Complete Guide to Video & Audio Content Accessibility: Subtitles, Captions, and Audio Descriptions

Summary

• Differences and roles of subtitles/captions and audio descriptions
• Explanation of WCAG 2.1 AA level requirements
• Workflow from creating to implementing captions
• Concrete steps for introducing audio descriptions
• Tools & sample code for practitioners

1. Why Video & Audio Accessibility Is Necessary

On today’s web, video and audio content are key tools for user engagement. However, for people with hearing or visual impairments, simply “seeing” or “hearing” can be a major barrier.

• Bridging the Information Gap: Adding subtitles/captions converts audio into text, making content accessible to those with hearing limitations.
• Improving Comprehension & Learning: Subtitles also serve as an aid for non-native speakers and learners.
• Legal Compliance & Brand Value: WCAG 2.1 AA compliance is the baseline required in many regions. Accessible video demonstrates a company’s CSR.

Audience: Video producers, marketing teams, e-learning developers
Accessibility Level: WCAG 2.1 AA (captions required, audio descriptions recommended)

2. Basics of Subtitles vs. Captions & WCAG Requirements

2.1 Subtitles vs. Captions

• Subtitles: Primarily translate spoken dialogue for viewers who can hear, often offered in multiple languages.
• Captions (Closed Captions): Transcribe speech, sound effects, and speaker IDs—specifically designed for people with hearing impairments.

2.2 WCAG 2.1 AA Success Criteria

• 1.2.2 Captions (Prerecorded): Prerecorded video must include captions (mandatory).
• 1.2.4 Captions (Live): Provide real-time captions for live broadcasts (where possible).
• 1.2.6 Sign Language Alternative: Using sign-language interpretation alongside captions moves toward AAA compliance.

3. Workflow for Creating Subtitles/Captions

1. Transcription
   • Accurately convert audio to text, tagging speakers and sound effects.
2. Add Timecodes
   • Use the format [00:00:05.000 --> 00:00:08.500] to specify display start/end times.
3. File Format
   • Use the web-standard WebVTT (.vtt).
4. Quality Check
   • Play the video alongside captions and correct timing or typos.
5. Implementation

   <video controls>
     <source src="movie.mp4" type="video/mp4">
     <track kind="captions" src="captions.vtt" srclang="ja" label="Japanese Captions" default>
   </video>
   

6. Multi-language Support
   • Add additional tracks (e.g. srclang="en") so users can choose their language.

4. Key Steps to Introduce Audio Descriptions (AD)

Audio descriptions narrate visual content for viewers with visual impairments. WCAG 2.1 AA recommends AD under 1.2.5 Audio Description.

1. Script Development
   • Insert narration during silent intervals (between dialogue and sound effects).
2. Record Narration
   • Hire a professional narrator or record in-house.
3. Integrate into Video
   • Provide as a Separate Track so users can toggle between the AD and standard version.

   <video controls>
     <source src="movie_ad.mp4" type="video/mp4">
     <track kind="descriptions" src="descriptions.vtt" srclang="ja" label="Audio Descriptions">
   </video>
   

4. UI Design
   • Add an “AD On/Off” button on the player, with full keyboard accessibility.

5. Practitioner Tools & Automation

6. Case Study: E-Learning Platform Implementation

• Background: An online learning service enhanced accessibility by adding captions and AD.
• Approach:
  1. Bulk-added captions to existing content.
  2. Created and offered AD for ten core lectures.
• Results:
  • 1.8× increase in access by learners with hearing impairments
  • 92% positive feedback on “improved understanding” from visually impaired learners
  • 12% increase in average course completion rates

7. Maintaining Quality with Continuous PDCA

1. Plan: Define accessibility policy and KPIs (e.g., 95% caption accuracy).
2. Do: Produce captions/AD concurrently with new content.
3. Check: Conduct regular automated tests and user testing.
4. Act: Iterate on feedback and error reports to improve quality.

8. Who Benefits & Key Advantages

• Content Creators: Standardized workflows streamline subtitle/AD production.
• Marketers: Accessible content builds brand trust.
• Educators/Trainers: Better learning outcomes and engagement across diverse learners.
• Learners/Viewers with Disabilities: Equal information access supports self-learning and expression.

9. Conclusion: Balancing “Empathy” and “Technique” in AV Accessibility

• Use subtitles/captions to visualize audio for those with hearing impairments.
• Use audio descriptions to narrate visuals for those with visual impairments.
• Base implementation on WCAG 2.1 AA, aiming for AAA (e.g., sign-language options) when possible.
• Employ the right tools and a PDCA cycle to continuously enhance quality and reach all users.

We hope this guide helps you add thoughtful captions and audio descriptions to your video and audio content, creating a more inclusive web experience.