C0 Table

NUL, BS, FF, and CR are interpreted as they are in ASCII control codes. HCR moves the pen location to the beginning of the current line and deletes its contents. FF clears the screen and moves the pen location to (0,0). ETX is the NULL command mentioned earlier, which is used to flush text to the current window when no other command is pending. EXT1 is used to escape to the 'C2', 'C3', 'G2', and 'G3' tables for the following byte. Finally, P16 can be used to escape the next two bytes for Chinese and other large character maps.

All characters in the range 0x10-0x17, which currently includes EXT1, are followed by one byte which needs to be interpreted differently. And, all characters in the range 0x18-x1f, which currently includes P16, are followed by two bytes that need to be interpreted differently. If a decoder encounters one of these and does not know what to do, it should still skip the next byte or two, as appropriate, before continuing.

C1 Table

The C1 Table contains all the currently defined caption commands. These will be described in detail in the next section.

C2 Table

The C2 Table contains no commands as of CTA-708 revision A. However, if a command is seen in these code sets a decoder must skip an appropriate number of the following bytes.

C3 Table

The C3 Table contains no commands as of CTA-708 revision A. However, if a command is seen in these code sets, a decoder must skip an appropriate number of the following bytes.

G0 Table

The G0 Table consists of ASCII characters for the most part. SP here is shorthand for Space. MN is a musical note, which replaces the Delete command code in ASCII, and can be any of "♩", "♪", "♫" or "♬", depending on the receiver manufacturer.

G1 Table

The G1 Table is basically the ISO 8859-1 Latin-1 character set. Note character 0xa0 is the non-breaking space, which is to be used to prevent word wrap from separating two words onto separate lines.

G2 Table

TSP and NBTSP are the Transparent Space, and Non-Breaking Transparent Space, respectively. The G2 Table contains miscellaneous characters that may not be displayed in all browsers. BLK indicates a solid block which fills the entire character block with a solid foreground color.

G3 Table

The G3 Table contains only a single character, the [CC] Icon, with square corners. This character is at 0xa0.

EndOfText (0x03)

The EndOfText command is a Null Command which can be used to flush any buffered text to the current window. All commands force a flush of any buffered text to the current window, so this command is only needed when no other command is pending.

SetCurrentWindow0-7 (0x80-0x87)

SetCurrentWindow tells the caption decoder which window the following commands describe: SetWindowAttributes, SetPenAttributes, SetPenColor, SetPenLocation. If the window specified has not already been created with a DefineWindow command then SetCurrentWindow and the window property commands can be safely ignored.

ClearWindows (0x88 + 1 byte)

ClearWindows clears all the windows specified in the 8 bit window bitmap.

DisplayWindows (0x89 + 1 byte)

DisplayWindows displays all the windows specified in the 8 bit window bitmap.

HideWindows (0x8A + 1 byte)

HideWindows hides all the windows specified in the 8 bit window bitmap.

ToggleWindows (0x8B + 1 byte)

ToggleWindows hides all displayed windows, and displays all hidden windows specified in the 8 bit window bitmap.

DeleteWindows (0x8C + 1 byte)

DeleteWindows deletes all the windows specified in the 8 bit window bitmap. If the current window, as specified by the last SetCurrentWindow command, is deleted then the current window becomes undefined and the window attribute commands should have no effect until after the next SetCurrentWindow or DefineWindow command.

Delay (0x8D + 1 byte)

Delay suspends all processing of the current service, except for DelayCancel and Reset scanning. The period of suspension is set to by the one byte parameter. The parameter specifies the delay in tenths of a second, so the minimum delay is 0.1 seconds, and the maximum delay is 25.5 seconds. A zero second delay can safely be ignored in a decoder, but should not be emitted from an encoder. A delay should be cancelled if the caption decoder's input buffer becomes full, a DelayCancel or Reset is received, or the specified delay time elapses.

DelayCancel (0x8E)

DelayCancel terminates any active delay and resumes normal command processing. DelayCancel should be scanned for during a Delay.

Reset (0x8F)

Reset deletes all windows, cancels any active delay, and clears the buffer before the Reset command. Reset should be scanned for during a Delay.

SetPenAttributes (0x90 + 2 bytes)

The SetPenAttributes command specifies how certain attributes of subsequent characters are to be rendered in the current window, until the next SetPenAttributes command. This command has the following parameters:

 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |TXT_TAG|OFS|PSZ| |I|U|EDTYP|FNTAG|
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 15             8   7             0
 OFS = offset ; PSZ = pen size
 I = italic toggle ; U = underline toggle
 EDTYP = edge type ; FNTAG = font tag

