Audio Description Types
Audio description (AD) provides narrated visual information for blind and low-vision viewers, ensuring equal access to video content as required under ADA Title II and Section 508 for effective communication.
When you request audio descriptions in Echo Labs, you can now choose between three delivery methods -- at no cost difference. This choice affects how descriptions integrate with your video's pacing and determines whether the final runtime extends.
Standard Audio Description
Standard AD fits descriptions into natural pauses in your video's audio track. The narrator speaks during silent moments—between sentences, during scene transitions, or when no critical audio is present.
The video plays continuously without pausing. Descriptions overlay during gaps, and the final video duration remains unchanged.
WCAG Compliance
Standard AD satisfies WCAG 2.2 Level AA (Success Criterion 1.2.5) when the existing pauses are sufficient to convey all essential visual information.
When to Use Standard
Standard works well for:
Interviews or discussions with natural conversational pauses and infrequent visual information
Narrative videos where speakers pause between points
Content where visual elements are simple and describable in brief phrases
Documentary-style content with breathing room in the audio
When Standard Isn't Enough
If your video includes complex visual information that can't be described within available pauses—like detailed charts, rapid demonstrations, or dense visual sequences—standard AD will omit critical information. This creates an accessibility gap where sighted and non-sighted viewers receive unequal access to content.
For such content, extended audio description would be necessary to maintain compliance.
Extended Audio Description
Extended AD pauses the video when necessary to provide complete descriptions of visual content. The video freezes, the narrator delivers the full description, then playback resumes.
This extends the total runtime but ensures no visual information is lost due to timing constraints.
WCAG Compliance
Extended AD satisfies WCAG 2.2 Level AAA (Success Criterion 1.2.7) and is required when standard AD cannot adequately convey essential visual information due to insufficient pauses.
When Extended Is Required
Use extended AD for:
Lectures with visual aids —Professors teaching with slides, diagrams, or charts often don't pause long enough to describe complex visuals. Extended AD ensures students receive complete information about graphs, equations, anatomical diagrams, or other instructional visuals.
Laboratory demonstrations —Procedures shown visually (pipetting techniques, equipment setup, experimental observations) require detailed description that typically exceeds available pauses.
Fast-paced presentations —Conference talks or rapid-fire presentations where speakers move quickly between visual elements.
Visual-heavy content —Art history lectures, architecture walkthroughs, medical imaging reviews, or any content where the visual component carries substantial informational weight.
Auto AD Mode (Recommended)
Auto mode analyzes your video to determine the optimal approach, combining both standard and extended descriptions to minimize interruptions while ensuring complete access to visual information.
How Auto Works
The Echo Labs system performs multiple algorithmic passes on your video. Some of these passes include:
1. Dialogue analysis —Identifies all natural pauses and measures their duration
2. Visual complexity assessment —Analyzes scene changes, on-screen text, visual demonstrations, and informational density
3. Description requirements —Determines what visual information needs description and how long those descriptions require
4. Optimal insertion strategy —Maps descriptions to available pauses. When a description fits naturally, we use standard AD. When pauses are insufficient for complete description, we use extended AD for that specific moment.
The result: a hybrid approach that uses standard AD wherever possible and extended AD only when necessary. This minimizes interruptions while maintaining complete visual information transfer.
Why Auto Is Preferred
Blind and low-vision users consistently prefer Auto for educational content. It balances two competing needs:
Minimize disruption —Too many pauses can fragment comprehension and extend runtime unnecessarily
Ensure completeness —Missing visual information violates the principle of equivalent access
Smart Omission
Our system never includes descriptions when they're not necessary. If a professor verbally describes a chart while showing it, we don't duplicate that description. If visual elements are purely decorative or don't add informational content, we omit description as well.
This intelligence ensures AD enhances accessibility without adding redundancy or unnecessary narration.
Making Your Choice
When uploading videos, you can select your audio description type in the upload modal.
