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44 l March 2012


Comrex’s ACESS 2USB features two USB ports and support for select 4G Wireless cellular data service modems

COMPRESSION is something of a necessary evil. In some areas of broadcast operations there has been a move away from compressed audio – the transport of surround and multichannel audio is the leading example – but in others it remains the cornerstone. This is particularly true

of codecs for both reporting/contributions and transmission/delivery. With the first coming of ISDN in the early 1990s, there was resistance to this new way of doing things, with concerns over audio quality and time delays. But as coding technologies improved codecs and their algorithms expanded from being solely for exchanging short-form material, such as radio reports and ADR

of existing low bit rate services and carry more audio channels at a given bit rate. “We’re trying to develop codecs for every application,” comments Fraunhofer IIS spokesman Matthias Rose. “For the future, bandwidth will continue to be a valuable commodity, which is why low bit rate codecs are being developed. As broadcasters want to add more video, there is a good argument to use dedicated audio technology, which is why HE-AAC is so dominant.” McClintock sees the

development of technologies like Extended HE-AAA as part of “the march towards the Holy Grail of scaleable codecs”. CSR is also moving towards this goal; the first step towards aptX

“Most of the major radio broadcasters around the world have embraced IP codec technology because it provides complete mobility "

Chris Crump, Comrex

- how low can they go


sessions, into programme distribution to transmitters. Jon McClintock, director of sales and marketing for aptX, the audio algorithm development division of CSR, says that compression “needs better PR”. He agrees the word has gained negative connotations, which is why he prefers to use “bit rate reduction” and “non-destructive coding techniques”. However it is described, the

The codec is a key part of any equipment list but it continues to stir up technological controversy. Kevin Hilton looks at the ubiquitous box and the tricky issues of low bit rates and IP


ever-growing demands to get more data and channels on carriers in a limited bandwidth has increased the pressure on codec and algorithm developers to come up with systems that deliver good audio quality at lower and lower bit rates. German research centre

Fraunhofer IIS has been at the forefront of this with the AAC (Advanced Audio Coding) family of coding techniques. At Mobile World Congress 2012 in Barcelona last month, Fraunhofer announced a new variation of the HE-AAC (High Efficiency Advanced Audio Coding) format that takes the process even further. Extended HE-AAC has been designed to handle speech and music; it is claimed to improve audio quality at bit rates in the region of 8kb/s, with the capability to improve the quality

Scalable is the aptX Lossless algorithm, designed for applications such as WiFi where data rates are not as limited. McClintock envisages the

scalable codec as a device with “five or six metrics” for the algorithm, allowing users to select what is best for them. “I don’t think there will be a basement figure in terms of the bit rate,” he says. “It will probably keep evolving in stages. But the real challenge is not about bit rates, it’s power consumption and having an appropriate processor to run the algorithm.”

MAINTAINING QUALITY Peter Lee, vice president of European operations for Orban, sees a time in the future when transmission codecs will be working with narrower bandwidths even more than they are today. “The big question is whether all that will be good enough for broadcasters,” he says. “That depends on where the quality barrier lies. It is coming down. We have to be careful not to compress too much.” Kirk Harnack, product

manager at Telos, observes that the minimal bandwidth capability of HE-AAC and other new codecs “is useful for contribution audio from locations where connectivity is

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