• pen size, 2 bits, { SMALL=0, STANDARD=1, LARGE=2, ILLEGAL_VAL=3 }
• offset, 2 bits, { SUBSCRIPT=0, NORMAL=1, SUPERSCRIPT=2, ILLEGAL_VAL=3 }
• text tag, 4 bits, { dialog=0, source_or_speaker_id=1, electronically_reproduced_voice=2, dialog_in_other_language=3, voiceover=4, audible_translation=5, subtitle_translation=6, voice_quality_description=7, song_lyrics=8, sound_effect_description=9, musical_score_description=10, oath=11, undefined_0=12,undefined_1=13,undefined_2=14, invisible=15 }
• font tag, 3 bits, { default=0, monospaced_serif=1, proportional_serif=2, monospaced_sanserif=3, proportional_sanserif=4, casual=5, cursive=6, smallcaps=7 }
• edge type, 3 bits, { NONE=0, RAISED=1, DEPRESSED=2, UNIFORM=3, LEFT_DROP_SHADOW=4, RIGHT_DROP_SHADOW=5, ILLEGAL_VAL0=6, ILLEGAL_VAL1=7 }
• underline, 1 bit, { NO=0, YES=1 }
• italic, 1 bit, { NO=0, YES=1 }

SetPenColor (0x91 + 3 bytes)

SetPenColor sets the foreground, background, and edge color for the subsequent characters. Color is specified with 6 bits, 2 for each of blue, green and red. The lowest order bits are for blue, the next two for green and the highest order bits represent red. Opacity is represented by two bits, they represent SOLID=0, FLASH=1, TRANSLUCENT=2, and TRANSPARENT=3. The edge color is the color of the outlined edges of the text, but the outline shares its opacity with the foreground, so the highest order bits of the third parameter byte should both be cleared. The parameters are as follows:

 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |FOP|F_R|F_G|F_B| |BOP|B_R|B_G|B_B| |0|0|E_R|E_G|E_B|
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 23             16 15             8   7             0
 FOP = foreground opacity ; BOP = background opacity
 F_? = foreground color component ; B_? = background color component
 E_? = edge color component

• foreground color, 6 bits
• foreground opacity, 2 bits
• background color, 6 bits
• background opacity, 2 bits
• edge color, 6 bits

SetPenLocation (0x92 + 2 bytes)

SetPenLocation sets the location of for the next bit of appended text in the current window. It has two parameters, row and column. If a window is not locked (see Define Window) and the SMALL font is in effect the location can be outside the otherwise valid addresses.

 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |0|0|0|0|  ROW  | |0|0|  COLUMN   |
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 15             8   7             0

• row, 4 bits, normally 0-14
• null padding, 4 bits
• column, 6 bits, normally 0-31 for 4:3 formats, and 0-41 for 16:9 formats
• null padding, 2 bits

SetWindowAttributes (0x97 + 4 bytes)

SetWindowAttributes Sets the window attributes of the current window. Fill Color is specified with 6 bits, 2 for each of blue, green and red. The lowest order bits are for blue, the next two for green and the highest order bits represent red. Fill Opacity is represented by two bits, they represent SOLID=0, FLASH=1, TRANSLUCENT=2, and TRANSPARENT=3. The window's Border Color is specified the same way. However, the Border Type is split into two fields. They should be combined, with border type 01 representing the low order bits, and border type 2 the high order bit. Once combined the Border Type has 6 valid values: NONE=0, RAISED=1, DEPRESSED=2, UNIFORM=3, SHADOW_LEFT=4, and SHADOW_RIGHT=5.

 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |FOP|F_R|F_G|F_B| |BTP|B_R|B_G|B_B| |W|B|PRD|SCD|JST| |EFT_SPD|EFD|DEF|
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 31             24 23             16 15             8   7             0
 FOP = fill opacity ; BTP = border type lower bits; B = border type upper bit
 F_? = fill color component ; B_? = border color component
 W = word wrap toggle ; PRD = print direction ; SCD = scroll direction
 JST = justification ; EFT_SPD = effect speed ; EFD = effect direction ; DEF = display effect

• fill color, 6 bits. Window interior color.
• fill opacity, 2 bits. { SOLID=0, FLASH=1, TRANSLUCENT=2, and TRANSPARENT=3 }
• border color, 6 bits. Window border color.
• border type 01, 2 bits. See discussion above.
• justify, 2 bits. For Left-to-Right and Right-to-Left print directions the values are: {LEFT=0, RIGHT=1, CENTER=2, FULL=3}, for Top-to-Bottom and Bottom-to-Top print directions the values are: TOP=0, BOTTOM=1, CENTER=2, FULL=3

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.

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.

