Skip to content
Glossary

What is EPUB media overlays?

Updated:

Media overlays synchronise recorded narration with the text of an EPUB 3, using SMIL files that pair audio clips with elements of the content documents. Reading apps highlight each phrase as it is read aloud.

Why it matters when you convert a PDF to EPUB

A PDF carries no narration, so converting one never produces media overlays; they are added later, for read-along books. They explain the MED messages in EPUBCheck, which check that clips and text references match.

Related terms

EPUBCheck messages about this

  • MED-009 The time specified in the clipBegin attribute must not be the same as clipEnd.
  • MED-003 Picture "img" elements must reference core media type resources, but found resource "…" of type "…".
  • MED-004 Image file header may be corrupted.

Convert a PDF to EPUB
Convert up to 5 pages free, no account needed.

FAQ

What is EPUB media overlays?

Media overlays synchronise recorded narration with the text of an EPUB 3, using SMIL files that pair audio clips with elements of the content documents. Reading apps highlight each phrase as it is read aloud.