Overview: Subtitle formats

Subtitle formats define the timed content, graphics or service information available for presentation.

Some formats carry text and styling instructions; others carry ready-made images or caption-service data. That distinction changes the work a renderer performs. The format branches below establish the representation first, before storage, delivery and player support determine how it reaches the viewer.

• Subtitle formats explained
  A subtitle format defines how timing, text or image content, and presentation information are encoded separately from their storage or delivery.

• Text subtitle formats
  Text subtitle formats combine cue timing with character content and format-specific presentation rules.

• IMSC timed text
  IMSC defines constrained TTML profiles for interoperable internet-media subtitles and captions, with version-specific text and image capabilities.

• Bitmap subtitle formats
  Bitmap subtitles carry timed graphic elements that a renderer composites with the picture.

• Broadcast captions
  Broadcast captions use defined services and signaling to carry timed text and related presentation information.