Goto Section: 15.121 | 15.123 | Table of Contents
Revised as of October 1, 2009
Goto Year:2008 |
§ 15.122 Closed caption decoder requirements for digital television
receivers and converter boxes.
(a)(1) Effective July 1, 2002, all digital television receivers with
picture screens in the 4:3 aspect ratio with picture screens measuring
13 inches or larger diagonally, all digital television receivers with
picture screens in the 16:9 aspect ratio measuring 7.8 inches or larger
vertically and all separately sold DTV tuners shipped in interstate
commerce or manufactured in the United States shall comply with the
provisions of this section.
Note to paragraph(a)(1): This paragraph places no restrictions on the
shipping or sale of digital television receivers that were manufactured
before July 1, 2002.
(2) Effective July 1, 2002, DTV converter boxes that allow digitally
transmitted television signals to be displayed on analog receivers
shall pass available analog caption information to the attached
receiver in a form recognizable by that receiver's built-in caption
Note to paragraph(a)(2): This paragraph places no restrictions on the
shipping or sale of DTV converter boxes that were manufactured before
July 1, 2002.
(b) Digital television receivers and tuners must be capable of decoding
closed captioning information that is delivered pursuant to EIA–708–B:
“Digital Television (DTV) Closed Captioning” (incorporated by
reference, see § 15.38).
(c) Services. (1) Decoders must be capable of decoding and processing
data for the six standard services, Caption Service #1 through Caption
(2) Decoders that rely on Program and System Information Protocol data
to implement closed captioning functions must be capable of decoding
and processing the Caption Service Directory data. Such decoders must
be capable of decoding all Caption Channel Block Headers consisting of
Standard Service Headers, Extended Service Block Headers, and Null
Block headers. However, decoding of the data is required only for
Standard Service Blocks (Service IDs <-6), and then only if the
characters for the corresponding language are supported. The decoders
must be able to display the directory for services 1 through 6.
(d) Code space organization. (1) Decoders must support Code Space C0,
G0, C1, and G1 in their entirety.
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(2) The following characters within code space G2 must be supported:
(i) Transparent space ([TSP]).
(ii) Non-breaking transparent space ([NBTSP]).
(iii) Solid block ( ).
(iv) Trademark symbol (^TM ).
(v) Latin-1 characters Š, Œ, š, œ, Ÿ.
(3) The substitutions in Table 2 are to be made if a decoder does not
support the remaining G2 characters.
Table 2—G2 Character Substitution Table
G2 Character Substitute with
Open single quote (‘), G2 char code 0×31 G0 single quote (‘), char code
Close single quote (’), G2 char code 0×32 G0 single quote ('), char
Open double quote (“), G2 char code 0×33 G0 double quote (“), char code
Close double quote (”), G2 char code 0×34 G0 double quote (”), char
Bold bullet (•), G2 char code 0×35 G1 bullet (•), char code 0×B7
Elipsis (. . .), G2 char code 0×25 G0 underscore (_), char code 0×5F
One-eighth ( 1/8), G2 char code 0×76 G0 percent sign (%), char code
Three-eighths ( 3/8), G2 char code 0×77 G0 percent sign (%), char code
Five-eighths ( 5/8), G2 char code 0×78 G0 percent sign (%), char code
Seven-eighths ( 7/8), G2 char code 0×79 G0 percent sign (%), char code
Vertical border (|), G2 char code 0×7A G0 stroke (|), char code 0×7C
Upper-right border (⌉), G2 char code 0×7B G0 dash (-), char code 0×2D
Lower-left border (⌊), G2 char code 0×7C G0 dash (-), char code 0×2D
Horizontal border (―), G2 char code 0×7D G0 dash (-), char code 0×2D
Lower-right border (⌋), G2 char code 0×7E G0 dash (-), char code 0×2D
Upper-left border (⌈), G2 char code 0×7F G0 dash (-), char code 0×2D
(4) Support for code spaces C2, C3, and G3 is optional. All unsupported
graphic symbols in the G3 code space are to be substituted with the G0
underscore character (_), char code 0×5F.
(e) Screen coordinates. Table 3 specifies the screen coordinate
resolutions and limits for anchor point positioning in 4:3 and 16:9
display formats, and the number of characters per row.
