24th September 2002 - Going, Going, Gone Digital - A BBC Radio Perspective on 'Hard Disk' Playout

On 24 September, we had a riveting presentation from Andy Baker, Head of Technology (Radio) of the BBC Technology Direction Group. While the topic of audio playout systems for radio is not new, this wasn't about vague possibilities, this was about real engineering, and on a grand scale. Andy started by making the point that radio now meant much more than audio. The Digital delivery platforms - DAB, DSAT and On-Line services - can deliver text, images, and HTML content, for example. Any new contender for playout management would therefore need to handle all these types of content in an organised, linked way.

The choice of Digital technology was perhaps obvious. Digits are really good at 'joining up' and synchronising audio with other material. Open standards such as BWAV, AES3, AES47 and the SMEF model are available to transport the audio and other data around the place predictably. What's more, you can (with the right systems) automate those really boring - but important - jobs such as music reporting. But digits present some problems of their own. Some fundamental strategic decisions need to be addressed at the beginning. One of the most fundamental is the fact that digital audio takes up a great deal of storage space. Some really clever people invented 'bit-rate reduction', but this doesn't necessarily solve the problem. Andy considered the broadcast path from origination to the transmitter. Programme acquisition can come from a wide variety of sources and could be both linear and bit-rate-reduced. Subsequent manipulation, using any of a range of techniques, cannot easily be done with data-compressed audio so a conversion to linear PCM will need to happen for these sources.

When it comes to the output end of the broadcast chain, the playout system itself currently takes feeds from a range of dedicated technologies - CD, CD-R, DAT, MD - but in the future described here, will be handled by the new playout system. However, subsequent distribution to DSAT, DAB or On-Line, will invariably use some form of data compression.

The fact that this chain is heterogenous makes it sensible to use linear digital coding for manipulation and playout. There will already be a minimum of two cascades - perhaps three if the distribution system also uses bit-rate reduced techniques. Using MPEG in the playout system as well would therefore result in a minimum of three (possibly four!) cascades of coding - and that's without including any copying between MD's via the console!! The effect of so many cascaded codecs of different types would mean that quality degradation could be real but unpredictable. In addition, MPEG playout would require transcoding giving rise to monitoring and quality control issues. Fortunately, the cost of fast storage and network bandwidth is falling rapidly so it was easy to make the decision for manipulation and playout to be linear.

The new playout project covers London, Birmingham and Manchester and seven BBC's radio networks; Radio 1, 1xtra, Radio 2, Radio 3, Radio 4, 6 Music, and NWZ.

It seemed difficult to please everybody; each of these radio networks had a different way of working, from continuity-run networks like Radios 3 & 4 to fully automated outputs like NWZ. Also, each radio network had different needs in terms of multimedia content - text, data, pictures. Generating this would be a huge drain on the production teams.

The fact that the current archive is locked in the vault hinders creative and business opportunities. Each piece of stored material is an asset waiting to be used again in some new context. Choices made for digital playout hold the key to a more useful digital archive. In a similar manner, computers can be used to liberate busy staff from tedious admin tasks such as music and Programme as Broadcast (PasB) reports. Wouldn't it be nice if the digital playout system did it for you?

When comparing the emerging requirements with existing equipment, a blunt reality became apparent. Much existing broadcast audio equipment is now effectively obsolete - in the sense that it's not made any more - and much of it can't do multimedia.

Digital playout would need to be engineered as a new project.

First big question would one system do for all? It seemed a tall order, but "all radio networks are the same - honest!" says Andy. They tend to comprise "predictable long bits with anarchic short bits in between" .

Functionally the system needed to be resilient; if a serious problem arose, a show should be able to evacuate to any other area and carry on. Data should be stored across all user sites for speed of access and safety.

System operation should be flexible but consistent all staff should be able to use it; there should be just one training course and one set of manuals. And the operation of the system must be economical.

The users were involved from the start. This consultation enabled the requirement to be scoped - just what the heck do we want it to do? Ultimately, this led to a specification document. In reality, Andy noted, it's not a Specification Document in the old-fashioned sense but it is used to benchmark off-the-shelf systems and helps to concentrate the mind on the realities.

There's a lot of homework to do before you can approach the market, Andy observed. You need to know clearly what you want, and why. You need to know what everyone else is doing, which means checking out technologies at exhibitions such as AES and IBC and visiting other users to learn from their experiences. You need to know what the market has to offer, where the market is going and to spot the trends and dead ends.

After an extensive tendering process the BBC were able to select a supplier that was able to deliver a system to the scale they required and which continued to be scalable for the future. It was a resilient solution - including an Operating System suitable for the task (Open VMS). The system integrated with their business systems and it was the most cost effective solution. The BBC selected VCS with their dira! playout system. VCS are a systems company with experience in many different areas including satellite weather systems, space industry ground control systems, radio and media. These are all real-time systems with a high penalty for unreliability.

The chosen system comprises a set of distributed, interconnected networks. Storage is duplicated in a number of physical sites. A Medianet linear audio network joins offices and studios.

Medianet is linked to the BBC Office IT network to contribute data-compressed browse-quality audio. There is no audio editing at normal office computers, however they do handle administrative tasks such as scheduling, music management, programme building, scripts and reporting. In the studio, Medianet provides the connection to the on-air server which is running the Open VMS operating system. Each studio will typically contain an on-air screen showing what's currently being played out. A multi-use screen can be selected to display scripts, databases and scheduler or a local desktop computer. A third touch-screen provides a software-base cart player running on Windows 2000.

The first phase of the new playout system will

• Upload and record audio
• Edit audio
• Add broadcast text and scripts
• Schedule programmes using playlists from 'Selector'
• Update 'Selector' with as runs for rotation
• Enable widespread viewing and listening via a browser
• Play out audio items and associated text items, appropriately timed
• Automate layout
• Make material available online
• Support music reporting of whole items
• Automate digital archiving.

Andy concluded by observing that technology is only right if people can use it, but that people couldn't stay in the past. It was important to involve users from day one. In terms of economy, this sort of approach may not save you money, but it did give more bangs per buck.

Mark Yonge