Editor's note: this is a joint posting from: Mark Kortekaas (BBC Audio & Music), Ian Myatt (BBC Nations & Regions) and Karl Kathuria (BBC World Service)

At BBC Radio we try to deliver the best experience for users of our streaming services. We constantly review our services to make sure they deliver 'public value'. The four drivers of public value are: Reach, Quality, Impact and Value.

When streaming services are evaluated against these measures, we take into account where different formats might need to be implemented, evolved or deprecated.

The streaming service provided in RealMedia format has been with us at the BBC since 1996. At the time it was the best option available, but more recently alternative methods of delivery have become just as important. These include Windows Media and Flash.

When evaluating services with our public value tests, which includes the costs of the services, we came to the decision that RealMedia was something we needed to phase out.

The actions to phase out RealMedia are broken down as follows:

National networks - e.g. Radio 2, Radio 6Music, Asian Network, etc

Nations - e.g. BBC Radio Scotland , BBC Radio Wales, etc

Local Radio - e.g. BBC Cumbria, BBC Bristol, etc

WorldService - the English language streaming service in iPlayer only - international World Service streams are unaffected.

It was clear that we could easily plan for a migration period for National networks during which RealMedia and alternatives will be available and allow for our audience and third-parties to make changes in a reasonable period.

So we'll be phasing out RealMedia by 30 March, 2010 for National networks.

In order to improve the experience in the BBC iPlayer web interface, we'll change the lower bandwidth option from its current RealMedia offering to a new Flash offering at 48kbps. We hope for this to be completed in October.

The legacy RealMedia streams will continue to exist on our systems until the March deadline, so that it gives those who still use them time to migrate to using the alternative:

Windows Media for Live streams - available globally for these services

Windows Media for Listen Again streams - will phase in over the next few months and be available globally.

The technology used for Nations and Local Radio services is more restrictive and a more difficult decision had to be made. A migration period would not have been possible without a significant increase in equipment which could not be justified. We had to make the unfortunate decision to switch off RealMedia as we simply could not offer both RealMedia and Windows Media at the same time.

In addition to the disruption caused to the Listen Live services, an unforeseen dependency means that the Listen Again service in Windows Media won't be operational until November.

Due to differences in production, World Service live and on-demand streams will continue to be available in Flash, RealMedia and Windows Media formats. However, if you access our content through BBC iPlayer it will only be available in Flash. Links to RealMedia and Windows Media versions of our programmes will be available from bbcworldservice.com.

Mark Kortekaas is Future Media Controller, A&M and Mobile Media