Table 3—Screen Coordinate Resolutions and Limits
Screen aspect ratio Maximum anchor position resolution Minimum anchor
position resolution Maximum displayed rows Maximum characters per row
4:3 75v×160h 15v×32h 4 32
16:9 75v×210h 15v×42h 4 42
Other 75v×(5×H) 15v×H* 4 ^1
^1H = 32 × (the width of the screen in relation to a 4:3 display). For
example, the 16:9 format is 1/3 wider than a 4:3 display; thus, H = 32
* 4/3 = 42.667, or 42.
(1) This means that the minimum grid resolution for a 4:3 aspect ratio
instrument is 15 vertical positions × 32 horizontal positions. This
minimum grid resolution for 16:9 ratio instrument is 15 vertical
positions × 42 horizontal positions. These minimum grid sizes are to
cover the entire safe-title area of the corresponding screen.
(2) The minimum coordinates equate to a1/5reduction in the maximum
horizontal and vertical grid resolution coordinates. Caption providers
are to use the maximum coordinate system values when specifying anchor
point positions. Decoders using the minimum resolution are to divide
the provided horizontal and vertical screen coordinates by 5 to derive
the equivalent minimum coordinates.
(3) Any caption targeted for both 4:3 and 16:9 instruments is limited
to 32 contiguous characters per row. If a caption is received by a 4:3
instrument that is targeted for a 16:9 display only, or requires a
window width greater than 32 characters, then the caption may be
completely disregarded by the decoder. 16:9 instruments should be able
to process and display captions intended for 4:3 displays, providing
all other minimum recommendations are met.
(4) If the resulting size of any window is larger than the safe title
area for the corresponding display's aspect ratio, then this window
will be completely disregarded.
(f) Caption windows. (1) Decoders need to display no more than 4 rows
of captions on the screen at any given time, regardless of the number
of windows displayed. This implies that no more than 4 windows can be
displayed at any given time (with each having only one caption row).
However, decoders should maintain storage to support a minimum total of
8 rows of captions. This storage is needed for the worst-case support
of a displayed window with 4 rows of captioning and a non-displayed
window which is buffering the incoming rows for the next 4-row caption.
As implied above, the maximum number of windows that may be displayed
at any one time by a minimum decoder implementation is 4. If more than
4 windows are defined in the caption stream, the decoder may disregard
the youngest and lowest priority window definition(s). Caption
providers must be aware of this limitation, and either restrict the
total number of windows used or accept that some windows will not be
(2) Decoders do not need to support overlapped windows. If a window
overlaps another window, the overlapped window need not be displayed by
(3) At a minimum, decoders will assume that all windows have rows and
columns “locked”. This implies that if a decoder implements the SMALL
pen-size, then word-“un”wrapping, when shrinking captions, need not be
implemented. Also, if a decoder implements the LARGE pen size, then
word wrapping (when enlarging captions) need not be implemented.
(4) Whenever possible, the receiver should render embedded carriage
returns as line breaks, since these carriage returns indicate an
important aspect of the caption's formatting as determined by the
service provider. However, it may sometimes be necessary for the
receiver to ignore embedded line breaks. For example, if a caption is
to appear in a larger font, and if its window's rows and/or columns are
unlocked, the rows of text may need to become longer or shorter to fit
within the allocated space. Such automatic reformatting of a caption is
known as “word wrap.” If decoders support word-wrapping, it must be
implemented as follows:
(i) The receiver should follow standard typographic practice when
implementing word wrap. Potential breaking points (word-wrapping
points) are indicated by the space character (20h) and by the hyphen
(ii) If a row is to be broken at a space, the receiver should remove
the space from the caption display. If a row is to be broken after a
hyphen, the hyphen should be retained.
(iii) If an embedded return is to be removed, it should usually be
replaced with a space. However, if the character to the left of the
embedded return is a hyphen, the embedded return should be removed but
NOT replaced with a space.
(iv) This specification does not include optional hyphens, nor does it
provide for any form of automatic hyphenation. No non-breaking hyphen
is defined. The non-breaking space (A0h in the G1 code set) and the
non-breaking transparent space (21h in the G2 code set) should not be
considered as potential line breaks.
