Capital Radio Network's Eleven Studio Centres
BBC Scotland ATM Network (Line Up Feb/Mar 2003)
Audix Broadcast Announce the ANTS Control System
Capital Radio Network's Eleven Studio
Centres (AES -
Journal of the Audio Engineering Society - AES Standard Commitee
News - Volume 52 Number 5
AES47 broadband audio networks now interconnect the eleven
production sites of the Capital Radio Group throughout the UK.
From 1973, when it became one of the first two licensed
commercial stations on air, it has expanded by acquisition to
operate 22 stations throughout the UK and now broadcasts to over
half of the UK's adult population through five radio branded
networks.
Studio centres are located in London, Birmingham, Cardiff,
Oxford, Kent, Sussex, Hampshire, the North East, the North West,
the East Midlands, and Central Scotland. AES47 equipment from
Audix Broadcast is installed at all sites. Capital Radio Group
contracted telecoms provider Thus plc to install an ATM
infrastructure for audio between its production sites around the
UK, fanning out from its main base in London, and which also
carries an Internet Protocol (IP) service. This project
illustrates the desire of broadcasters to exploit the potential
of broadband technology to carry audio and video in real time
together with e-mail and other IT data over the same network.
The new system was introduced during the summer of 2003 and was
initially used for general-purpose audio feeds. But it is now
fulfilling a much more fundamental role.
Peter Willison, Capital Radio Group's Technology Director, points
out that, beginning in March 2004, the AES47 network is being
used with Century Digital, a digital satellite radio station, to
provide a live link between production studios in Nottingham and
the uplink site in London. This link is operated continuously;
live-to-air.
With a few exceptions, each Capital site comprises at least two
radio stations-usually one for the FM service and one for the
Capital Gold station-and also provides DAB services. Richard
Bettison, Chief Engineer of Networks, explained that the project
has been undertaken to allow program material to be networked,
particularly between the Capital Gold stations. "If and
important band goes into our Newcastle station and does a good
interview, the only way for that to be distributed at the moment
is over ISDN, which would mean making 10 different calls,"
he said. "With ATM, all someone needs to do is place it into
the networked systems and the other stations can just drag and
drop it into their own computer screens."
It is the Capital Radio Group's policy to keep all audio linear
within the production and distribution chain so that non-linear
data compression coding will only be used for final transmission.
This simplifies many of the technical issues in the broadcast
chain and ensures a consistently high audio quality.
Ian Jennings is the managing director of Audix Broadcast, a
leading manufacturer of specialised digital audio equipment for
broadcasters. He observes that many of these products now use
integral ATM networking capabilities to great advantage. The
equipment supplied to Capital Group Radio comprises twelve
combined ATM (AES47) network and audio processing units, a server
and system management software suite, and a GPS Master Clock
system to synchronise each of Capital's sites to a common audio
reference to avoid the need for a sampling frequency conversion
even though the networked studio centres may be hundreds of miles
apart.
BBC Scotland ATM Network (Line Up Feb/Mar 2003) - The cost of fixed lines between broadcast centres has become prohibitive but high-tech IT solutions offer viable and cost-effective alternatives. COLIN MACNAB MIBS reports on a broadcast ATM system North of the Border.
Sometimes communicators seem to take a while to get around to communicating. However, when a broadcast service provider started communicating with a network service provider and a small broadcast equipment manufacturer, the results were very impressive, and highlight a very interesting path for the future of the industry!
The particular case in point is that of a recent installation in BBC Scotland of Audix Broadcast's new Gateway system. This enables the transmission of full rate digital audio over a standard ATM telecoms network, and the current implementation provides eight stereo circuits between Glasgow and Edinburgh. Although a digital replacement for conventional land-lines may not seem that exciting, this is the broadcaster's first step in a very powerful technology which is set to become an everyday tool. Indeed, work is already in progress to apply similar techniques to an ATM network for Broadcasting House in London.
ATM
This particular communications technology – ATM, short for Asynchronous Transfer Mode – is something which has been used by telecoms companies world-wide for some time. It is a fully scalable technology for the transfer of data between locations, with the ability to guarantee the integrity and security of specific pathways between users.
ATM works over a wide variety of different telecom infrastructures using fibre optic, copper, or satellite circuits, and at a various rates. The telecoms provider is not interested in what the data represents, but if you tell them where it has to go – and in the case of ATM when it has to get there – they will make it happen at a cost based on the required bit rate. In the case of the ATM system, it is not necessary to employ data reduction as the available data rate is more than sufficient for any application. There is also no significant time delay imposed on data passing through the network, and ATM protocols even allow the 'round trip time' of your data on your particular network to be measured.
ATM uses a 'cell relay' structure, in the parlance of some telecoms providers. The operating protocols basically divide the data to be transferred over the ATM network among a series of fixed length 'cells' for transmission. The protocols allow instructions along the lines of "transmit immediately", "make the next cell part of this transmission", and "pass other data, you are in the fast lane" to be included in the header of each cell. ("It sounds fine leaving here" does not yet appear to be an option!) The data packets are recombined when it is received, according to the header instructions.
