Test tool automatically detects rogue pixels

August 06, 2012 // By Nick Flaherty
A pixel analyser developed by Cambridge test equipment maker Cel-Soft allows television cameras and programme content to be checked prior to acceptance or for post-production analysis.

Pixel-Probe allows HD images to be checked for rogue pixels automatically rather than eye in a range of different conditions for post-production and boradcast systems.
"Broadcasters have hitherto had little option but to perform acceptance tests visually," said Robin Palmer, managing director of Cel-Soft. "Detecting rogue pixels by eye among the 6 million RGB elements in images from HD cameras is almost impossible.
"Manufacturers of high-quality cameras pre-calibrate each sensor, mapping the location of any defect," he said. "An offending pixel can then be masked by digitally averaging the signals from the four or eight neighbouring pixels. Cheaper cameras use no such masking. In any case, once a camera gets into the studio or the field, pixel defects can appear at any time as a result of age or temperature. Dust on the sensor or optics can be another problem. An uncorrected pixel error can show as a coloured or black dot. In single-sensor cameras, it can appear as tiny cross because of the way the pixels are spatially sampled.
"Our Pixel-Probe algorithm automatically generates a statistical log of every pixel, allowing a check to be made of relative response. It can then work out, over a short period of fluctuating footage from the camera, if any pixels are not working properly. Pixel-Probe can also identify pixels that have changed their behaviour since the previous time the camera was checked, or between different shots in post," he said.
"The increasing use of digital single-lens-reflex cameras for broadcast and even cinema production, along with other low-cost cameras, will make this sort of test process essential. Bigger and better high-resolution displays are also making uncorrected pixel defects more obvious to television viewers."
Pixel-Probe is fully compatible with Cel-Soft's Reel-Check SoloQC live source or file analyser and Cel-Scope 3D real-time stereoscopic test and measurement system and will be launched at the IBC show in September.
www.cel-soft.com