(v) If a single word exceeds the length of a row, the word should be
placed at the start of a new row, broken at the character following the
last character that fits on the row, and continued with further breaks
(g) Window text painting. (1) All decoders should implement “left”,
“right”, and “center” caption-text justification. Implementation of
“full” justification is optional. If “full” justification is not
implemented, fully justified captions should be treated as though they
are “left” justified.
(i) For “left” justification, decoders should display any portion of a
received row of text when it is received. For “center”, “right”, and
“full” justification, decoders may display any portion of a received
row of text when it is received, or may delay display of a received row
of text until reception of a row completion indicator. A row completion
indicator is defined as receipt of a CR, ETX or any other command,
except SetPenColor, SetPenAttributes, or SetPenLocation where the pen
relocation is within the same row.
(ii) Receipt of a character for a displayed row which already contains
text with “center”, “right” or “full” justification will cause the row
to be cleared prior to the display of the newly received character and
any subsequent characters. Receipt of a justification command which
changes the last received justification for a given window will cause
the window to be cleared.
(2) At a minimum, decoders must support LEFT_TO_RIGHT printing.
(3) At a minimum, decoders must support BOTTOM_TO_TOP scrolling. For
windows sharing the same horizontal scan lines on the display,
scrolling may be disabled.
(4) At a minimum, decoders must support the same recommended practices
for scroll rate as is provided for NTSC closed-captioning.
(5) At a minimum, decoders must support the same recommended practices
for smooth scrolling as is provided for NTSC closed-captioning.
(6) At a minimum, decoders must implement the “snap” window display
effect. If the window “fade” and “wipe” effects are not implemented,
then the decoder will “snap” all windows when they are to be displayed,
and the “effect speed” parameter is ignored.
(h) Window colors and borders. At a minimum, decoders must implement
borderless windows with solid, black backgrounds (i.e., border type =
NONE, fill color = (0,0,0), fill opacity = SOLID), and borderless
transparent windows (i.e., border type = NONE, fill opacity =
(i) Predefined window and pen styles. Predefined Window Style and Pen
Style ID's may be provided in the DefineWindow command. At a minimum,
decoders should implement Predefined Window Attribute Style 1 and
Predefined Pen Attribute Style 1, as shown in Table 4 and Table 5,
Table 4—Predefined Window Style ID's
Style ID # Justify Print direction Scroll
direction Word wrap Display
speed Fill color Fill opacity Border type Border color Usage
1 Left Left-to-right Bottom-to-top No Snap n/a n/a (0,0,0) Black Solid
None n/a NTSC Style PopUp Captions
2 Left Left-to-right Bottom-to-top No Snap n/a n/a n/a Transparent None
n/a PopUp Captions w/o Black Background
3 Cntr Left-to-right Bottom-to-top No Snap n/a n/a (0,0,0) Black Solid
None n/a NTSC Style Centered PopUp Captions
4 Left Left-to-right Bottom-to-top Yes Snap n/a n/a (0,0,0) Black Solid
None n/a NTSC Style RollUp Captions
5 Left Left-to-right Bottom-to-top Yes Snap n/a n/a n/a Transparent
None n/a RollUp Captions w/o Black Background
6 Cntr Left-to-right Bottom-to-top Yes Snap n/a n/a (0,0,0) Black Solid
None n/a NTSC Style Centered RollUp Captions
7 Left Top-to-bottom Right-to-left No Snap n/a n/a (0,0,0) Black Solid
None n/a Ticker Tape
Table 5—Predefined Pen Style ID's
Predefined style ID Pen size Font style Offset Italics Underline Edge
type Foregrnd color Foregrnd opacity Backgrnd color Backgrnd opacity
Edge color Usage
1 Stndr 0 Normal No No None (2,2,2) White Solid (0,0,0) Black Solid n/a
Default NTSC Style*
2 Stndr 1 Normal No No None (2,2,2) Solid (0,0,0) White Solid n/a NTSC
Style* Mono w/Serif
3 Stndr 2 Normal No No None (2,2,2) White Solid (0,0,0) Black Solid n/a
NTSC Style* Prop w/ Serif
4 Stndr 3 Normal No No None (2,2,2) White Solid (0,0,0) Black Solid n/a
NTSC Style* Mono w/o Serif
5 Stndr 4 Normal No No None (2,2,2) White Solid (0,0,0) Black Solid n/a
NTSC Style* Prop w/o Serif
6 Stndr 3 Normal No No Unifrm (2,2,2) White Solid n/a Transparent
(0,0,0) Black Mono w/o Serif, Bordered Text, No BG
7 Stndr 4 Normal No No Unifrm (2,2,2) White Solid n/a Transparent
(0,0,0) Black Prop. w/o Serif, Bordered Text, No BG
*“NTSC Style”—White Text on Black Background
(j) Pen size. (1) Decoders must support the standard, large, and small
pen sizes and must allow the caption provider to choose a pen size and
allow the viewer to choose an alternative size. The STANDARD pen size
should be implemented such that the height of the tallest character in
any implemented font is no taller than1/15of the height of the
safe-title area, and the width of the widest character is no wider
than1/32of the width of the safe-title area for 4:3 displays and1/42of
the safe-title area width for 16:9 displays.