Network Rates As already mentioned, ATM is already in widespread use, notably as the basis of most Internet 'backbone' systems. ATM network data rates are typically 2.5Gb/s on average, with a few 10Gb/s systems in limited use, while rates of 40Gb/s have been achieved in some trials. The operating protocols allow ATM to be used as a Wide Area Network, complete with data collisions slowing the whole system down (in the case of the Internet), or as the equivalent of a switched point to point connection system more recognisable and useful to broadcasters.
The scalable aspect of the ATM network means that any particular connection can be used for anything from a low data rate talkback channel to an uncompressed hi-def video service. Any required data rate can be made available up to the maximum of the particular network, and telecoms providers may offer 'Adaptable Bitrate Contracts' which essentially allow the broadcaster to pay for the data rate used on each specific occasion. However, it is also possible to establish the equivalent of a point to point circuit with a guaranteed bandwidth, if required.
Audix Broadcast In Scotland The telecoms company providing the ATM service to BBC Scotland is called Thus, but was formerly known as Scottish Telcom. In fact, the company started out as Scottish Power's telecom division, and it has a long history of innovative developments in sending 'stuff down wires'. The company also owns and runs the popular Demon Internet brand.
Interfacing between the ATM network and the BBC Scotland premises in Glasgow and Edinburgh are two Audix Broadcast Gateway units, providing four stereo outputs from, and four stereo inputs to, the ATM interface. Plug-in circuit cards determine the format of these audio interfaces, with both analogue (mic/line) and AES-EBU options being available. The latter can be specified with 20 or 24 bit resolution, and includes sample rate conversion facilities and an AES clock reference input.
Although not used in BBC Scotland, the Audix Broadcast ATM system can also be incorporated within Audix Broadcast’s digital studio mixers and newsroom workstations. This enables the creation of a completely integrated broadcast centre with various elements in other buildings or even on the opposite side of the world, connected only via ATM.
In the BBC Scotland installation, the audio signals are routed over the ATM network as a 25Mb/s data stream, through a pair of RJ45 connectors (one for the send and the other, receive). The Gateway unit also incorporates micro-controller and serial ports for external control and test purposes, but was being controlled in this application by a dedicated PC. The audio paths are integrated with the audio routing systems in BBC Glasgow and BBC Edinburgh. Thus the system is completely transparent in operation, and the users in Glasgow or Edinburgh see only sources and destinations on each centre’s internal router. The system functions as if there were fixed permanent lines between the two broadcast centres.
Daily Use
Steve Walker, Communications Developments Manager, BBC Scotland, is very pleased with the way the system is working and summed its operation up with: “Basically, it does what it says on the tin!” Of course, the trick of this particular ‘tin’ is that it joins the broadcast and IT worlds together to serve a new purpose. The level of integration also means that the whole thing is extremely cost-effective and, being based on a system that positively encourages expansion, the potential is enormous.
The cost of line rental can be a seriously large part of any broadcasting budget, but modern technologies - such as ATM - are offering cost effective alternatives without penalising audio quality. Small broadcasters, in particular, can take advantage of this and go directly to telecoms companies for data services where they are charged only for the data bandwidth actually used. Thus, ATM offers all broadcasters a robust, cost effective distribution system which avoids data reduction, coding incompatibilities, and timing delays inherent in many current systems. The Audix Broadcast Gateway system is the first practical installation of such technology in the UK, and it appears to be a roaring success for all concerned.
In days of old a
studio complex would be kitted out with impulse clocks, all
carefully maintained to ensure each studio displayed exactly the
same time as all the others, and agreed with the national timing
reference. Many installations still employ this kind of
time-keeping but it is relatively expensive and costly to
maintain. A very much cheaper alternative, now becoming quite
common, is the use of 'radio clocks' which automatically
synchronise themselves to a national MSF timing signal. However,
these clocks are often unreliable when installed in metal framed
buildings or in underground studios, and require their batteries
to be changed routinely, adding significantly to the running
costs and maintenance overheads.
Timing is not just limited to the clock on the wall these days
either. It is increasingly necessary to synchronise the timing of
automated computer play-out systems and, with the rapidly growing
use of ATM networking systems, to clock audio out at the far end
of a digital distribution chain at the same rate it was clocked
in! Another common requirement is to be able to trigger specific
events at pre-determined times — switching transmitters on
and off, or re-routing audio circuits between destinations, for
example.
The good news is that there is a very elegant and cost-effective
solution to hand! It comes from that diminutive but productive
British company, Audix Broadcast and is a further example of
another of their brilliant lights hidden under a bushel!
