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Closed Caption Formats – Understand the Differences

Closed caption formats

With an array of different closed caption formats out there it can be a minefield knowing which one to use for your videos. In today’s blog we’ll take a look at the differences between different closed caption formats to see what makes each of them different from the rest and to see which one would best suit your requirements. 

Different broadcasters, video platforms and websites have different requirements and capabilities in terms of closed captioning. There are numerous formats available with different specifications. Some of the most popular captioning files are listed below.

EBU-STL Subtitles and Closed Captions

Often used for broadcast television, EBU-STL is a versatile format used for PAL broadcasts in Europe. In recent times, EBU-STL subtitles are slowly being superseded by EBU-TT which is a timed-text format.

  • STL captions can include forced narratives
  • Commonly used for placement changes
  • Different fonts and styling options are available
  • STL subtitles are frame based. Timings must be matched to the video frame rate and must be edited if exported to different frames per second, e.g. 25fps, 29.97fps (NonDrop), 50fps…
  • EBU-STL requires compatible software to open and edit.

SCC Subtitles and Closed Captions

This subtitle format is widely used by Premiere and FinalCut for uploading, editing, encoding and exporting DVD closed captions. SCC is also compatible with players such as YouTube and Vimeo.

  • SCC is a popular format for Line 21 broadcast closed captions.
  • Frame based, with a specified rate of 29.97fps (Drop / NonDrop).
  • SCC subtitles have a character limit of 37 characters per line.
  • Subtitles in the SCC format require compatible software to open. Times are displayed SMPTE and data is coded into two-byte hexidecimal words.

TTML (similar to DFXP) Closed Captions 

Commonly used for online video due to constraints on CEA-608 (line 21) features. The below features are available with DFXP and TTML subtitles.

  • DFXP and TTML closed captions are commonly used by video content providers such as Amazon and YouTube.
  • Time based subtitle format which works with videos of differing frame rates.
  • Flexible character and line restrictions.
  • Openable and editable using basic text readers, though video editing or subtitling software is recommended.

SMPTE-TT Closed Captioning 

These closed captions comprise an XML format similar to DFXP and TTML. However, SMPTE-TT subtitles are compliant with FCC broadcaster regulations and are compatible with CEA-608 (line 21) and CEA-708 (digital) caption capabilities.

  • Basic and advanced subtitle display options.
  • Recommended for foreign closed captioning and translations.
  • Forced narrative markers enabled for multilingual videos and informative text.
  • Standard 37 character per line limits.
  • Flexible frame based SMPTE subtitle format.

So there you go, we hope you have enjoyed reading this article about closed caption formats and found it informative. If you would like more information on the different closed captioning formats or would like to inquire about another service, contact us today for a free evaluation. 

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