In an era replete with fake news stories, you might expect video evidence to provide a clearer picture of the truth. You'd be wrong, according to Google engineer Supasorn Suwajanakorn - who has developed a tool which, fed with the right input, can create a realistic fake video that mimics the way a person talks by closely observing existing footage of their mouth and teeth to create the perfect lip-sync. Like any technology, it has great potential for both good and mischief. Suwajanakorn is therefore also working with the AI Foundation on a "Reality Defender" app that would run automatically in web browsers to spot and flag fake pictures or videos.

"I let a computer watch 14 hours of pure Obama video, and synthesized him talking," Suwajanakorn said while sharing his shockingly convincing work at the TED Conference in Vancouver Wednesday. Such technology could be used to create virtual versions of those who have passed - grandparents could be asked for advice; actors returned to the screen; great teachers give lessons, or authors read their works aloud, according to Suwajanakorn.

He noted a New Dimensions in Testimony project that lets people have conversations with holograms of Holocaust survivors.

"These results seemed intriguing, but at the same time troubling; it concerns me, the potential for misuse," he said.

"So, I am also working on countermeasure technology to detect fake images and video." He worried, for example, that war could be triggered by bogus video of a world leader announcing a nuclear strike.