• scroll direction, 2 bits. This specifies which direction text will scroll when the end of a caption "line" is reached. It has one of four values: LEFT_TO_RIGHT=0, RIGHT_TO_LEFT=1, TOP_TO_BOTTOM=2, and BOTTOM_TO_TOP=3.
• print direction, 2 bits. This specifies how order text is added to a window. It has one of four values: LEFT_TO_RIGHT=0, RIGHT_TO_LEFT=1, TOP_TO_BOTTOM=2, and BOTTOM_TO_TOP=3.
• word wrap, 1 bit. If set word wrapping is enabled, otherwise word wrap should not be employed.
• border type 2, 1 bits. See discussion above.
• display effect, 2 bits. This specifies an effect to be used to display or hide a window. It has one of three valid values: SNAP=0, FADE=1, and WIPE=2. SNAP means the window should assume full opacity immediately. FADE means the window should fade in or out at effect speed. Finally, WIPE means the window should fly onto or off the screen from the border of the screen border specified in effect direction at the rate specified in effect speed
• effect direction, 2 bits. This specifies where a wipe effect comes from on window display. It has one of four values: LEFT_TO_RIGHT=0, RIGHT_TO_LEFT=1, TOP_TO_BOTTOM=2, and BOTTOM_TO_TOP=3. When the window is wiped off the screen it should be wiped off in the opposite direction from how it was wiped onto the screen.
• effect speed, 4 bits. This specifies in half-seconds how long a caption display or hide effect, such as FADE, and WIPE, should take. The maximum time is 7.5 seconds, and the minimum non-zero value is 0.5 seconds.

Colors, text painting, effects, and border types can be customized with the SetWindowAttributes and SetPenAttributes commands. However, the caption provider may wish to use predefined standard window styles. A set of predefined styles will be hard stored in receivers. This set will anticipate the most widely used types of caption windows in order to conserve caption channel bandwidth by eliminating the need to transmit superfluous SetWindowAttributes and SetPenAttributes commands.

Predefined window and pen styles can be specified by the window style and pen style ID parameters in the DefineWindow command.

DefineWindow07 (0x98-0x9F, + 6 bytes)

DefineWindow0-7 creates one of the eight windows used by a caption decoder. This command should be sent periodically by a caption encoder even for pre-existing windows so that a newly tuned in caption decoder can begin displaying captions. When issued on a pre-existing window the pen style and window style can be left null, this tells the decoder not to change the current styles if they exist, and initialize both to style 1 if the window does not exist in its context.

 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |0|0|V|R|C|PRIOR| |P| VERT_ANCHOR | |  HOR_ANCHOR   |
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 47             40 39             32 31             24
 V = visible ; R = row lock toggle ; C = column lock toggle
 PRIOR = priority ; P = relative toggle
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |ANC_ID |ROW_CNT| |0|0| COL_COUNT | |0|0|WNSTY|PNSTY|
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 23             16 15             8   7             0
 WNSTY = window style ; PNSTY = pen style

The parameters are as follows:

• priority, 3 bits, 0-7. A decoder is only required to display up to four windows. If more than four displayed windows are requested, the decoder should display the four highest priority windows.
• column lock, 1 bit. If set, column lock fixes the absolute number of columns to be displayed. If not set, a caption decoder may display more columns of text when the font size permits it, and a SetPenLocation command may go to a location outside the defined window size.
• row lock, 1 bit. If set, row lock fixes the absolute number of rows to be displayed. If not set, a caption decoder may display more rows of text when the font size permits it, and a SetPenLocation command may go to a location outside the defined window size.
• visible, 1 bit. If set, this flag causes the window to be displayed upon creation, if not set, the window is initially hidden.
• null, 2 bits. Null padding.
• anchor vertical, 7 bits. Vertical position of the window's anchor point. The range is normally 0-74. When the relative positioning bit is set however the range is 0-99.
• relative positioning, 1 bit. If set, the anchor horizontal and anchor vertical represent relative coordinates, percentages, instead of regular coordinates.
• anchor horizontal, 8 bits. Horizontal position of the window's anchor point. The range is normally 0-209 when the stream's aspect ratio is 16:9, and 0-159 when the stream's aspect ratio is 4:3. When the relative positioning bit is set however the range is 0-99.
• row count, 4 bits. This is the number of rows of text, assuming the STANDARD font size, the window will hold. The range is 0-15. NOTE: In practice a decoder must add one to the number to get the intended effect. i.e. 0 -> 1, 1 -> 2, etc.
• anchor ID, 4 bits. Valid Values: { UPPER_LEFT=0, UPPER_CENTER=1, UPPER_RIGHT=2, MIDDLE_LEFT=3, MIDDLE_CENTER=4, MIDDLE_RIGHT=5, LOWER_LEFT=6, LOWER_CENTER=7, LOWER_RIGHT=8 }
• column count, 6 bits. This is the number of columns of text, assuming the STANDARD font size, the window will hold. The range is 0-31 for 4:3 streams, and 0-41 for 16:9 streams. NOTE: In practice a decoder must add one to the number to get the intended effect. i.e. 0 -> 1, 1 -> 2, etc.
• null, 2 bits. Null padding.
• pen style, 3 bits. If the value is zero and this is a new window, pen style one should be used for future characters. If the value is zero and this is an existing window, the previous pen style should continue to be used. For non-zero values the pen style should be set as if SetPenStyle were called with the parameters in the pen style table, below.
• window style, 3 bits. If the value is zero and this is a new window, window style one should be used for future characters. If the value is zero and this is an existing window, the previous window style should continue to be used. For non-zero values the window style should be set as if SetWindowStyle were called with the parameters in the window style table below.
• null, 2 bits. Null padding.