The BBC Trust has given final approval for the iPlayer, the corporation's proposed online seven-day catch-up TV service.

After the trust's first application of its new public value test, approval was granted with two further amendments proposed by the trust in addition to BBC management's original plans.

The trust has now said that no more than 15% of the content on the iPlayer can be available for so-called "series stacking", where users can download multiple episodes of a particular TV series.

Only certain types of programming will be offered this way, such as limited-run drama series. But the iPlayer will allow users to stack up previous episodes for the duration of the series, not just seven days after it aired. All other content on the iPlayer will be less than seven days old.

The second change is that after noting what it described as "strong public demand", the trust will audit the BBC's progress in making the iPlayer platform neutral.

BBC management originally proposed that the iPlayer would run only on Microsoft's Windows operating system and the Windows Media Player 10 because it wanted to use Microsoft digital-rights management technology.

Management also told the trust it would be unworkable to make the service available on other operating systems, such as Apple and Linux, within two years.

However, the trust will now audit the BBC's progress on this issue every six months and will publish its findings. The iPlayer project will cost £132m over five years.

Diane Coyle, BBC trustee and chair of the trust's public value test steering group, said: "The Trust is satisfied that the BBC's new on-demand services will create significant public value with limited market impact. We have therefore given our final approval for the services to be launched. "When considering the potential market impact of new service applications from the BBC, we must focus primarily on the effect on consumers who enjoy the choice offered by content and services beyond those provided by the BBC."

Other on-demand services given the go-ahead by the trust today include audio podcasts, simulcast TV online and seven-day catch-up TV via cable.

Cable catch-up will function under the same series-stacking conditions as iPlayer content, and podcasts will be used for all audio that does not include rights-protected material, such as music recordings.

Classical music and audio book material should not be included in on-demand services, the trust decided, because it was felt that such a service would impact too heavily on the market.

BBC director general Mark Thompson welcomed the trust's decision and said the public value test had been "extremely rigorous and exhaustive".

"This is a significant decision as the new on-demand proposals are at the heart of the BBC's Creative Future," he said. "However, we disagree with the trust's decision to exclude classical music podcasts from the proposal: our research suggests that classical music audiences would wish to download classical music programmes from the BBC and to listen to them on their terms, free at the point of use."

The trust said it had received an unprecedented 10,608 submissions over the iPlayer proposals, 10,500 of which were from members of the public. Most submissions supported the plans, the trust added.

More than 85% of respondents said it was important for catch-up services to be available on software other than Microsoft, and nearly 80% said a series-stacking feature should be included. Only a quarter said that they felt parental controls were necessary.

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