The FPGA advantage
Oct 1, 2007 12:00 PM, BY TINO FIBAEK AND MARTIN S. WON
Fairlight’s use of an Altera PCI card enables design fl exibility, reduced cost and high performance.
Professional media equipment designers have traditionally relied on digital signal processing (DSP) devices to provide processing power for audio and video subsystems. As these types of equipment grow more sophisticated to align with consumer expectations, designers are finding that costs and complexity are also increasing.
DSP devices are a general-purpose, fixed-architecture technology covering many applications. As a result, conventional audio and video subsystems must rely on multiple and costly acceleration boards, each containing multiple DSP devices. Not only is this an inefficient use of valuable resources, it also results in a longer development cycle and a system that consumes more power.
Less is better
For better audio and video streaming performance at lower costs, Fairlight of Australia developed a media technology platform using a single Altera Stratix II GX FPGA-based PCI card rather than dozens of DSP devices. Tapping into the reprogrammability inherent in FPGAs essentially creates a universal hardware platform useful for a number of media applications requiring real-time audio and video processing power, from low-cost recording and editing platforms to large-format consoles with integrated HD video.
Industry studies show that an average DSP algorithm running on a low-cost FPGA provides up to 10-times better performance than it would if running on a low-cost DSP device. Costwise, FPGAs can generate from 10-times to 100-times improvement over DSP devices or microprocessors.
High-quality picture and sound
Fairlight's Crystal Core architecture, which uses a crystalline interconnect scheme at every level, is implemented in one or more PCI Express cards (called CC-1) connected to a host computer. The FPGAs in the system replace an eight-board, 64 floating-point DSP device-based design. (See Figures 1 and 2.)
Figure 1. Altera’s Stratix CC-1 board is 4in x 8in and replaces eight QDC boards.
The smallest configuration on a single CC-l card delivers 240 channels into an 80 bus mixer. Each channel is equipped with eight bands of EQ and three stages of dynamics. A midsize system — providing an increase of 960 channels into 320 busses — is created in a host computer with four CC-1 boards. Larger systems may be assembled using multiple hosts with no limit to the number of linked processors.
With the CC-1 card, media equipment designers have a means to create the larger, high-performance A/V systems consumers are demanding, while also meeting their budget requirements. A system used for sound design can be reprogrammed for HD color grading and, later, for music recording. FPGAs bring hardware-coded DSP functions including real-time processing power, finite impulse response (FIR) filtering, and fast Fourier transform (FFT) processing.
The flexibility of FPGAs means that many functions can be placed on the most efficient location in the logic flow of the device, rather than in peripheral hardware. For a design engineer, the result is a smaller and faster system that generates less heat. Also, the design process is simplified and less costly to undertake.
Figure 2. The Fairlight QDC board measures 10in x 10in. Altera’s Stratix CC-1 replaces these eight boards.
For audio processing applications, this media platform supports more than 200 channels of recording, editing, mixing, I/O and plug-ins. Latency is low, and full processing is available on each channel. Audio engineers can achieve better audio quality at a lower cost by choosing the appropriate level of processing for each system task, using a feature called dynamic resolution optimization (DRO). DRO takes advantage of the capability of an FPGA to simultaneously run multiple processes at different bit depths. DSP devices, in contrast, operate at fixed bit widths, performing all processes at a single resolution.
From a practical standpoint, using DRO means that equalization processing can be performed at 72-bit floating-point precision, mixing can be performed at 36-bit floating-point precision, and metering functions can be performed at 16-bit fixed-point resolution. For video processing applications, a single chip can play back and color-grade a full-uncompressed HD stream.
New opportunities for media equipment designers
Exploiting the flexibility and processing capacity of FPGAs, professional media equipment designers are gaining a cost-effective, power-saving alternative to traditional DSP device-only architectures. With this FPGA-based media technology platform, equipment designers have a reusable foundation for a variety of audio and video processing systems. Instead of resorting to multiple DSP devices, they can achieve better performance, lower costs, a smaller footprint and lower power impact with a platform based on a single FPGA hardware coded with DSP functions.
Tino Fibaek is the chief technology officer for Fairlight. Martin S. Won is a senior member of the technical staff for Altera.
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