TickTock
The TickTock clock is beautifully elegant in its simplicity, yet
has been superbly engineered. This innovative system meets the
needs of any modern broadcasting operation and integrates every
imaginable requirement of a master timing system. It also has
numerous applications in many other industries where accurate
timing displays are required throughout an installation —
factories, hospitals, shopping centres, airports, railway
stations, banks, schools and so on.
The idea originally grew out of trying to find a way to make the
highly cost-effective radio clocks work more reliably in
difficult situations. Perhaps the most obvious solution is to
remote the MSF receiver from the clock itself to a location where
it could pick up a more reliable radio signal. However, that is
rather difficult to do as the reciever circuitry is embodied
within the clock mechansism, and it becomes prohibitively
expensive when repeated for a lot of clocks.
The solution developed by Audix Broadcast is to distribute a
common MSF signal around a broadcast centre on a simple screened
two-core cable, as a phantom radio signal superimposed on a DC
power supply. Each radio clock installed on the system requires a
simple modification which involves replacing the battery with a
circuit board, to which the incoming MSF distribution connects.
The board separates out the MSF signal into the clock's receiver
circuitry to provide the correct time setting, whilst the DC
power drives the mechansim. The end result being up to 100 slave
clocks all synchronised to a common time reference and powered
from a permanent supply — I said it was elegant!
Clocks can be supplied in a variety of styles and sizes (with
company logos printed on the face if required) from 90 mm designs
for installation within a console up to 400 mm faces for wall
mounting in a large studio. Digital LCD types are also available,
complete with day and date display modes if required.
Global Time
However, the cleverness of the system does not stop there. The
Master Clock controller — the source of the distributed MSF
timing signal — is the ARM3000 unit, a 1U rack mount box
with a handfull of buttons, a timing display and a back panel
full of connectors. The ARM3000 does not generate a 'wild' timing
reference, it derives its MSF signal from timing data transmitted
over the Global Positioning Satellites — GPS. A separate GPS
receiver head unit is typically installed on the exterior of the
building up to 100 metres away from the Master Controller.
The GPS timing data, and hence every connected studio clock, is
accurate to within 0.1 second anywhere in the world!
Consequently, TickTock systems installed in studios across the
county, continent, or around the world will be inherently and
accurately synchronised to each other.
The timing data embodied within the GPS signal is decoded by the
ARM3000 unit and then re-coded into an MSF format to drive the
connected radio clocks. The unit has provision to offset the GMT
time reference to take account of local time and can even
accommodate automatic Daylight Saving adjustments for summer and
winter time shifts. This resulting MSF signal is distributed to
two chains of cabled 'clocks' via a pair independently buffered
output ports. The unit also provides a number of other standard
and optional interfaces to pass radio timing data to a wide range
of external equipment. For example, there are six independent
changeover switch circuits (GPIs) which can be programmed to
operate at specific times.
An AES-EBU digital audio output option provides four 48kHz feeds
referenced from the GPS master clock, each carrying silence
('digital black') for synchronising digital studio equipment.
There is also provision for an optional RS485 serial computer
interface which is intended to send a timing update signal to
synchronise the internal clocks of networked computer systems,
such as audio editors, central servers and automated playout
systems.
For 'mission-critical' installations there is a full battery
back-up system and a second redundant controller with automatic
switchover can even be added. For audio broadcast applications
Audix also offer an integral PIPS generator option to produce
analogue and digital format audible time signals — the
number and duration of pips is user-programmable.
Conclusion
I find it comforting that despite the profusion of budget
equipment in broadcasting, often restricting the flexibility and
professionalism of the job at hand, sophisticated and
well-designed equipment like this is available to address the
needs of the modern broadcast installation in a very
cost-effective way.
Line Up - June/July 2000
ATM Audio Networking Solution
Audix Broadcast demonstrated their new industry standard ATM switched network interface at various exhibitions in 2000. Existing ATM services conforming to established world-wide standards can now be employed for highly scaleable, real- time audio networking applications. Using the new interface, high quality audio data can be routed reliably across an ATM network with complete compatibility with other independent data simultaneously sharing the service.
Developed in conjunction with a specialist data networking company, this new ATM audio interface is intended for installation in ADD Series digital broadcast consoles as a fully integrated element of the complete system. The associated controlling software not only manages the automated routing of full quality audio signals across the switched ATM network, but also supports related non-audio data streams, such as remote machine control commands.
Audix Broadcast Announce the ANTS Control System
Audix Broadcast are pleased to announce the launch of their new computer control system ANTS designed to provide an integrating link between their ADD Series of digital audio consoles, ATM distribution products, and a range of external source equipment. The ANTS computer interface system, combined with the powerful ADD and ATM technologies, provides greater integration and flexibility than any other similar system currently available.
The first implementation of this new ANTS system has been in a Bureau installation for a National Broadcaster to control their studio phone-in system. Providing a fully integrated control solution for all call handling and routing, the ANTS has easy to use facilities for call rotation and selection, automatic allocation to hybrids, and presenter talkbacks.
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