You are here: joeclark.org → Accessibility → Captioning → Best practices in online captioning

Comparison with other formats

Each captioning medium has its own constraints and behaviours. Here we compare older captioning media against online captioning. In all cases, we’re talking about online captioning as carried out through player features rather than through burned-in open captioning. Indeed, no form of open captioning is considered.

Medium Common to both Not available online Available only online
Line 21
  • Left and centre justification
  • Italics
  • Colour
  • Multiple streams
  • Paint-on and blink styles
  • Right justification (not on all online platforms)
  • Multiple onscreen blocks (without space characters for padding)
  • Variable alignment, as at tab stops
  • Full-screen addressing
  • Type attributes like bold
  • Non-Latin characters; wider range of Latin characters
  • Multiple fonts
  • Offscreen display
DVD subpictures and DVB
  • Multiple fonts
  • Type attributes like bold, italic
  • Colour (rare in DVD)
  • Non-Latin characters; full Latin character set
  • Multiple streams
  • Full-screen addressing
  • Variable alignment
  • Illustrations, pictograms, and graphics
  • Offscreen display
  • Scrolling (theoretically possible in DVD)
Rear Window®
  • Left and centre justification (right justification is possible but not used)
  • Offscreen display
 [None significant]
  • Multiple streams
  • Accented Latin characters; non-Latin characters
  • Selectable fonts
  • Type attributes
  • Colour
Teletext
  • Left and centre justification
  • Multiple streams
  • Right justification (not on all online platforms)
  • Multiple onscreen blocks (without space characters for padding)
  • Variable alignment, as at tab stops
  • Full-screen addressing
  • Type attributes like bold, italic
  • Some non-Latin characters; wider range of Latin characters
  • Multiple fonts per caption (on some platforms)
  • Offscreen display