Implementing Multi-standard Broadcast

Products addressing the global broadcast market must be both versatile and efficient if they are to meet the plethora of continuously evolving standards. Jim Whittaker, General Manager of Imagination Technologies’ Metagence Division, describes the market and technical challenges that are driving innovation in this increasingly digital domain.

The global digital radio, television and audio markets are experiencing considerable and rapid growth. In the UK, the digital audio broadcast (DAB) market in FY2004/05 is already expected to exceed 1.3 million units (with projected growth to 8.0 million units by 2008). Digital audio technologies require support for demodulation (COFDM), audio decode (MPEG-2, MP3, AAC, WMA) along with system control, full-featured user interface and audio playback. Integration with other applications, including automotive and mobile devices (phone, PDA and TV), is an emerging requirement.

A Burgeoning Market
The smart / feature phone, and entertainment market segments are also experiencing strong user uptake. Consumer products, providing advanced content for gaming, radio, personalized digital audio, mobile TV and communications, will be well-established by 2008. To enable this, mobile device technologies will acquire support for 3D graphics, video decode, image processing, audio decode and demodulation.

A true analog-to-digital conversion is already progressing in the digital TV market, where there is demand for low cost set-top boxes (STB) and digital-ready TVs (iDTV). Digital TV is well established in Europe: analog transmissions have already ceased in parts of Germany. By 2008 the projected worldwide market for LCD TVs is anticipated to be 60 million units. Market growth has been driven by the adoption of the MPEG-2 standard and the European Digital Video Broadcast project, while in North America and Japan, the ATSC and ARIB standards (based on MPEG-2) are now clearly defined. Although U.S. adoption is currently slower than Europe and Japan, broadcasters in both regions are committed to undertaking the digital transition. Within mobile TV, new standards are emerging — in the Far East, ISDB-Tss, T-DMB and CDM, and DVB-H in the European Union and the U.S.

TV technologies require demodulation (COFDM, QPSK and QAM) alongside support for legacy analog TV, video decode (MPEG-2, MPEG-4, H.264, WMV9), audio decode (MPEG-2) and system controls and user interfaces.

Broadcast Tech Figure 1
Figure 1: The Need for Multi-Standard Receivers

Opportunity vs. Challenge
Keen to exploit the rapid growth of their markets, manufacturers in the audio, television and global digital radio arena are focused on producing smaller and more flexible product ranges. These devices are designed to meet multiple standards, so that they are operable (and marketable) across multiple territories, thus removing the need to create individual builds for specific markets.

This challenge for manufacturers is made complex in the face of evolving standards and the demands for high quality transmission over the minimum bandwidth. To overcome application constraints, manufacturers must strike a balance between pure software-driven implementations and micro-programmable, fully hard-coded hardware solutions that enable product performance.

Across the broadcast market, digital video and audio applications actually share many requirements and technologies. Manufacturers can use common IP to customise and differentiate their product offerings, primarily through software.

To remain competitive, successful multi-standard broadcast IP technologies must deliver a variety of commercial advantages. As well as being flexible, off-the-shelf and re-usable (in order to enable low-cost solutions), they must also be SoC ready, offer innate high performance and provide advanced differentiation features. They also need to deliver universal communications management, providing a single chip that enables software-driven revisions and changes to make products for specific markets, territories and standards.

Solving Today's Architectural Challenges
The traditional approach to implementing such systems is to combine DSP, microprocessor and graphics acceleration cores in a multi-core configuration. Each specialist core is usually focused on one specific task. However, multi-core systems can be highly inefficient; 'hardwired' processors are inflexible, power-hungry and costly, so the use of multiple processors may represent an unnecessary replication of resource.

The approach Imagination Technologies has taken to address the real-time execution issues associated with the use of multiple processors within multi-core configurations is to use a multi-threading architecture. The META base architecture enables support for multiple hardware programming contexts. A unified, scalable processor core, with support for both DSP and general purpose instruction sets, can also perform cycle-by-cycle hardware scheduling and resource management, delivering a real-time response that meets today's market and product needs.

Broadcast Tech Figure 2
Figure 2: META Base Architecture

Global digital TV requires a configurable and programmable IP core, targeting the PHY layer of data communications standards; a programmable processor, coupled to high bandwidth memory, delivers performance processing specific to each standard. While architecture is finely tuned to specific application needs, this approach provides excellent silicon area and power efficiency. As well as providing dedicated hardware to support processing common to most standards, a programmable processor offers the configuration capability for a wide range of systems. It also provides a platform to provide SoftRadio and SoftTV implementations — enabling manufacturers to support legacy standards — providing performance enhancement via software upgrades.

An example of such a versatile IP core is available from Imagination Technologies. The Ensigma Universal Communications Coprocessor (UCC) which is a programmable signal processing unit designed to handle a range of worldwide TV and radio broadcast standards. The UCC is implemented as three processing units: the Signal Conditioning Processor (SCP), Modulation and Coding Processor (MCP) and Error Correction Processor (ECP). Each processing unit has its own dedicated signal tasks.

