Harding test

The term Harding Test is generically understood to mean an automatic test for Photosensitive epilepsy (PSE) provocative image sequences in television content. This is properly known as a PSE Test since the publication of the Digital Production Partnership (DPP) technical requirements^[1] and the DPP PSE Devices^[2] document (in the UK) in October 2013.

The HardingFPA Flash and Pattern Analyser is one proprietary software solution that is used to analyse video content for flashing and stationary patterns which may cause harm to those who suffer from photosensitive epilepsy. It is an implementation of the guidelines set by Ofcom in the UK. It is available in both tape-based and file-based versions, allowing video streams from SDI, Composite, Component, HDMI, and files to all be analysed, in resolutions up to 1080i. Versions for both Microsoft Windows and Apple Mac OS X are available. There are other manufacturers of similar and different solutions now available which are also approved on the DPP Devices list.

Photosensitive epilepsy

Photosensitive epilepsy affects approximately one in four thousand people and is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights, bold regular patterns, or regular moving patterns. In 1993, an advert for Pot Noodles induced seizures in 3 people, leading to the ITC introducing these guidelines. Similarly, in Japan during 1997, an episode of the children's cartoon 'Pokémon', Dennō Senshi Porygon triggered over 650 admissions to hospital leading to the episode being banned from television worldwide. More recently, 18 viewers "reported ill effects" while watching a promotional film for the London 2012 Olympics.^[3]

Testing procedures

The algorithms behind the Harding test itself were first developed by Cambridge Research Systems Ltd. and are based on research by Professor Graham Harding.^[4] All HardingFPA products implement the same guidelines. Other manufacturers products broadly do the same.

The software is currently used by many television stations in the UK to check for compliance with these guidelines. If a programme fails, it usually means re-editing the offending scenes. Normally this can be rectified by reducing the number of flashes in the scene and/or reducing the intensity of colours (most notably saturated red). After re-editing the problem areas, the entire programme has to be re-tested in order to obtain a HardingFPA certificate.

References

Harding GFA and Harding PF Photosensitive epilesy and image safety. Applied Ergonomics 41 (2010) 504-508