column 1 will be
ignored.)
(vii) The Delete to End of Row command will erase from memory any
characters or control codes starting at the current cursor location and
in all columns to its right on the same row. If no displayable
characters remain on the row after the Delete to End of Row is acted
upon, the solid space (if any) for that row should also be erased to
conform with the following provisions.
(viii) If a solid space is used for legibility, it should appear
when the first displayable character (not a transparent space) or Mid-
Row Code is received on a row, not when the Preamble Address Code, if
any, is given. A row on which there are no displayable characters or
Mid-Row Codes will not display a solid space, even when rolled up
between two rows which do display a solid space.
(ix) If the reception of data for a row is interrupted by data for
the alternate data channel or for Text Mode, the display of caption text
will resume from the same cursor position if a Roll-Up Caption command
is received and no Preamble Address Code is given which would move the
cursor.
(x) A roll-up caption remains displayed until one of the standard
caption erasure techniques is applied. Receipt of a Resume Caption
Loading command (for pop-on style) or a Resume Direct Captioning command
(for paint-on style) will not affect a roll-up display. Receipt of a
Roll-Up Caption command will cause any pop-on or paint-on caption to be
erased from displayed memory and non-displayed memory.
(2) Pop-on. Pop-on style captioning is initiated by receipt of a
Resume Caption Loading command. Subsequent data are loaded into a non-
displayed memory and held there until an End of Caption command is
received, at which point the non-displayed memory becomes the displayed
memory and vice versa. (This process is often referred to as ``flipping
memories'' and does not automatically erase memory.) An End of Caption
command forces the receiver into pop-on style if no Resume Caption
Loading command has been received which would do so. The display will be
capable of 4 full rows, not necessarily contiguous, simultaneous
anywhere on the screen.
(i) Preamble Address Codes can be used to move the cursor around the
screen in random order to place captions on Rows 1 to 15. Carriage
Returns have no effect on cursor location during caption loading.
(ii) The cursor moves automatically one column to the right after
each character or Mid-Row Code received. Receipt of a Backspace will
move the cursor one column to the left, erasing the character or Mid-Row
Code occupying that location. (A Backspace received when the cursor is
in Column 1 will be ignored.) Once the cursor reaches the 32nd column
position on any row, all subsequent characters received prior to a
Backspace, an End of Caption, or a Preamble Address Code, will replace
any previous character at that location.
(iii) The Delete to End of Row command will erase from memory any
characters or control codes starting at the current cursor location and
in all columns to its right on the same row. If no displayable
characters remain on a row after the Delete to End of Row is acted upon,
the solid space (if any) for that element should also be erased.
(iv) If data reception is interrupted during caption loading by data
for the alternate caption channel or for Text Mode, caption loading will
resume at the same cursor position if a Resume Caption Loading command
is received and no Preamble Address Code is given that would move the
cursor.
(v) Characters remain in non-displayed memory until an End of
Caption command flips memories. The caption will be erased without being
displayed upon receipt of an Erase Non-Displayed Memory command, a Roll-
Up Caption command, or if the user switches receiver channels, data
channels or fields, or upon the loss of valid data (see paragraph (j) of
this section).
(vi) A pop-on caption, once displayed, remains displayed until one
of the standard caption erasure techniques is
[[Page 643]]
applied or until a Roll-Up Caption command is received. Characters
within a displayed pop-on caption will be replaced by receipt of the
Resume Direct Captioning command and paint-on style techniques (see
below).
(3) Paint-on. Paint-on style captioning is initiated by receipt of a
Resume Direct Captioning command. Subsequent data are addressed
immediately to displayed memory without need for an End of Caption
command.
(i) Preamble Address Codes can be used to move the cursor around the
screen in random order to display captions on Rows 1 to 15. Carriage
Returns have no affect on cursor location during direct captioning. The
cursor moves automatically one column to the right after each character
or Mid-Row Code is received. Receipt of a Backspace will move the cursor
one column to the left, erasing the character or Mid-Row Code occupying
that location. (A Backspace received when the cursor is in Column 1 will
be ignored.) Once the cursor reaches the 32nd column position on any
row, all subsequent characters received prior to a Preamble Address Code
or Backspace will be displayed in that column replacing any previous
character occupying that location.
(ii) The Delete to End of Row command will erase from memory any
characters or control codes starting at the current cursor location and
in all columns to its right on the same row. If no displayable
characters remain on the row after the Delete to End of Row is acted
upon, the solid space (if any) for that element should also be erased.
