Suranga Chandratillake is explaining why it is difficult for a computer to tell the difference between a border collie and a cow.

A machine can easily tell that an object in an image is a four-legged, black and white animal, he says; possibly also that it is standing in a field under the sky. (It 'sees' the green and blue.)

Beyond these basic recognitions of form, however, a computer's ability to interpret - and therefore 'read' - an image becomes more hazy. This is because humans' ability to interpret what they see relies on a process of contextualisation, or what Chandratillake calls 'reading visual clues' - something computers have so far been poor at imitating.

Blinkx, the company he runs, attempts to overcome these difficulties by teaching a computer to 'read' more signs in video - for instance by listening to what someone in a clip is saying, and observing any writing on the screen.

In relation to the cow example, then, "if the video is running on a site about milk production, it's more likely to be a cow."

This, he and many analysts believe, will be an increasingly important service because, despite an ever increasing amount of video content being posted online, search engines rifling through it for relevant clips have typically returned poor results.

"The internet has stopped being a place primarily orientated around text, and is now one where you find a lot of rich media - video in particular," Chandratillake, 29, says.

"The problem with it is that it's very messy and fragmented - anyone can put content up, and it's distributed across an extremely broad range of sites."

Blinkx 'spiders' - or 'watches' - all the web's video content, ascertains as best it can the meaning of each clip, and then stores this in an index which is trawled when somebody conducts a search on a Blinkx-powered engine.

The majority of these indexes will be scoured by internal search engines on video-rich sites - such as those of the television networks, though some general search engines, such as Ask's, now also use it for their video search service.

Blinkx's earnings come from sharing any advertising revenue generated by a site when it displays a clip found by Blinkx's engine.

The company raised £25 million when it listed on AIM after being spun off from Autonomy, the Cambridge-based software group, and so far has struck deals with more than 20 high-profile sites, including Real Player, Lycos and InfoSpace.

Surely the jewel in the crown, however, would be a partnership with Google?

"A Google deal would be great - you'd assume there'd be a lot of traffic - but it's not essential. Google is the biggest single source of search traffic, but there are many more searches done on non-search engine sites," he says, referring to internet searches on non-search-specific sites, which are known as "white label" products.

It's a gamble pegging everything to video search, especially seeing as the technology has a way to develop yet, but so far the analysts agree.

Citi has the company breaking even in 3 years, with predicted earnings of $60 million in 2010 - its third year of operation, up from the $4.4 million Chandratillake expects it will earn this year.

The focus in the short term is on growing the company's sales team. By the end of the year, the head count will nearly have doubled since the IPO - up from 27 to 50, the majority in sales, with a fresh injection of research and development talent expected in 2008.

How is he finding it being cast as one of the rising stars in Silicon Valley, a role with which many West Coast-based 20-somethings are now familiar?

"I know it sounds a bit cheesy but I feel I'm on a mission - born out of an obsession with technology - to change things and make them better, " he says.

And does he ever take time out?

"My big achievement this year was getting married," he jokes, "but it's true my interests have taken a back seat. My great love is the balalaika, a Russian folk instrument similar to a lute, or mandolin. One day, when this is over, I may take it up again."

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