Media clips need an Alt entry

PDF/UA check MEDIA_CLIP_ALT · Annotations · severity High · PDF/UA 8.9.6 Multimedia · advanced check

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Advanced check. This is a file-internals rule. It is hidden from the standard report view and generally indicates a problem with the tool that produced the PDF rather than something an author did.

Why it matters#

Audio/video annotations without alt text are inaccessible to deaf users (audio) or blind users (video).

What you will see#

A media clip data dictionary has no Alt entry describing the clip.

How to fix#

Add an Alt entry to the media clip data dictionary: an array of language/description pairs, e.g. ['en-US', 'Narrated overview of quarterly results'], with non-empty description text for the audio or video content.

Step-by-step guide#

1. Locate the media clip data dictionary the same way as for MEDIA_CLIP_CT: follow the flagged annotation's action to the rendition dictionary, then to the media clip dictionary in its C entry.
2. Add an Alt entry: an array of language and description pairs - a language code such as en-US followed by a description string such as Narrated overview of quarterly results.
3. Make each description meaningful and non-empty - EQChecker fails Alt arrays whose text is empty or whitespace - and describe the audio or video content itself, not the file name.
4. No Acrobat Pro UI exposes media clip dictionaries: the producing application embedded the media without its Alt entry, and the only reliable fix is regenerating the file from its source with an export pipeline that writes the Alt entry, or re-embedding the media through Acrobat's rich media tools and re-checking.
5. Treat the Alt entry as identification only: provide captions or a transcript per WCAG for the media content itself where applicable.

Verify: Re-run the EQChecker scan in advanced mode; MEDIA_CLIP_ALT should pass.

Note: Advanced-only check. The requirement originates in PDF/UA-1; audio content without a text alternative is inaccessible to deaf users and video without description to blind users. The Alt array may hold several language pairs - the pair whose text is non-empty is what satisfies the check - and it complements, not replaces, the annotation-level Contents description.

WCAG success criteria#

1.2.1 Audio-only and Video-only (Prerecorded) — Level A#

Prerecorded audio-only content (a podcast, a recording) needs a text transcript, and prerecorded video-only content needs a transcript or audio description, so the information is available to people who cannot hear or see it.

Understanding 1.2.1

Standards#

This check contributes to the following standards:

PDF/UA WCAG A EN 301 549