(iii) If the reception of data is interrupted during the direct
captioning by data for the alternate caption channel or for Text Mode,
the display of caption text will resume at the same cursor position if a
Resume Direct Captioning command is received and no Preamble Address
Code is given which would move the cursor.
(iv) Characters remain displayed until one of the standard caption
erasure techniques is applied or until a Roll-Up Caption command is
received. An End of Caption command leaves a paint-on caption fully
intact in non-displayed memory. In other words, a paint-on style caption
behaves precisely like a pop-on style caption which has been displayed.
(g) Character format. Characters are to be displayed on the screen
within a character ``cell'' which is the height and width of a single
row and column. The following codes define the displayable character
set. Television receivers manufactured prior to January 1, 1996 and
having a character resolution of 5 x 7 dots, or less, may display the
allowable alternate characters in the character table. A statement must
be in a prominent location on the box or other package in which the
receiver is to be marketed, and information must be in the owner's
manual, indicating the receiver displays closed captioning in upper case
only.
Character Set Table
Special Characters
These require two bytes for each symbol. Each hex code as shown will
be preceded by a 11h for data channel 1 or by a 19h for data channel 2.
For example: 19h 37h will place a musical note in data channel 2.
------------------------------------------------------------------------
HEX Example Alternate Description
------------------------------------------------------------------------
30. TM See note\1
\ Trademark symbol
35. cents Cents sign
36. TM. It is left to each individual manufacturer to interpret
these symbols in any way that meets the legal needs of the user.
Standard characters
------------------------------------------------------------------------
HEX Example Alternate Description
------------------------------------------------------------------------
20. Standard space
21. ! Exclamation mark
22. `` Quotation mark
23. Pounds (number) sign
24. $ Dollar sign
25. % Percentage sign
[[Page 644]]
26. & Ampersand
27. ' Apostrophe
28. ( Open parentheses
29. ) Close parentheses
2A. a A Lower-case a with acute accent
2B. + Plus sign
2C. , Comma
2D. - Minus (hyphen) sign
2E. . Period
2F. / Slash
30. 0 Zero
31. 1 One
32. 2 Two
33. 3 Three
34. 4 Four
35. 5 Five
36. 6 Six
37. 7 Seven
38. 8 Eight
39. 9 Nine
3A. : Colon
3B. ; Semi-colon
3C. < Less than sign
3D. = Equal sign
3E. > Greater than sign
3F. ? Question mark
40. @ At sign
41. A Upper-case A
42. B Upper-case B
43. C Upper-case C
44. D Upper-case D
45. E Upper-case E
46. F Upper-case F
47. G Upper-case G
48. H Upper-case H
49. I Upper-case I
4A. J Upper-case J
4B. K Upper-case K
4C. L Upper-case L
4D. M Upper-case M
4E. N Upper-case N
4F. O Upper-case O
50. P Upper-case P
51. Q Upper-case Q
52. R Upper-case R
53. S Upper-case S
54. T Upper-case T
55. U Upper-case U
56. V Upper-case V
57. W Upper-case W
58. X Upper-case X
59. Y Upper-case Y
5A. Z Upper-case Z
5B. [ Open bracket
5C. e E Lower-case e with acute accent
5D. ] Close bracket
5E. i I Lower-case i with acute accent
5F. o O Lower-case o with acute accent
60. u U Lower-case u with acute accent
61. a A Lower-case a
62. b B Lower-case b
63. c C Lower-case c
64. d D Lower-case d
65. e E Lower-case e
66. f F Lower-case f
67. g G Lower-case g
68. h H Lower-case h
69. i I Lower-case i
6A. j J Lower-case j
6B. k K Lower-case k
6C. l L Lower-case l
6D. m M Lower-case m
6E. n N Lower-case n
6F. o O Lower-case o
70. p P Lower-case p
71. q Q Lower-case q
72. r R Lower-case r
73. s S Lower-case s
74. t T Lower-case t
75. u U Lower-case u
76. v V Lower-case v
77. w W Lower-case w
78. x X Lower-case x
79. y Y Lower-case y
7A. z Z Lower-case z
7B. c C Lower-case c with cedilla
7C. Division sign
7D. N Upper-case N with tilde
7E. n N Lower-case n with tilde
7F. Solid block
------------------------------------------------------------------------
(h) Character Attributes--(1) Transmission of Attributes. A
character may be transmitted with any or all of four attributes: Color,
italics, underline, and flash. All of these attributes are set by
control codes included in the received data. An attribute will remain in
effect until changed by another control code or until the end of the row
is reached. Each row begins with a control code which sets the color and
underline attributes. (White non-underlined is the default display
attribute if no Preamble Address Code is received before the first
character on an empty row.) Attributes are not affected by transparent
spaces within a row.
