Abandoned luggage and unexpected crowds - real-time cameras will use artificial intelligence (AI) to detect suspicious activity on the streets of Paris during next summer's Olympics. But civil rights groups say the technology is a threat to civil liberties, as the BBC's Hugh Schofield reports.
"We are not China; we do not want to be Big Brother," says François Mattens, whose Paris-based AI company is bidding for part of the Olympics video surveillance contract.
Under a recent law, police will be able to use CCTV algorithms to pick up anomalies such as crowd rushes, fights or unattended bags.
The law explicitly rules out using facial recognition technology, as adopted by China, for example, in order to trace "suspicious" individuals.
But opponents say it is a thin end of the wedge. Even though the experimental period allowed by the law ends in March 2025, they fear the French government's real aim is to make the new security provisions permanent.
"We've seen this before at previous Olympic Games like in Japan, Brazil and Greece. What were supposed to be special security arrangements for the special circumstances of the games, ended up being normalised," says Noémie Levain, of the digital rights campaign group La Quadrature du Net (Squaring the Web).
A version of the new AI security system is already in place in some police stations around France. One of the pioneers is the southern Paris suburb of Massy.
"Around the town we have 250 security cameras - far too many for our team of four to monitor," says Massy's mayor Nicolas Samsoen.
"So the AI device monitors all the cameras. And when it sees something it's been told to look out for - like a sudden grouping of people - it raises an alert.
"It's then up to the humans - the police officers - to examine the situation and see what should be the appropriate action. Maybe it's something serious, maybe it's not.
"The important thing is that it's humans who make the ultimate decision about how to react - not the computer. The algorithm is empowering humans.
As a test, we abandoned a piece of luggage on the street not far from the police station. Thirty seconds later the alarm was raised and CCTV footage of the suitcase popped up on the control room screen.
Previously of course the algorithm has had to be taught what an abandoned piece of luggage looks like - which is where the AI comes in. The developers have fed the programme a massive bank of different images of lone bags on the street - a bank which continues to grow as more images accumulate.
Crucially though, this "learning" process does not happen at the client interface but only in the "back-office" at the developers. Massy police station has bought a self-standing product which monitors the cameras, but cannot itself acquire new knowledge.
Detecting unattended luggage is a relatively easy task. Much harder might be spotting a person on the ground in a crowd; or seeing the lump in a person's clothes that is a concealed weapon; or differentiating between the beginning of a fight and an innocent temporary increase in crowd density.
A French start-up specialising in computer vision software, the XXII group, is waiting for further specifications from the French government before fine-tuning their bid for part of the Olympics video surveillance contract.
"We expect the government to want the AI to be able to detect fire, fighting, people on the ground and abandoned luggage," says XXII's François Mattens. "But they need to get their act together.
"In theory the new systems are supposed to be in place for the Rugby World Cup [in France] in September. But that is absolutely out of the question. It is all going to take a lot of time to put in place."
We see it as just as scary as what is happening in China
François Mattens and other developers are alive to the criticism that they are enabling unacceptable levels of state surveillance. But they insist on the safeguards.
"We will not - and cannot by law - provide facial recognition, so this is a wholly different operation from what you see in China," he says.
"What makes us attractive is that we provide security, but within the framework of the law and ethics."
But according to digital rights activist Noémie Levain, this is only a "narrative" that developers are using to sell their product - knowing full well that the government will almost certainly favour French companies over foreign firms when it comes to awarding the Olympics contracts.
"They say it makes all the difference that here there will be no facial recognition. We say it is essentially the same," she says.
"AI video monitoring is a surveillance tool which allows the state to analyse our bodies, our behaviour, and decide whether it is normal or suspicious. Even without facial recognition, it enables mass control.
"We see it as just as scary as what is happening in China. It's the same principle of losing the right to be anonymous, the right to act how we want to act in public, the right not to be watched."
This week BBC News is focussing on AI, how the technology affects our lives and what impacts it may have in the near future.