Timed Text Requirements

Type	Descriptions
Closed Captions	Transcription of all spoken audio, key sounds, and visual elements for the hearing impaired (US broadcast)
Subtitles for Deaf & Hard of Hearing (SDH)	Original language or translation including key sounds and visual elements
Production / Full Subtitles	Translation of all spoken audio and on-screen text for international viewers
Forced Narratives	Translation of on-screen text and foreign dialogue not covered by the audio track
Full minus Forced Narratives	Translation of all spoken audio and on-screen text, omitting Forced Narratives

Reading speed: ≤ 18 characters per second (unless otherwise noted)
Text must be in sentence or mixed case. ALL CAPS is not allowed.
Italics may be used for songs, off-screen speech, phone/TV voices, etc.
Subtitle events should be raised to avoid obscuring on-screen text, graphics, or faces
No spaces can be used for alignment or padding
No subtitle zero
No events within 2 frames of scene changes or adjacent events
Event duration: ≥ 20 frames, ≤ 6 seconds
No spaces before or after subtitle text

Closed Captions must be C608 compliant, delivered as Scenarist Closed Caption (.scc).
Embedded start timecode must match the start timecode of the program, excluding any head build.
Closed Captions must use “pop-on” style. “roll-up” or “paint-on” style will be rejected.
Closed Captions must not exceed 32 characters per row, inclusive of spaces; maximum 2 rows of text.
Closed Captions must deliver as a 29.97 frame rate with the appropriate drop frame type:
- 29.97 NDF must be used for 23.976 video in hh:mm:ss:ff format
- 29.97 DF must be used for both 29.97NDF & 29.97DF video in hh:mm:ss;ff format
Scenarist Closed Captions are not accepted for 25fps content, please supply as EBU STL format

IMSC1.1 must be formatted as an XML compliant with W3C specification.
IMSC1.1 must be encoded as UTF-8
IMSC1.1 must be a text-only profile, an image-only profile is not supported
Text language must be defined in xml:lang in BCP47 format
IMSC1.1 should include ttp:framerate
IMSC1.1 must be authored with timeBase “media”
IMSC1.1 must be authored with tts:origin=”10% 10%” and tts:fontSize=”100%”
IMSC1.1 must not exceed 37 characters per row inclusive of spaces; maximum 2 rows of text
IMSC1.1 events must be authored as media time (hh:mm:ss.nnn) must have a start time 00:00:00.000 aligned to video file start time

For Japanese language only:

Vertical or Horizontal text positioning is permitted
Overlapping time cues are permitted, but text positioning must not overlap on screen
For italics, the use of tts:sheer set to 16.67% is recommended (~15°)
MS Gothic font (or very similar) is the recommended to meet regional expectations and avoid thin and widely spaced characters
Support of Rubies and Boutens is permitted to describe unfamiliar words, or convey pronunciation or cultural context
Support of kumi-moji / tate-chu-yoko horizontal characters is permitted for numbering or nonJapanese characters within vertical text

STL must be formatted as per EBU Open Tech. 3264 (.stl file extension)
STL must not exceed 37 characters per row, inclusive of spaces; maximum of 2 rows of text (except when intended as closed captions for US linear use, then it must not exceed 32 characters to meet the 608 spec)
GSI MNR (Maximum Number of displayable Rows) must be set to 23
STL events must match the video frame rate with the header framerate (Disc Format Code) conforming to:
- The header must be set to 30 when the video frame rate is 23.98fps or 29.97fps
  - The Subtitle cue timecodes in an STL authored for 23.98 video frame rate
    should us 29.97 non drop-frame and when the video frame rate is 29.97, then 29.97 drop frame is used.
- The header must be set to 25 for 25fps video and 25 fps non drop-frame timecode use for cue points.

Lambda CAP must be formatted as open subtitles (.cap file extension)
Lambda CAP supports the use of vertical glyphs, rubies, boutons, etc.
Reading speed must not exceed 4 characters per second
Lambda CAP must not exceed 2 rows of text for both vertical and horizontal
Underscores must not be used to position text
Vertical Text
- Limit: 11 full-width characters per line
- Full-width character, space, or punctuation = 1 character; half-width = 0.5 character
Horizontal Text
- Limit: 16 full-width characters per line
- Full-width character, space, or punctuation = 1 character; half-width = 0.5 character