Video Accessibility Glossary
A semantic reference hub for technical terms, regulatory standards, and mathematical models used in video accessibility and Photosensitive Epilepsy (PSE) analysis.
A neurological condition where seizures are triggered by flashing or flickering lights, or by high-contrast visual patterns.
A web accessibility standard requiring that pages and video content do not flash more than three times per second, or that any faster flash is below defined safety thresholds.
The core rule under WCAG 2.3.1 stating that content must not contain more than three flashes in any one-second period.
The relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white.
A pair of opposing luminance transitions of 10% or more of reference luminance (or Michelson contrast of 1/17).
A transition to or from a saturated red state (R/(R+G+B) >= 0.8) with a CIE 1976 UCS chromaticity delta > 0.2.
Flash and Pattern Analyzer, the commercial broadcast gold standard tool mandated by Ofcom for photosensitive safety testing.
Photosensitive Epilepsy Analysis Tool, a free legacy desktop software tool developed by the Trace R&D Center for checking web videos.
The UK regulatory body for broadcasting, which mandates strict PSE compliance using the Harding FPA.
A compliance standard developed by the Trace R&D Center mapping to the 24Hz testing guidelines.
The Japanese broadcasting associations' standards for photosensitive safety in broadcast television.
The central field of view used by WCAG to calculate the spatial threshold of flashing content.
A unit of solid angle used to define the visual field area, where the critical flash threshold is 0.006 steradians (25% of a 10-degree visual field).
The quality of color characterized by its dominant wavelength and purity, independent of luminance.
Commission Internationale de l'Éclairage Uniform Chromaticity Scale, used to measure chromaticity differences for red flash detection.
Section of the Americans with Disabilities Act requiring state and local governments to make web content and videos accessible.
Legislation in the UK making it a criminal offense to send flashing images to trigger seizures in people with epilepsy.
A CSS media query used to detect if the user has requested the operating system to minimize non-essential motion.
The mathematical process of converting sRGB gamma-encoded color values into linear relative luminance values.
The ratio of the difference between peak and minimum luminance to their sum, used to evaluate flashes when the darker state is >= 80% reference luminance.
The time window (66 ms or less) within which a single transition must take place to be counted as part of a flash.