Image caption The average American watches five hours of TV a day, Google said

Search giant Google has launched a TV service that unites live television with the web.

The "smart TV" service allows people to search both live channels as well as content from websites such as YouTube.

Special TV sets - or normal TVs connected to a Google box - will also allow people to access the web and download applications.

The first TV sets will be produced by Sony and should be available in the Autumn.

"Video should be consumed on the biggest, brightest, best screen in your house - the television," said Rishi Chandra of the firm. "That's not the PC, or mobile."

He said that there were currently 4bn TV users worldwide and that around $70bn (£50bn) was spent annually on adverts in the US alone.

"There is no better medium to reach a wider and broader audience than TV," he said.

Google is great at organising information, both legal and illegal Dan Cryan

Google generates the lion's share of its revenue from selling web ads and many analysts speculate that its move into television is an extension of the business.

Dan Cryan, an analyst at Research Firm Screen Digest, said that television was a "very natural space" for Google.

"Its stated ambition is to organise the World's information, so why not move into it," he told BBC News.

He said that there had been several attempts to connect televisions to the internet in the past but none had been "terribly successful".

"Things have changed recently with an increasing number of higher quality web TV services available on TV sets."

'Mobile impact'

Google showed off the service at a launch event in San Francisco that was plagued by technical glitches.

So many people in the 5,000-strong audience were using the conference wi-fi that the demo ran into repeated problems.

Google finally had to ask people to disconnect their phones from the wireless network to free-up enough bandwidth.

The service is built around an onscreen search box, similar to Google's web offering, that allows people to search for content on live channels or the web.

Image caption Google have announced several products at the conference

Mr Chandra showed how searching for the television programme House brought up results from live channels as well as web services such as Hulu and Amazon.

"The TV becomes a natural extension of the web," he said. "You spend less time finding your favourite content and more time watching it."

The service streams shows from the web using Google's Chrome browser.

Mr Cryan said the approach opened up an "interesting question" about whether people would use the service to watch pirated content.

"Google is great at organising information, both legal and illegal," he said.

The browser also allows people to search non-video content from the web.

"We can make your TV into a games console, a photo viewer or a music player," Mr Chandra said.

The first television sets will be built by Sony, who will also build the service into a Blu-Ray DVD player. Set top boxes and peripherals will be built by Logitech, although the service can also be controlled from a mobile phone running Google's Android operating system.

The TVs and boxes will also use Android and will rely on an Intel microprocessor.

"We want to have the same impact on TV that the smartphone had on the mobile experience," said Mr Chandra.

Future battle

The firm has also used the conference to launch various initiatives, including an update to its Android operating system and an open source video project called WebM.

The WebM project will make the VP8 video codec, which it acquired when it bought On2 for $133m (£92m), open source.

Codecs are used to encode and decode web video. Various formats are currently competing to become the default standard for web video in the future.

Several web browser makers, including Mozilla, which makes Firefox, and Opera, have agreed to support Google's new format, which will be offered for free.

Another codec called H.264 has the support of Apple and Microsoft.

Whilst it will be free for the next five years, it is encumbered by patents and its owners MPEG LA plan to charge for its use.