When not used for demodulating digital signals, the UCC can be reconfigured as a high quality adaptive digital 2D/3D Y/C separator and chroma decoder with ghost cancellation. This enables digital products to support legacy analog standards through software.

Design Constraints
Broadcast IP design is limited by constraints in terms of power-performance versus silicon area and cost. Encoding demands the highest performance requirements and design specialization, while decode is less intensive and highly standardized. Video processing tends not to use conventional DSP operations, requiring customization of algorithms to enable efficient implementation. It is an area that Imagination Technologies has researched extensively, resulting in the development of proprietary algorithms for many applications.

Video encode and image enhancement share similar operations (e.g. motion estimation). Programmable yet efficient architectures can be devised by taking advantage of common operations such as these.

Image enhancement is an area that has become important for digital video in enabling differentiation. Image enhancement through post processing can make a significant difference to the perceived quality of the viewed image; this enables manufacturers to differentiate consumer brands for say flat-panel TVs. Fundamentally, the quality of physical components that comprise a flat-screen TV is difficult to differentiate, however the application of image refinement through signal processing techniques can make an appreciable difference to the viewed image.

Low power is still an issue, despite many of these consumer applications being ‘tethered’ (i.e. there is no portable battery requirement). Low power enables low cost packages, and for consumer equipment, the requirement for active fan cooling is an important factor – from both a cost and a noise perspective. Consequently it is still necessary to make design ‘power-aware’, and many of the techniques employed are applied to the design of mobile devices.

Design Flow
Verification is always an issue when large quantities of data must be simulated in order to evaluate the algorithm, and this is the case with video where many frames of data must be processed. Emulation using FPGA boards can help in enabling the efficient assessment of subjective video processing algorithms.

Although developing broadcast IP follows a fairly standard SoC development route, the process is not a straightforward one. First, these are reasonably high-end chips, and anyone who has worked on a multi-million gate chip knows that achieving power optimization and timing closure can be a major engineering effort.

Design Flow Developments
As far as design flow is concerned, the unrelenting shift to smaller geometries poses new challenges which have to be overcome. Moving to a 0.13-micron silicon process required robust cross-talk and noise sign-off - a big issue that hasn’t been a requirement with previous process nodes. The design team here are now readying the design flow for 90nm processes. This includes looking at on-chip variation compensation for these advanced technologies.

Constantly improving accuracy of the design flow sign-off is essential if the chip is to operate at the desired geometry, and the performance potential of the process is to be fully realized. Quite a few companies have already moved to 90nm and some have openly said this has not led to any performance benefit. Yield can be a foundry issue or it can be that the sign-off flow is not taking into account the effects that it should be. The sign-off flow is critical in determining the performance and yield from the process.

Within Imagination Technologies, Synopsys tools are the current standard for final sign-off. These are well supported by the foundries we work with, and give excellent correlation between simulation and analysis and measurements from silicon. A major issue for sign off is that the data sets for deep submicron devices can be extremely large, so performance has to be good.

Future Applications
The broadcast market continues to evolve, with new cross-over products emerging. Areas in audio are now becoming prevalent in broadcast, for example in Korea, T-DMB (a DAB variant) is being used to provide both audio and video.

In the mobile area, DVB-H, ISDB-Tss and CDM are driving mobile TV products. HDTV, still in the early stages of rollout and take-up, continues to remain significant. As the digital market continues to grow, manufacturers will be obliged to provide software support for analog TV and radio in their digital solutions. To confront these multi-layered market demands, manufacturers need the flexibility and scalability to deliver multi-standard support on a common configurable hardware. In addition, products need to be easily upgraded to support new standards as they emerge.

Imagination Technologies develops and licenses innovative silicon and software intellectual property (IP) for system-on-chip (SoC) devices targeting multimedia and communication applications. The company offers an expanding range of complementary IP cores, licensed by many of the world's leading silicon device suppliers including Intel, Renesas, Samsung, Sharp and TI.

Current target applications include:
  • Mobile phone/PDA (graphics and video)
  • Digital video (TV, set-top-box, DVD)
  • Digital radio and audio
  • Car navigation/information
  • Amusement (arcade and slot-machine) devices

Licensing partners can tailor their SoC designs by combining one or more of these cores with supporting IP enabling rapid time to market and reduced development costs.

Imagination Technologies is organised into four highly complementary divisions. PowerVR, Metagence and Ensigma focus on IP generation and each develops a fundamental technology family for graphics/video, RISC/DSP processing, and broadcast and consumer communications respectively. PURE Digital creates award-winning consumer products which promote these technologies and pathfinds new market areas. The company employs over 270 people, including over 200 engineers, plus business development teams to market products and support partners.

Following a Cambridge EIST course, Jim Whittaker worked at Inmos (now ST Microelectronics) for 3 yrs before joining Imagination Technologies.

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By Jim Whittaker
 -Imagination Technologies
"Within Imagination Technologies, Synopsys tools are the current standard for final sign-off."