FCC 15.119 Revised as of October 1, 2007
Goto Year:2006 |
2008
Sec. 15.119 Closed caption decoder requirements for analog 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 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
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 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 5×7 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 See note^1 Registered mark symbol
31 ° Degree sign
32 1/2 1/2
33 Inverse query
34 ^TM See note^1 Trademark symbol
35 Cents sign
36 Pounds Sterling sign
37 ♪ Music note
38 à A Lower-case a with grave accent
39 Transparent space
3A è E Lower-case e with grave accent
3B â A Lower-case a with circumflex
3C ê E Lower-case e with circumflex
3D î I Lower-case i with circumflex
3E ô O Lower-case o with circumflex
3F û U Lower-case u with circumflex
^1Note: The registered and trademark symbols are used to satisfy certain
legal requirements. There are various legal ways in which these symbols may
be drawn or displayed. For example, the trademark symbol may be drawn with
the “T” next to the “M” or over the “M”. It is preferred that the trademark
symbol be superscripted, i.e., XYZ^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
26 & Ampersand
27 ' Apostrophe
28 ( Open parentheses
29 ) Close parentheses
2A á 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 é E Lower-case e with acute accent
5D ] Close bracket
5E í I Lower-case i with acute accent
5F ó O Lower-case o with acute accent
60 ú 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 Sec. C Lower-case c with cedilla
7C ÷ Division sign
7D Ñ Upper-case N with tilde
7E ñ Ñ 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 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 channel 1 Data 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.
Miscellaneous Control Codes
Data channel 1 Data channel 2 Mne-
monic 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.
Preamble Address 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 15 16 16 17 17 10 13 13 14 14
Data Channel 2 19 19 1A 1A 1D 1D 1E 1E 1F 1F 18 1B 1B 1C 1C
Second byte of code pair:
White 40 60 40 60 40 60 40 60 40 60 40 40 60 40 60
White Underline 41 61 41 61 41 61 41 61 41 61 41 41 61 41 61
Green 42 62 42 62 42 62 42 62 42 62 42 42 62 42 62
Green Underline 43 63 43 63 43 63 43 63 43 63 43 43 63 43 63
Blue 44 64 44 64 44 64 44 64 44 64 44 44 64 44 64
Blue Underline 45 65 45 65 45 65 45 65 45 65 45 45 65 45 65
Cyan 46 66 46 66 46 66 46 66 46 66 46 46 66 46 66
Cyan Underline 47 67 47 67 47 67 47 67 47 67 47 47 67 47 67
Red 48 68 48 68 48 68 48 68 48 68 48 48 68 48 68
Red Underline 49 69 49 69 49 69 49 69 49 69 49 49 69 49 69
Yellow 4A 6A 4A 6A 4A 6A 4A 6A 4A 6A 4A 4A 6A 4A 6A
Yellow Underline 4B 6B 4B 6B 4B 6B 4B 6B 4B 6B 4B 4B 68 4B 6B
Magenta 4C 6C 4C 6C 4C 6C 4C 6C 4C 6C 4C 4C 6C 4C 6C
Magenta Underline 4D 6D 4D 6D 4D 6D 4D 6D 4D 6D 4D 4D 6D 4D 6D
White Italics 4E 6E 4E 6E 4E 6E 4E 6E 4E 6E 4E 4E 6E 4E 6E
White Italics Underline 4F 6F 4F 6F 4F 6F 4F 6F 4F 6F 4F 4F 6F 4F 6F
Indent 0 50 70 50 70 50 70 50 70 50 70 50 50 70 50 70
Indent 0 Underline 51 71 51 71 51 71 51 71 51 71 51 51 71 51 71
Indent 4 52 72 52 72 52 72 52 72 52 72 52 52 72 52 72
Indent 4 Underline 53 73 53 73 53 73 53 73 53 73 53 53 73 53 73
Indent 8 54 74 54 74 54 74 54 74 54 74 54 54 74 54 74
Indent 8 Underline 55 75 55 75 55 75 55 75 55 75 55 55 75 55 75
Indent 12 56 76 56 76 56 76 56 76 56 76 56 56 76 56 76
Indent 12 Underline 57 77 57 77 57 77 57 77 57 77 57 57 77 57 77
Indent 16 58 78 58 78 58 78 58 78 58 78 58 58 78 58 78
Indent 16 Underline 59 79 59 79 59 79 59 79 59 79 59 59 79 59 79
Indent 20 5A 7A 5A 7A 5A 7A 5A 7A 5A 7A 5A 5A 7A 5A 7A
Indent 20 Underline 5B 7B 5B 7B 5B 7B 5B 7B 5B 7B 5B 5B 7B 5B 7B
Indent 24 5C 7C 5C 7C 5C 7C 5C 7C 5C 7C 5C 5C 7C 5C 7C
Indent 24 Underline 5D 7D 5D 7D 5D 7D 5D 7D 5D 7D 5D 5D 7D 5D 7D
Indent 28 5E 7E 5E 7E 5E 7E 5E 7E 5E 7E 5E 5E 7E 5E 7E
Indent 28 Underline 5F 7F 5F 7F 5F 7F 5F 7F 5F 7F 5F 5F 7F 5F 7F
Note: All indent codes (second byte equals 50h–5fh, 70th–7fh) assign white
as the color attribute.
(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 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:
[ec03jn91.009.gif]
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The dimensions of the above figure shall be as follows:
Label Dimensions Percent of television 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 caption area 10.0
F Horizontal position of safe caption area 13.33
(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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