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48 l March 2012


www.prosoundnewseurope.com


broadcastfeature


entertainment. Contribution use is a big factor, too. ISDN is still useful, where it is available. And there’s a huge deployed base of ISDN codecs. Existing ISDN codec installations will continue for some years, but prospects for new ISDN deployment by the phone companies get slimmer each year.”


McClintock sees the


“wholesale migration” from synchronous networks to IP as “the single biggest change” in the codec sector. “To a certain extent the aptX algorithms struggled in the synchronous era when competing against the various perceptual-based coding algorithms, like MPEG2, MP3


CODING TECHNOLOGIES –PART TWO APT


The APT algorithm appeared in the 1980s as part of Dr Stephen Smyth’s doctoral research. The aptX technology was launched as a semiconductor system with a DSP integrated circuit. It became a key part of codec development in the early 1980s,


forming the software basis for a range of APT hardware. These two sides are now separate companies, with apt-X part of CSR. The range includes: aptX Enhanced for hig- quality audio; aptX Live, aimed at digital wireless systems; aptX Bluetooth; and aptX Lossless for low bit rate operations.


` `


The Bridge IT 4P audio codec will be on Tieline’s stand at NAB


and AAC. The broadcast world was


willing to sacrifice both audio quality and latency for a reduction in operational expenditure. With the advent of Audio over IP, broadcasters had an opportunity to vastly increase their data capacity without significantly affecting their operating costs. However, Audio over IP by definition suffers from latency as it’s a packetized architecture and has a lack of clocking. As such, perceptual-based codecs and Audio over IP became almost a mutually exclusive combination for two reasons. Firstly the total accumulated latency could be 120+ milliseconds and secondly the latency was highly variable, which is why there has been a return to aptX. Not only was the bandwidth supportive of aptX but because of the underlying sample based nature of aptX and its natural low latency, broadcasters could get a complete delay of under 50ms.” Gustavo Robles, director of


international sales at AEQ, which produces the Eagle ISDN and Phoenix IP codecs, says the internet protocol has made inroads into the broadcast market but is yet to become as well established as professional broadcasting networks, due to telco problems. “In most projects we see IP appearing as ISDN+IP, or as an ‘IP-ready’ request in tenders,” he says. Robles’ comments show that


there is still doubt about whether IP is ready to be the sole carrier for both contribution and transmission audio.


Among the companies that


are not convinced is Glensound Electronics, which produces codecs for reporters and commentary installations. “We get asked every day about when we are going to produce an IP codec but other projects and the lack of robust, simple standards for IP have disillusioned us,” says marketing manager Marc Wilson. “Although IP has become the most popular codec option, we are still selling our ISDN commentary units. Where ISDN is available it is still the reliable and robust choice.” A company that took some time to produce an IP codec was SystemBase, which now has the


C510ip and C520ip among its offering. Managing director Andrew Steward says this delay was intentional, partly because he did not want to buy in IP stacks and so spent three to four years producing the company's own from scratch. “Now we've got the background we need,” he says. “Once you’ve got that you can look at the IP connections and see what’s going on. From this work it’s all about the error management and you’ve got to design around that because most of the data over IP is not going to get through.” An example of this is the


production communications on reality show I’m a Celebrity Get Me Out of Here, which is staged in Australia and used SystemBase IP Codecs. Steward says 10% of the data did not arrive at the broadcast centre in the UK but due to forward error correction technology the stream could be supported. “It works remarkably well,” he says, “although it’s not foolproof.”


AUDIO AND IT IP has taken the audio codec, a relatively new but still traditional piece of broadcast hardware, into the realms of IT but that does not necessarily mean it will be eventually replaced by software equivalents. “We feel 3G plus WiFi has a lot to offer the reporting sector,” says Robles, “We are still working on software codecs and iPhone app codecs but most of our customers demand professional broadcast quality with good security. For that, dedicated hardware audio codecs are still the best.” Harnack agrees: “Dedicated-


use boxes tend to work well and people like the reliability they offer. There were software ISDN codecs for your laptop, but how many laptops have an ISDN connection? IP codecs make more sense for general computer platforms but there will always be trade-offs with simplicity and reliability due to operating system complexities and other software competing for limited CPU and memory resources.” So even though there is still a


debate over carrier technologies and compression, don’t expect that box to disappear from the racks any time soon. www.aeq.eu www.comrex.com www.csr.com www.glensound.co.uk www.orban.com www.telos-systems.com www.tieline.com www.systembase.com


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