By Alfred Hermida BBC News Online technology staff

Imagine if every time you pressed a button on your TV remote control, information was kept to record your viewing habits.

This is what a California court has ordered the hi-tech consumer electronics company SonicBlue to do with people who have bought its ReplayTV 4000 digital video recorder.

The company has now formally requested an immediate reversal of the order, describing it as "breathtaking and unprecedented".

SonicBlue said the court order "violates consumers' privacy rights, including those guaranteed by the First and Fourth Amendments".

Copyright battle

The court order is part of the wider struggle between the entertainment and technology industries over how digital advances are changing the way people consume films, TV and music.

ReplayTV 4000 features

Automatically skips ads Sends recorded shows over the net Stores up to 320 hours of TV Streams video over a home network

The plaintiffs in this case include the film studios Paramount, Universal and Disney, as well as the TV networks CBS, ABC and NBC.

Lawyers of the media companies say they need this information to find out the extent to which the ReplayTV 4000 allows customers to copy and share TV shows and films.

Under the court order, the information collected would record whether the consumer skipped the ads, watched the same show more than once or deleted the programme from the unit.

SonicBlue's ReplayTV 4000 went on sale in the US last September. It works like a normal VCR but it records shows to a hard drive, rather than video tape.

Like other personal video recorders, the machine can pause and instantly replay live television or it can skip the ad breaks.

The unit also has a high-speed internet port that allows users to share film files.

The court's order is highly troubling

Consumer Electronics Association

"We've done a lot of research in the past that shows that once someone had a ReplayTV, the number of hours of TV they watched actually went up," SonicBlue's Jonathan King told the BBC programme, Go Digital.

"So they're going to be watching more TV and more quality TV, not just the fluff that just comes up."

But the entertainment industry is uneasy about the range of features offered by the player.

It argues these features threaten to deprive it of the revenues needed to pay for new shows, since the machines allow ads to be cut out and premium shows on subscription services to be forwarded to non-subscribers.

One senior television executive has gone so far as to equate skipping the ads with theft.

But SonicBlue argues it is not doing anything illegal.

"We're not deleting the commercial," insisted SonicBlue's Lanc Ohara.

"We're just giving the consumer the ability to not watch the commercial. If they want to see them, they can," he said.

'Invasion of piracy'

Privacy groups and consumer electronics firms are up in arms over the ruling, which effectively orders SonicBlue to spy on thousands of customers to see if they are breaking copyright law.

"The court's order is highly troubling," said the trade body, the Consumer Electronics Association, in a statement.

"It forces SonicBlue to violate the trust of its customers and commit an incredible invasion of privacy."

SonicBlue has been given until 24 June to impose a tracking system on its customers.

It is appealing against the order, arguing it will be forced to redesign its machine for the express purpose of collecting information to be used against it.

It says the changes will cost $400,000 and take four months to implement.

Earlier versions of the Replay recorder and similar digital devices from Tivo, which allow users to copy TV shows and keep them for later viewing, have been on sale for several years.