SiteLint documentation and guidelines

Audio and video content need captions and subtitles

Description

WCAG 1.2.1 requires that prerecorded audio-only and video-only media provide alternatives to ensure all users can access the content. This accessibility requirement is fundamental for ensuring that multimedia content is perceivable by everyone, regardless of their abilities.

WCAG 1.2.1 mandates two main requirements:

  1. For prerecorded audio-only content: Provide a text alternative that captures all meaningful information.
  2. For prerecorded video-only content: Provide either a text alternative or an audio track describing the visual content.

Disabilities impacted

Visual impairments

  • Users who are blind or have low vision benefit from audio descriptions of video content.
  • Assistive technology can convert text alternatives to braille or screen reader output.
  • Parallel presentation allows simultaneous review of content for users with varying levels of vision.

Cognitive disabilities

  • Alternative formats help users process complex information.
  • Text-based alternatives support multiple learning styles.
  • Parallel presentation (text + audio) enhances comprehension.
  • Users can review content at their own pace.

Motor impairments

  • Text alternatives enable control through assistive technologies.
  • Users can navigate content using preferred input methods.
  • Reduced need for precise timing or coordination.

Why it matters

This requirement benefits users in several critical ways:

  • Makes information accessible through any sensory modality.
  • Supports future adaptations (symbols, sign language, simplified language).
  • Enables searching and repurposing of content.
  • Provides backup when primary format isn’t suitable.

Coding problems and solutions

Common coding problems

Missing alternative text

Incorrect example
<audio src="speech.mp3"></audio>
Correct example
<audio src="speech.mp3">
  <a href="speech-transcript.txt">Transcript</a>
</audio>

Incorrect implementation

Incorrect example
<video src="tutorial.mp4"></video>
Correct example
<video src="tutorial.mp4">
    <track kind="captions" srclang="en" src="captions.vtt" label="English">
</video>

How to fix it

Audio-only content

  • Provide text transcripts immediately after audio elements.
  • Include speaker identification and important sounds.
  • Ensure transcripts are complete and accurate.

Video-only content

  • Choose either text transcript or audio description.
  • Audio descriptions must capture all meaningful visual content.
  • Text transcripts should describe both visual and auditory information.

Known limitations

Technical constraints

  • Automatic captioning accuracy issues (60-70% accuracy rate).
  • Resource-intensive process for manual transcription.
  • Storage requirements for multiple format alternatives.

Implementation challenges

  • Synchronization difficulties between media and alternatives.
  • Language translation complexities.
  • Maintenance overhead for large media collections.

Resources

Rule

  • Rule ID: audio-video-captions.
  • Standard: Accessibility, WCAG, 1.2.1.