(2) The LARGE pen size should be implemented such that the width of the
widest character in any implemented font is no wider than1/32of the
safe-title area for 16:9 displays. This recommendation allows for
captions to grow to a LARGE pen size without having to reformat the
caption since no caption will have more than 32 characters per row.
(k) Font styles. (1) Decoders must support the eight fonts listed
below. Caption providers may specify 1 of these 8 font styles to be
used to write caption text. The styles specified in the “font style”
parameter of the SetPenAttributes command are numbered from 0 through
7. The following is a list of the 8 required font styles. For
information purposes only, each font style references one or more
popular fonts which embody the characteristics of the style:
(i) 0—Default (undefined)
(ii) 1—Monospaced with serifs (similar to Courier)
(iii) 2—Proportionally spaced with serifs (similar to Times New Roman)
(iv) 3—Monospaced without serifs (similar to Helvetica Monospaced)
(v) 4—Proportionally spaced without serifs (similar to Arial and Swiss)
(vi) 5—Casual font type (similar to Dom and Impress)
(vii) 6—Cursive font type (similar to Coronet and Marigold)
(viii) 7—Small capitals (similar to Engravers Gothic)
(2) Font styles may be implemented in any typeface which the decoder
manufacturer deems to be a readable rendition of the font style, and
need not be in the exact typefaces given in the example above. Decoders
must include the ability for consumers to choose among the eight fonts.
The decoder must display the font chosen by the caption provider unless
the viewer chooses a different font.
(l) Character offsetting. Decoders need not implement the character
offsetting ( i.e., subscript and superscript) pen attributes.
(m) Pen styles. At a minimum, decoders must implement normal, italic,
and underline pen styles.
(n) Foreground color and opacity. (1) At a minimum, decoders must
implement transparent, translucent, solid and flashing character
foreground type attributes.
(2) At a minimum, decoders must implement the following character
foreground colors: white, black, red, green, blue, yellow, magenta and
(3) Caption providers may specify the color/opacity. Decoders must
include the ability for consumers to choose among the color/opacity
options. The decoder must display the color/opacity chosen by the
caption provider unless the viewer chooses otherwise.
(o) Background color and opacity. (1) Decoders must implement the
following background colors: white, black, red, green, blue, yellow,
magenta and cyan. It is recommended that this background is extended
beyond the character foreground to a degree that the foreground is
separated from the underlying video by a sufficient number of
background pixels to insure the foreground is separated from the
(2) Decoders must implement transparent, translucent, solid and
flashing background type attributes. Caption providers may specify the
color/opacity. Decoders must include the ability for consumers to
choose among the color/opacity options. The decoder must display the
color/opacity chosen by the caption provider unless the viewer chooses
(p) Character edges. Decoders must implement separate edge color and
type attribute control.
(q) Color representation. (1) At a minimum, decoders must support the 8
colors listed in Table 6.