(i) All Mid-Row Codes and the Flash On command are spacing
attributes which appear in the display just as if a standard space (20h)
had been received. Preamble Address Codes are non-spacing and will not
alter any attributes when used to position the cursor in the midst of a
row of characters.
(ii) The color attribute has the highest priority and can only be
changed by the Mid-Row Code of another color. Italics has the next
highest priority. If characters with both color and italics are desired,
the italics Mid-Row Code must follow the color assignment. Any color
Mid-Row Code will turn off italics. If the least significant bit of a
Preamble Address Code or of a color or italics Mid-Row Code is a 1
(high), underlining is turned on. If that bit is a 0 (low), underlining
is off.
(iii) The flash attribute is transmitted as a Miscellaneous Control
Code. The Flash On command will not alter the status of the color,
italics, or underline attributes. However, any color
[[Page 645]]
or italics Mid-Row Code will turn off flash.
(iv) Thus, for example, if a red, italicized, underlined, flashing
character is desired, the attributes must be received in the following
order: a red Mid-Row or Preamble Address Code, an italics Mid-Row Code
with underline bit, and the Flash On command. The character will then be
preceded by three spaces (two if red was assigned via a Preamble Address
Code).
(2) Display of attributes. The underline attribute will be displayed
by drawing a line beneath the character in the same color as the
character. The flash attribute will be displayed by causing the
character to blink from the display at least once per second. The italic
attribute must be capable of being displayed by either a special italic
font, or by the modification of the standard font by slanting. The user
may be given the option to select other methods of italic display as
well. The support of the color attributes is optional. If the color
attributes are supported, they will be displayed in the color they have
been assigned. If color attributes are not supported, the display may be
in color, but all color changes will be ignored.
(i) Control codes. There are three different types of control codes
used to identify the format, location, attributes, and display of
characters: Preamble Address Codes, Mid-Row Codes, and Miscellaneous
Control Codes.
(1) Each control code consists of a pair of bytes which are always
transmitted together in a single field of line 21 and which are normally
transmitted twice in succession to help insure correct reception of the
control instructions. The first of the control code bytes is a non-
printing character in the range 10h to 1Fh. The second byte is always a
printing character in the range 20h to 7Fh. Any such control code pair
received which has not been assigned a function is ignored. If the non-
printing character in the pair is in the range 00h to 0Fh, that
character alone will be ignored and the second character will be treated
normally.
(2) If the second byte of a control code pair does not contain odd
parity (see paragraph (j) of this section), then the pair is ignored.
The redundant transmission of the pair will be the instruction upon
which the receiver acts.
(3) If the first byte of the first transmission of a control code
pair fails the parity check, then that byte is inserted into the
currently active memory as a solid block character (7Fh) followed by
whatever the second byte is. Again, the redundant transmission of the
pair will be the controlling instruction.
(4) If the first transmission of a control code pair passes parity,
it is acted upon within one video frame. If the next frame contains a
perfect repeat of the same pair, the redundant code is ignored. If,
however, the next frame contains a different but also valid control code
pair, this pair, too, will be acted upon (and the receiver will expect a
repeat of this second pair in the next frame). If the first byte of the
expected redundant control code pair fails the parity check and the
second byte is identical to the second byte in the immediately preceding
pair, then the expected redundant code is ignored. If there are printing
characters in place of the redundant code, they will be processed
normally.
(5) There is provision for decoding a second data channel. The
second data channel is encoded with the same control codes and
procedures already described. The first byte of every control code pair
indicates the data channel (C1/C2) to which the command applies. Control
codes which do not match the data channel selected by the user, and all
subsequent data related to that control code, are ignored by the
receiver.
Mid-Row Codes
------------------------------------------------------------------------
Data Data
channel 1 channel 2 Attribute description
------------------------------------------------------------------------
11 20.... 19 20 White.
11 21.... 19 21 White Underline.
11 22.... 19 22 Green.
