Metric Halo Mobile I/O Unit Provides Professional Sound in Laptop Size, Thanks to SHARC®

Bands on tour, movie crews on location, and producers of large venue events need the flexibility and freedom to adapt to situations at hand, especially when it comes to recording. With each new location come unfamiliar control rooms, control panels, and sound systems that can sometimes require hours of setup. Not to mention the ever-changing face of technology, with new multi-format, multi-standard, media-rich devices coming out all the time. Whether analyzing a PA, mixing an album, or recording ready-to-use audio files on a movie set, sound engineers need familiar tools in a compact setup that can go anywhere.

Metric Halo, with its seven-year history of developing signal-processing solutions for the professional audio industry, knows what it takes to accommodate musicians on the road. In fact, the company's Mobile I/O line of FireWire interfaces, which gives sound engineers the power and sound of a professional recording studio in about the same dimensions as a laptop, has seen live tours with such cutting-edge bands as "No Doubt," "Dave Matthews Band," and John Mayer. Metric Halo products were also used in films such as Mel Gibson's "The Passion of the Christ," and international events such as the opening ceremonies of the 2004 Summer Olympics.

When Metric Halo was looking for a processor to drive Mobile I/O, designers wanted one that was cost-effective, superb at floating-point operations, and versatile enough to handle communications, system control, and audio processing. Metric Halo chose a SHARC processor from Analog Devices, Inc. (ADI). "SHARC was by far, the best solution for us," said Dr. B.J. Buchalter, V.P of R&D at Metric Halo. "SHARC is flexible enough to support all of our requirements, and at a modest cost per part."

Test: One, Two
Metric Halo realized that sound engineers on the road are plagued with hours of sound checks, phasing problems, and ever changing venues and rental equipment. The company wanted to develop a portable, signal-processing interface that could turn a laptop into a miniature console. So the company set out to develop a modular pro audio processing unit sound engineers could take anywhere – Mobile I/O. The interface itself was to include FireWire connectivity, A/D and D/A converters, and powerful onboard processing to allow engineers to record, play and mix anywhere, anytime with top-notch studio quality.

Metric Halo found the majority of traditional digital signal processors on the market incapable of supporting portable media-rich audio applications flexibly and efficiently. They also didn't have sufficient system control capabilities for demanding signal-processing applications. Metric Halo found ADI's SHARC processor perfect for the job. The first implementation of Mobile I/O was based on a SHARC ADSP-21065L processor, a powerful member of the SHARC family of 32-bit processors optimized for cost-sensitive applications. SHARC (Super Harvard Architecture) offers the highest levels of performance and memory integration of any 32-bit processor in the industry targeted at audio applications. In addition to 32-bit fixed and floating-point data types, SHARC offers a unique, 40-bit floating-point data type, which is perfect for demanding audio applications. It combines a floating-point processor core with integrated, on-chip system features, including 544Kbit SRAM memory, a host processor interface, a Direct Memory Access (DMA) controller, a SDRAM controller, and two enhanced serial ports.

Making the Most of I/O
Buchalter says Metric Halo utilized virtually every I/O feature of the processor. The company implemented a solution that employs a cluster of two SHARC processors and a field programmable gate array (FPGA). Metric Halo implemented FireWire for Mobile I/O using the FPGA (which supports isochronous data) coupled with standard 1394 LLC and PHY silicon. FireWire (also known as the IEEE 1394 standard) was chosen because it is a high-speed serial bus that allows for the connection of up to 63 devices and supports hot swapping, multiple speeds on the same bus, and isochronous data transfer. It provides guaranteed bandwidth for multimedia operations.

Metric Halo used all of the serial ports and most of the flag pins of both SHARC processors. The synchronous serial ports on the ADSP-21065L SHARC provide an inexpensive interface to a wide variety of digital and mixed-signal peripheral devices, operating at 1x clock frequency. Serial port data can be automatically transferred to and from on-chip memory via DMA, without processor intervention. "Both SHARC processors fully utilize the chained DMA resources of the SHARC architecture," says Buchalter.

What's more, ADI's glueless cluster-bus technology, in combination with Metric Halo's own dynamic linker (which compiles and links signal processing plug-ins into the running code) allows Mobile I/O users to "patch in" to the signal flow running through the box. Users can construct complex signal processing chains out of more basic elements to further sculpt the sound of audio running through the interface. "Our Mobile I/O system also supports in-circuit re-programming," Buchalter explains. "Customers can update the FLASH, firmware, and FPGA micro-code via the FireWire-to-SDRAM interface. The process uses the full spectrum of the ADSP-21065L SHARC processor's I/O and memory features, seamlessly integrating arbitrary user code into a running system."

More Processing Power Please
Because the signal processing requirements of dedicated media processing systems grow exponentially, Metric Halo realized that the Mobile I/O product line would eventually need a much larger reservoir of processing power. To prepare for this, the company adopted ADI's third-generation ADSP-21262 SHARC processor. With its core running at 200MHz, the ADSP-21262 SHARC processor is capable of executing complex operations more than 2.6x faster than comparatively priced processors. In audio applications, its single-instruction, multiple data (SIMD) mode effectively doubles the processor performance.

For the next generation of its Mobile I/O product line, Metric Halo developed a hybrid design that incorporates the ADSP-21065L and ADSP-21262 SHARC processors. "We separated the FireWire and control stacks from the audio processing engine, to make both portions of the product more robust, flexible and powerful," said Buchalter. "We moved all of the audio processing onto the ADSP-21262 SHARC, because it supports them best." Since the FireWire and control stacks can't take advantage of the ADSP-21262 SHARC processor's SIMD extensions, Metric Halo dedicated the full power of the ADSP-21065L SHARC processor to FireWire processing. "The programming architecture and development tools are virtually the same for both processors, so we were able to move the existing code to the new processor easily with the exception of a few tweaks, which saved us a tremendous amount of time and money," said Buchalter. "And since the ADSP-21262 SHARC cluster is so much more powerful, we deployed more processing and more intensive algorithms." Metric Halo developed its own clustering for the new processor.

Metric Halo continues to broaden the I/O options available with its products, increasing the amount of digital signal processing power available on each board. Ultimately, this means buying more and faster processors. The company has also been working hard to publish an open-source software development kit (SDK) to allow third parties to develop their own signal processing plug-ins for Mobile I/O.

By taking advantage of the SHARC's high-performance signal-processing core, sophisticated memory and I/O subsystems, and flexible algorithm development environment, Metric Halo created a portfolio of pro audio products that bridges the gap between the studio and the road. Mobile I/O brings power, portability and sheer sound quality to recording/editing/mixing systems, interfacing a computer seamlessly with the audio world, both in the field and in the studio. If you're a musician, producer, or sound engineer who's dissatisfied with the sound you're getting for that on-location concert, movie, or event, don't worry. With portable solutions from ADI and Metric Halo, you can fix it in the mix.

For more information about Metric Halo's products, visit their Web site at Metric Halo.

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