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EPUBCheck · Images, audio and media overlays

EPUBCheck MED_015: overlay out of reading order

Updated:

EPUBCheck MED_015 is a usage message: “Media overlay text references must be in reading order. Text target "…" is before the previous link target in … order.” The text references of a media overlay are not in reading order. A text target comes before the previous one in the document, so narration would jump backwards; EPUBCheck reports it as a usage note with -u.

The official message

Media overlay text references must be in reading order. Text target "%1$s" is before the previous link target in %2$s order.

Default severity
Usage. Informative only and hidden by default: it appears when EPUBCheck runs with -u (--usage). It does not make the EPUB invalid.
EPUBCheck version
5.4.0

EPUBCheck prints this ID with an underscore instead of a hyphen; this page uses the ID exactly as EPUBCheck reports it.

%1$s, %2$s… are filled in with the file, value or element EPUBCheck found.

Typical causes

  • par elements reordered by hand or by an editing tool.
  • Ids in the chapter that were renumbered after the overlay was made.

How to fix it

  1. Open the SMIL file and find the text target EPUBCheck names.
  2. Reorder the par elements so their text targets follow the order of the chapter, or fix the ids they point to.
  3. If the jump is intended (for example a sidebar read later), you can leave it.
  4. Rebuild the EPUB and run EPUBCheck again to confirm the message is gone.

When it's not this

The same check on the table of contents is NAV-011.

Terms used here

Other MED messages

  • MED_014 Media overlay audio file URLs must not have a fragment, but found '#…'.
  • MED_016 Media Overlays total duration should be the sum of the durations of all Media Overlays documents.
  • MED_013 Media Overlay Document referenced from the "media-overlay" attribute does not contain a reference to this Content Document.
  • MED_017 URL fragment should indicate an element ID, but found '#…'.
  • MED_012 The "media-overlay" attribute does not match the ID of the Media Overlay that refers to this document.
  • MED_018 URL fragment should be an SVG fragment identifier, but found '#…'.

Sources

Message text and severity from EPUBCheck 5.4.0 (W3C, BSD-3-Clause). Explanation by EpubCC.

FAQ

What does EPUBCheck MED_015 mean?

EPUBCheck MED_015 is a usage message: “Media overlay text references must be in reading order. Text target "…" is before the previous link target in … order.” The text references of a media overlay are not in reading order. A text target comes before the previous one in the document, so narration would jump backwards; EPUBCheck reports it as a usage note with -u.

Is MED_015 an error?

MED_015 is reported as usage by default. Informative only and hidden by default: it appears when EPUBCheck runs with -u (--usage). It does not make the EPUB invalid.