11 23.... 19 23 Green Underline.
11 24.... 19 24 Blue.
11 25.... 19 25 Blue Underline.
11 26.... 19 26 Cyan.
11 27.... 19 27 Cyan Underline.
11 28.... 19 28 Red.
11 29.... 19 29 Red Underline.
11 2A.... 19 2A Yellow.
11 2B.... 19 2B Yellow Underline.
11 2C.... 19 2C Magenta.
11 2D.... 19 2D Magenta Underline.
11 2E.... 19 2E Italics.
11 2F.... 19 2F Italics Underline.
[[Page 646]]
------------------------------------------------------------------------
Miscellaneous Control Codes
------------------------------------------------------------------------
Data Data
channel 1 channel 2 Mnemonic Command description
------------------------------------------------------------------------
14 20.... 1C 20 RCL................. Resume caption loading.
14 21.... 1C 21 BS.................. Backspace.
14 22.... 1C 22 AOF................. Reserved (formerly Alarm
Off).
14 23.... 1C 23 AON................. Reserved (formerly Alarm
On).
14 24.... 1C 24 DER................. Delete to End of Row.
14 25.... 1C 25 RU2................. Roll-Up Captions-2 Rows.
14 26.... 1C 26 RU3................. Roll-Up Captions-3 Rows.
14 27.... 1C 27 RU4................. Roll-Up Captions-4 Rows.
14 28.... 1C 28 FON................. Flash On.
14 29.... 1C 29 RDC................. Resume Direct Captioning.
14 2A.... 1C 2A TR.................. Text Restart.
14 2B.... 1C 2B RTD................. Resume Text Display.
14 2C.... 1C 2C EDM................. Erase Displayed Memory.
14 2D.... 1C 2D CR.................. Carriage Return.
14 2E.... 1C 2E ENM................. Erase Non-Displayed
Memory.
14 2F.... 1C 2F EOC................. End of Caption (Flip
Memories).
17 21.... 1F 21 TO1................. Tab Offset 1 Column.
17 22.... 1F 22 TO2................. Tab Offset 2 Columns.
17 23.... 1F 23 TO3................. Tab Offset 3 Columns.
[[Page 647]]
------------------------------------------------------------------------
Preamble Addre
ss Codes
-------------------------------------------------------------------------------
-------------------------------------------------------------------------
Row 1 Row 2 Row 3 Row 4 Row 5 Row
6 Row 7 Row 8 Row 9 Row 10 Row 11 Row 12 Row 13 Row 14 Row 15
-------------------------------------------------------------------------------
-------------------------------------------------------------------------
First byte of code pair:
Data Channel 1.............. 11 11 12 12 15 1
5 16 16 17 17 10 13 13 14 14
Data Channel 2.............. 19 19 1A 1A 1D 1
D 1E 1E 1F 1F 18 1B 1B 1C 1C
Second byte of code pair:
White....................... 40 60 40 60 40 6
0 40 60 40 60 40 40 60 40 60
White Underline............. 41 61 41 61 41 6
1 41 61 41 61 41 41 61 41 61
Green....................... 42 62 42 62 42 6
2 42 62 42 62 42 42 62 42 62
Green Underline............. 43 63 43 63 43 6
3 43 63 43 63 43 43 63 43 63
Blue........................ 44 64 44 64 44 6
4 44 64 44 64 44 44 64 44 64
Blue Underline.............. 45 65 45 65 45 6
5 45 65 45 65 45 45 65 45 65
Cyan........................ 46 66 46 66 46 6
6 46 66 46 66 46 46 66 46 66
Cyan Underline.............. 47 67 47 67 47 6
7 47 67 47 67 47 47 67 47 67
Red......................... 48 68 48 68 48 6
8 48 68 48 68 48 48 68 48 68
Red Underline............... 49 69 49 69 49 6
9 49 69 49 69 49 49 69 49 69
Yellow...................... 4A 6A 4A 6A 4A 6
A 4A 6A 4A 6A 4A 4A 6A 4A 6A
Yellow Underline............ 4B 6B 4B 6B 4B 6
B 4B 6B 4B 6B 4B 4B 68 4B 6B
Magenta..................... 4C 6C 4C 6C 4C 6
C 4C 6C 4C 6C 4C 4C 6C 4C 6C
Magenta Underline........... 4D 6D 4D 6D 4D 6
D 4D 6D 4D 6D 4D 4D 6D 4D 6D
White Italics............... 4E 6E 4E 6E 4E 6
E 4E 6E 4E 6E 4E 4E 6E 4E 6E
White Italics Underline..... 4F 6F 4F 6F 4F 6
F 4F 6F 4F 6F 4F 4F 6F 4F 6F
Indent 0.................... 50 70 50 70 50 7
0 50 70 50 70 50 50 70 50 70
Indent 0 Underline.......... 51 71 51 71 51 7
1 51 71 51 71 51 51 71 51 71
Indent 4.................... 52 72 52 72 52 7
2 52 72 52 72 52 52 72 52 72
