• Success Criterion 1.2.4
  • Conformance level AA

Live Auto-Captions Too Inaccurate for Technical Content

1.2.4 — Captions (Live)

Scenario

Setting

A recipe site's ingredient list

What’s wrong

Live auto-generated (speech recognition) captions with accuracy too low for comprehension in the domain (names, technical terms) and no correction.

Example 

<div class="live-cooking-stream">
  <video src="live://chef-demo-feed" autoplay controls>
    <track kind="captions" src="live://chef-demo-asr-captions" srclang="en" label="Auto captions">
  </video>
</div>
<!-- Live ASR renders: "add two cups of keen wah and a tea spoon of
     zap tar spice blend" for "quinoa" and "za'atar" -->

Why it matters

A deaf home cook following the live demo can't tell the auto-captions mean "quinoa" and "za'atar," so they either guess the ingredients wrong or give up following along.

How to test

Compare live auto-generated captions to a 30-second sample of speech: heavy errors in names/technical terms with no correction mean it fails.

How to fix

For live events full of specialized vocabulary, prime the recognition engine's dictionary in advance or use a captioner who knows the domain.

<div class="live-cooking-stream">
  <video src="live://chef-demo-feed" autoplay controls>
    <track kind="captions" src="live://chef-demo-asr-captions" srclang="en" label="Auto captions">
  </video>
</div>
<!-- A custom vocabulary of recipe terms (quinoa, za'atar, etc.) is
     preloaded into the recognition engine before going live -->

Outcome

A deaf home cook reads the correct ingredient names live and follows the recipe without pausing to guess.

Who is affected

Deaf and hard-of-hearing viewers relying entirely on the caption feed get nonsense words for exactly the ingredient names they need to shop for.

Learn more

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