GWR Group PLC are one of the largest and most technology driven radio groups in the UK, if not the world. Over the last year, they have put into place an IP based delivery system which is changing the way that they distribute live audio and data around their radio stations. As a small part of this system, they commissioned Sonifex to design and manufacture a fail-safe switchover unit, given the acronym of DAMN (Data and Audio Monitoring Node). This was to work with their recently developed BLAST (Broadcast Live Audio STream) system.
The old programme distribution system consisted of 2 carriers on the Sirius satellite, one the FM Mix network and the other Classic Gold. At each of 30 receiving sites there were 2 satellite receivers. Whilst this system worked ok, it was expensive, inflexible and was reliant on getting a signal to the uplink sites. Additionally, satellite links were subject to some weather related failures.
Project Manager Tim Lowther said "One of the problems of satellite uplinks is that they are affected by changing climatic conditions - they can suffer from rain-fade, snow drop-outs and even sun-outs when the sun is in a certain position relative to the dish. If it happens at the downlink then it can be a problem, but at the uplink it means that we lose the whole transmission. WANs are much more stable and resilient now."
GWR invested in a new generation IP network supplied by Thus, with a view to being able to stream live, broadcast quality audio between stations. A bespoke software system (BLAST) was developed in order to eliminate the need for satellite links.
It was Group Technology Infrastructure Manager Vincent Bourne who instigated the project and liaised with Thus over the implementation. He commented "It's a new generation of audio distribution system that we're creating. The system is a world first for a live broadcast network. Many people are using IP codecs, but tend to use dedicated networks. Ours is a fully shared infrastructure, carrying Voice, Data & Broadcast traffic. The delivery of the new network is the realisation of our long-held vision for the impact a modern data network can bring to the Radio business. It gives us the capability to broadcast live from any site to any site at the drop of a hat.”
At each LRG (Local Radio Group) station in the GWR network are 2 standard PC's, main and reserve, containing broadcast quality sound-cards providing balanced audio outputs. On each PC, GWR software decodes the audio in 2 enhanced apt-x streams with the ability to work at different bandwidths, so if the bandwidth on the network drops, e.g. if a circuit fails, the broadcast can automatically drop to a lower, but still acceptable, bandwidth. The 2 PC's have audio, alarm and RS232 connections to the Sonifex DAMN box, which outputs the two stereo audio streams and two RS232 feeds to the IP stream. Software installed on the PCs sends status information, via the parallel port, to the DAMN box. This status information includes a Heartbeat (a 2 second pulse), a major alarm (loss of audio stream, or power fail) and a minor alarm (lower quality audio stream being used).
The DAMN unit can be controlled locally; via momentary switches on the front panel, or remotely, using remote switch inputs on a d-type connector on the rear panel of the unit. This remote connector also supplies relay contacts for alarm indicators.
GWR Infrastructure Manager Vincent Bourne commented : "With an increased group focus on disaster recovery, the DAMN box allows us to have a hot standby, with a dynamic switchover so that any loss of content should be almost imperceptible for the listeners. Historically, we had 1 satellite link per service, so if it failed, we lost the link - now we have dual redundancy. Additionally, the changeover unit allows us to carry out software upgrades on our PC systems by manually switching the audio streams to the other PC during the upgrade."
Tim Lowther added "I knew of Sonifex's design and manufacturing capabilities and they were able to produce the DAMN boxes to our specification on time and within budget. We're very happy with the outcome."
The units were put into operation at 30 stations around the UK in early February 2004 and have been running without failure since then. Currently multicast streams are being generated at Bristol and Dunstable, but the potential is to be able to generate them anywhere.
