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December 2012 l 29


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processing stages and convert between different digital formats while maintaining very low latency end-to-end through our processing engines.” Nonetheless, he admits that “it is difficult to envisage a time where [FPGA] becomes the right tool to perform the primary signal processing on professional mixing consoles”. Stadius also points to FPGA’s


inherent limitations. Standard chips, he says, will


continue to have their place in DiGiCo’s product range; FPGAs are “good for a huge number of repetitive tasks, but they are not very intelligent. We can embed microprocessor


our SHARC processors, better at the complex floating point calculations that are at the heart of much of today’s advanced signal processing”. Both now and in the future, he depicts a processing landscape in which FPGA and DSP “can coexist quite nicely” – particularly given that the functionality of the latter continues to expand. Analog Devices points to several recent developments in its own range, including the embedding of fixed-function hardware accelerators in some of its processors that “offload computationally intensive operations, allowing the core to


“DSP use has not gone away, and overall use for pro-audio products has actually steadily risen during [recent years]” Denis Labrecque, Analog Devices


cores in them, but when it comes down to controlling the whole system we still need powerful processors such as TigerSHARC DSPs and Intel PCs. Standard chip technology also covers areas such as A-D and D-A conversion, clocking, power supplies, etc. None of these can be handled by an FPGA.”


‘COEXIST QUITE NICELY’ An ocean away – in San Jose, to be exact – Denis Labrecque from semi-conductor and signal processing IC specialist Analog Devices is reflecting on the enduring nature of the FPGA vs DSP debate (“I have gotten this question for several years now”). But, he implies, there is no reason for it to be framed within a context of opposition: “While the use of FPGAs has certainly increased, especially in the higher-end equipment like large format mixing desks, DSP use has not gone away, and overall use for pro-audio products has actually steadily risen during this time.” FPGAs, he acknowledges,


“are very good at several things – massive I/O management and algorithmically simple operations, such as filters and FFTs, for example”. But dedicated DSPs, he maintains, “can still be more flexible, easier to program and, in the case of


focus on other tasks”. Further R&D has also brought “more specific audio-centric functions to our SHARC, Blackfin and SigmaDSP processors, including a large number of serial ports, flexible signal-routing units, multiple onboard sample-rate converters, internal codecs, etc”. Total development costs will also continue to play a decisive role, with Labrecque remarking that DSPs have “extensive, mature code development environments, large libraries and relatively large numbers of seasoned programmers. With software in many designs taking up a large [percentage] of design costs, these points should not be disregarded – even for mid-volume applications.”


Months – nay years – spent


investing in signal conditioning code should not be overlooked. “For many, it’s still more efficient from a time and processing perspective to run their existing DSP library on an established DSP architecture, as opposed to recreating this functionality in an FPGA environment,” he says. THAT Corporation also


continues to reap the rewards of non-FPGA-based products. In a digital era, “analogue is not growing, but for us it is because other guys have abandoned or neglected it,” remarks Les Tyler, president of the Massachusetts-based analogue IC specialist. He points to encouraging demand for three recent product releases – the 1583 Low Noise Differential Audio Preamplifier IC, the 4316 Very Low Voltage Low Power Analogue Engine and the 5173 Digitally Programmable Gain Controller IC – and confirms that the company remains set on a course of “trying to find more ways in which analogue tools – and relatively high voltage tools at that – can be applied to


THAT 4316 Very Low Voltage Low Power Analogue Engine


solve problems within pro- audio. Power distribution [is just one example].”


FULL CIRCLE? With the lay of the processing land fairly clear at present, it’s reasonable to wonder what the next ‘great leap forward’ might be. Predictably enough, lips generally remain sealed, with Stadius quipping that if “I told you what the next paradigm shift in terms of audio technology was I would be giving the game away and I would have to shoot you!” Moments later,


however, he backtracks slightly to offer a


tantalising glimpse into a


future in which old and new processing technologies might dovetail effectively. Recent developments mean


Fairlight’s Crystal-Core Engine implements FPGAs on a PCIe card


ANALOG DEVICES: CRYSTAL BALL TIME


“Predictions are difficult,” says Denis Labrecque, “and I’m constantly amazed at what our customers do with our products – sometimes using them in ways we never imagined. I think we will see more ‘intelligent’ devices based on deeper integration of multiple technologies. For example, speakers with a


gyroscope that tells the DSP to adjust the crossover and EQ based on if it is being used horizontal on the floor as a monitor or vertically mounted as an array. Also channel strips that ‘know’ what is plugged into them and pre-configure a signal chain with suggested inserts. This is already happening – both of these


features can be found in the new StageScape System from Line6, but it’s the tip of the iceberg. Another trend is ‘edge’ and ‘distributed’ processing; rather than having all of the signal conditioning in a central unit, the DSP is being located at the very back end of the audio chain (DSP in speakers) and now, in the front end of


devices, with DSP in microphones as well a myriad of pre-processing effects. Other trends that drive processor development include 3D/surround audio from fewer speakers, and the emergence of networked audio, both wired and wireless, with an industry drive towards Ethernet AVB connectivity.”


that it is now possible to shrink vacuum tube technology down to nanoscale size. “A vacuum is better than any semiconductor because the electrons can shoot through ballistically without getting scattered by the lattice of the silicon,” Stadius notes. “This


KEY POINTS


l FPGAs enable powerful parallel processing, particularly within large- format consoles


l Standard chip technology is still in demand for applications including overall system control, A-D, D-A conversion and clocking


l Next stop: nano tube FPGAs...


technology is real and perhaps soon there will be FPGAs based on this technology. So we have gone full circle, starting with tubes and ending with them... albeit on a nano scale.” It’s an appealing thought.


But while we wait, a future in which FPGA-based solutions and conventional DSP continue to dovetail neatly in order to achieve all necessary processing tasks effectively and cost-efficiently appears to be a certainty. n www.analog.com www.digico.biz www.fairlightau.com www.soundcraft.com www.thatcorp.com


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