Indent 4 Underline.......... 53 73 53 73 53 7
3 53 73 53 73 53 53 73 53 73
Indent 8.................... 54 74 54 74 54 7
4 54 74 54 74 54 54 74 54 74
Indent 8 Underline.......... 55 75 55 75 55 7
5 55 75 55 75 55 55 75 55 75
Indent 12................... 56 76 56 76 56 7
6 56 76 56 76 56 56 76 56 76
Indent 12 Underline......... 57 77 57 77 57 7
7 57 77 57 77 57 57 77 57 77
Indent 16................... 58 78 58 78 58 7
8 58 78 58 78 58 58 78 58 78
Indent 16 Underline......... 59 79 59 79 59 7
9 59 79 59 79 59 59 79 59 79
Indent 20................... 5A 7A 5A 7A 5A 7
A 5A 7A 5A 7A 5A 5A 7A 5A 7A
Indent 20 Underline......... 5B 7B 5B 7B 5B 7
B 5B 7B 5B 7B 5B 5B 7B 5B 7B
Indent 24................... 5C 7C 5C 7C 5C 7
C 5C 7C 5C 7C 5C 5C 7C 5C 7C
Indent 24 Underline......... 5D 7D 5D 7D 5D 7
D 5D 7D 5D 7D 5D 5D 7D 5D 7D
Indent 28................... 5E 7E 5E 7E 5E 7
E 5E 7E 5E 7E 5E 5E 7E 5E 7E
Indent 28 Underline......... 5F 7F 5F 7F 5F 7
F 5F 7F 5F 7F 5F 5F 7F 5F 7F
-------------------------------------------------------------------------------
-------------------------------------------------------------------------
Note: All indent codes (second byte equals 50h-5fh, 70th-7fh) assign white as t
he color attribute.
[[Page 648]]
(j) Data rejection. The receiver should provide an effective
procedure to verify data. A receiver will reject data if the data is
invalid, or if the data is directed to the data channel or field not
selected by the user. Invalid data is any data that fails to pass a
check for odd parity, or which, having passed the parity check, is
assigned no function.
(1) If a print character fails to pass a check for parity, a solid
block (7Fh) should be displayed in place of the failed character. In
addition, valid data can be corrupted in many ways and may not be
suitable for display. For example, repeated fields, skipped fields and
altered field sequences are all possible from consumer video equipment
and might present meaningless captions.
(2) The receiver will ignore data rejected due to being directed to
a deselected field or channel. However, this will not cause the display
to be disabled.
(k) Automatic display enable/disable. The receiver shall provide an
automatic enable/disable capability to prevent the display of invalid or
incomplete data, when the user selects the Caption Mode. The display
should automatically become enable after the receiver verifies the data
as described in paragraph (j) of this section. The display will be
automatically disabled when there is a sustained detection of invalid
data. The display will be re-enabled when the data verification process
has been satisfied once again.
(l) Compatibility with Cable Security Systems. Certain cable
television security techniques, such as signal encryption and copy
protection, can alter the television signal so that some methods of
finding line 21 will not work. In particular, counting of lines or
timing from the start of the vertical blanking interval may cause
problems. Caption decoding circuitry must function properly when
receiving signals from cable security systems that were designed and
marketed prior to April 5, 1991. Further information concerning such
systems is available from the National Cable Television Association,
Inc., Washington, DC, and from the Electronic Industries Association,
Washington, DC.
(m) Labelling and consumer information requirements. The box or
other package in which the individual television receiver is to be
marketed shall carry a statement in a prominent location, visible to the
buyer before purchase, which reads as follows:
This television receiver provides display of television closed
captioning in accordance with Sec. 15.119 of the FCC rules.
Receivers that do not support color attributes or text mode, as well as
receivers that display only upper-case characters pursuant to paragraph
(g) of this section, must include with the statement, and in the owner's
manual, language indicating that those features are not supported.