Table 6—Minimum Color List Table
Color Red Green Blue
Black 0 0 0
White 2 2 2
Red 2 0 0
Green 0 2 0
Blue 0 0 2
Yellow 2 2 0
Magenta 2 0 2
Cyan 0 2 2
(2)(i) When a decoder supporting this Minimum Color List receives an
RGB value not in the list, it will map the received value to one of the
values in the list via the following algorithm:
(A) All one (1) values are to be changed to 0.
(B) All two (2) values are to remain unchanged.
(C) All three (3) values are to be changed to 2.
(ii) For example, the RGB value (1,2,3) will be mapped to (0,2,2),
(3,3,3) will be mapped to (2,2,2) and (1,1,1) will be mapped to
(3) Table 7 is an alternative minimum color list table supporting 22
Table 7—Alternative Minimum Color List Table
Color Red Green Blue
Black 0 0 0
Gray 1 1 1
White 2 2 2
Bright White 3 3 3
Dark Red 1 0 0
Red 2 0 0
Bright Red 3 0 0
Dark Green 0 1 0
Green 0 2 0
Bright Green 0 3 0
Dark Blue 0 0 1
Blue 0 0 2
Bright Blue 0 0 3
Dark Yellow 1 1 0
Yellow 2 2 0
Bright Yellow 3 3 0
Dark Magenta 1 0 1
Magenta 2 0 2
Bright Magenta 3 0 3
Dark Cyan 0 1 1
Cyan 0 2 2
Bright Cyan 0 3 3
(i) When a decoder supporting the Alternative Minimum Color List in
Table 7 receives an RGB value not in the list (i.e., an RGB value whose
non-zero elements are not the same value), it will map the received
value to one of the values in the list via the following algorithm:
(A) For RGB values with all elements non-zero and different—e.g.,
(1,2,3), (3,2,1), and (2,1,3), the 1 value will be changed to 0, the 2
value will remain unchanged, and the 3 value will be changed to 2.
(B) For RGB values with all elements non-zero and with two common
elements—e.g. (3,1,3), (2,1,2), and (2,2,3), if the common elements are
3 and the uncommon one is 1, then the 1 elements is changed to 0; e.g.
(3,1,3) → (3,0,3). If the common elements are 1 and the uncommon
element is 3, then the 1 elements are changed to 0, and the 3 element
is changed to 2; e.g. (1,3,1) → (0,2,0). In all other cases, the
uncommon element is changed to the common value; e.g., (2,2,3) →
(2,2,2), (1,2,1) → (1,1,1), and (3,2,3) → (3,3,3).
(ii) All decoders not supporting either one of the two color lists
described above, must support the full 64 possible RGB color value
(r) Character rendition considerations. In NTSC Closed Captioning,
decoders were required to insert leading and trailing spaces on each
caption row. There were two reasons for this requirement:
(1) To provide a buffer so that the first and last characters of a
caption row do not fall outside the safe title area, and
(2) To provide a black border on each side of a character so that the
“white” leading pixels of the first character on a row and the trailing
“white” pixels of the last character on a row do not bleed into the
(i) Since caption windows are required to reside in the safe title area
of the DTV screen, reason 1 (above) is not applicable to DTVCC
(ii) The attributes available in the SetPenAttributes command for
character rendition (e.g., character background and edge attributes)
provide unlimited flexibility to the caption provider when describing
caption text in an ideal decoder implementation. However, manufacturers
need not implement all pen attributes. Thus it is recommended that no
matter what the level of implementation, decoder manufacturers should
take into account the readability of all caption text against a variety
of all video backgrounds, and should implement some automatic character
delineation when the individual control of character foreground,
background and edge is not supported.
(s) Service synchronization. Service Input Buffers must be at least 128
bytes in size. Caption providers must keep this lower limit in mind
when following Delay commands with other commands and window text. In
other words, no more than 128 bytes of DTVCC commands and text should
be transmitted (encoded) before a pending Delay command's delay
(t) Settings. Decoders must include an option that permits a viewer to
choose a setting that will display captions as intended by the caption
provider (a default). Decoders must also include an option that allows
a viewer's chosen settings to remain until the viewer chooses to alter
these settings, including periods when the television is turned off.
[ 65 FR 58471 , Sept. 29, 2000, as amended at 69 FR 2849 , Jan. 21, 2004]
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