(n) Glossary of terms. The following terms are used to describe
caption decoder specifications:
(1) Base row: The bottom row of a roll-up display. The cursor always
remains on the base row. Rows of text roll upwards into the contiguous
rows immediately above the base row.
(2) Box: The area surrounding the active character display. In Text
Mode, the box is the entire screen area defined for display, whether or
not displayable characters appear. In Caption Mode, the box is
dynamically redefined by each caption and each element of displayable
characters within a caption. The box (or boxes, in the case of a
multiple-element caption) includes all the cells of the displayed
characters, the non-transparent spaces between them, and one cell at the
beginning and end of each row within a caption element in those decoders
that use a solid space to improve legibility.
(3) Caption window: The invisible rectangle which defines the top
and bottom limits of a roll-up caption. The window can be 2 to 4 rows
high. The lowest row of the window is called the base row.
(4) Cell: The discrete screen area in which each displayable
character or space may appear. A cell is one row high and one column
wide.
(5) Column: One of 32 vertical divisions of the screen, each of
equal width, extending approximately across the full width of the safe
caption area as defined in paragraph (n)(12) of this section. Two
additional columns, one
[[Page 649]]
at the left of the screen and one at the right, may be defined for the
appearance of a box in those decoders which use a solid space to improve
legibility, but no displayable characters may appear in those additional
columns. For reference, columns may be numbered 0 to 33, with columns 1
to 32 reserved for displayable characters.
(6) Displayable character: Any letter, number or symbol which is
defined for on-screen display, plus the 20h space.
(7) Display disable: To turn off the display of captions or text
(and accompanying background) at the receiver, rather than through codes
transmitted on line 21 which unconditionally erase the display. The
receiver may disable the display because the user selects an alternate
mode, e.g., TV Mode, or because no valid line 21 data is present.
(8) Display enable: To allow the display of captions or text when
they are transmitted on line 21 and received as valid data. For display
to be enabled, the user must have selected Caption Mode or Text Mode,
and valid data for the selected mode must be present on line 21.
(9) Element: In a pop-on or paint-on style caption, each contiguous
area of cells containing displayable characters and non-transparent
spaces between those characters. A single caption may have multiple
elements. An element is not necessarily a perfect rectangle, but may
include rows of differing widths.
(10) Erase Display: In Caption Mode, to clear the screen of all
characters (and accompanying background) in response to codes
transmitted on line 21. (The caption service provider can accomplish the
erasure either by sending an Erase Displayed Memory command or by
sending an Erase Non-Displayed Memory command followed by an End of
Caption command, effectively making a blank caption ``appear''.) Display
can also be erased by the receiver when the caption memory erasure
conditions are met, such as the user changing TV channels.
(11) Row: One of 15 horizontal divisions of the screen, extending
across the full height of the safe caption area as defined in paragraph
(n)(12) of this section.
(12) Safe caption area: The area of the television picture within
which captioning and text shall be displayed to ensure visibility of the
information on the majority of home television receivers. The safe
caption area is specified as shown in the following figure:
[[Page 650]]
[GRAPHIC] [TIFF OMITTED] TC03JN91.009
The dimensions of the above figure shall be as follows:
------------------------------------------------------------------------
Percent of
television
Label Dimensions picture
height
------------------------------------------------------------------------
A Television picture height....... 100.0
B Television picture width........ 133.33
C Height of safe caption area..... 80.0
D Width of safe caption area...... 106.67
E Vertical position of safe 10.0
caption area.
F Horizontal position of safe 13.33
caption area.
------------------------------------------------------------------------
(13) Special characters: Displayable characters (except for
``transparent space'') which require a two-byte sequence of one non-
printing and one printing character. The non-printing byte varies
depending on the data channel. Regular characters require unique one-
byte codes which are the same in either data channel.
(14) Text: When written with an upper-case ``T'', refers to the Text
Mode. When written with a lower-case ``t'', refers to any combination of
displayable characters.
(15) Transparent space: Transmitted as a special character, it is a
one-column-wide space behind which program video is always visible
(except when a transparent space immediately precedes or follows a
displayable character and solid box is needed to make that character
legible).
[ 56 FR 27201 , June 13, 1991, as amended at 57 FR 19094 , May 4, 1992; 58 FR 44893 , Aug. 25, 1993]
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