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Advanced DVD Players With MPEG-4 Part II - The Hardware Perspective
by Ken Lowe, VP business development and corporate communications, Sigma Designs, Inc.

This is the second of a three part series. Part I provided background on the DVD and where we might see this technology take us. The second part looks at the hardware and the third part takes an in depth look at the software designers' perspectives for an advanced DVD player.

In this second article of our three-part series discussing advanced DVD players, we focus on the design considerations and feature-cost trade-offs faced by the hardware designer. In the first article, we discussed the expanded role of DVD players driven by the proliferation of downloaded formats, especially MPEG-4, and the improvement of the visual experience. As these advanced DVD players head toward a generation of multi-function, multi-format, high definition, graphically-driven audio/video appliances, it creates an expanded set of parameters that both hardware designers and software programmers must deal with.

DVD Player Hardware Architecture

Today's typical DVD player is based on a highly integrated motherboard, an IDE drive assembly, front-panel control assembly, power supply, and the miscellaneous mechanical elements that comprise the enclosure, switches, etc. As the basic DVD player now represents a commodity, there are only two primary segments: economy-where the designer's challenge is achieving standard features for the lowest cost; and premium-where the designer's challenge is achieving the richest mix of features at a reasonable cost. For the purposes of this article, we will focus on developing a motherboard for the latter segment along with its relevant trends and issues.

Figure 1 shows a block diagram for the motherboard in today's typical DVD player. As is evident, the design has been reduced to a highly-integrated single-chip DVD decoder chip, video memory, Flash program memory and a small set of minor components. Most DVD decoder chips today contain all the circuitry required to interface directly to the subsystems, perform decoding, and output the video and audio signals. In most cases, these decoder chips use SDRAM for video memory (typically 2 MB for a low-end player), and between 512k and 2MB of Flash program memory. Nearly all decoder chips incorporate a built-in TV encoder to directly output NTSC/PAL video in composite or S-video form, with many also supporting component (YPrPb) output. Most decoder chips directly support the S/PDIF format for Coax or Optical digital audio output, but require external audio DACs and amplifiers to achieve high-quality sound for the analog audio outputs. Direct interfaces also exist to connect to the DVD drive, via an IDE interface (or in some cases, a simpler DVD loader), and the front panel interface.

Figure 1: DVD Block Diagram
Click for entire image (19 KB)

Supporting New Standards And Formats

Though there are several categories of advanced features for DVD players, the ability to support the widest range of standards and formats quickly reaches the top of the list. This encompasses not just the published DVD and CD media standards, but the audio, video and still image formats that are becoming prevalent on the Internet. Table 1 contains a listing of the most popular of these formats along with a comparison of their support by popular DVD chipset manufacturers. Ironically, the support of any of these media formats does not bear any direct cost for the motherboard, excepting any minor premiums charged by the chipset provider.

TABLE 1: Supported Media Formats by DVD Decoder Chip

This table evidences the trends in advanced format support, as the most recent of these chips generally supports the widest range of standards. Obviously, all DVD decoder chips must provide fully compliant support for DVD-Video, CD Audio, and VideoCD (VCD) decoding.

Beginning in the 2001 Christmas selling season, the majority of DVD players also started supporting MP3 playback. DVD-Audio has had a rough time establishing momentum over the past year, but is seen as a prevalent standard for many new player models for 2003. Still image viewing, primarily using the JPEG format, is driven by the age of digital cameras and Internet/e-mail exchanges and should become quite common, especially through the promotion of Kodak's and other PictureCD formats. WMA (Windows Media Audio), which provides access to an increasing range of published content, is set to become pervasive and is supported by two of the devices listed above. Finally, MPEG-4 video content is rapidly gaining widespread use, either downloaded or user created from publicly available CODECs by Apple, DivXNetworks or Sigma Designs. Though there are other trade-offs to consider, the safest route is always to support of the widest range of standards, especially since their proliferation on the Internet can create a rapidly changing landscape.

Advanced Video Output and Other Features

Next on the list of advanced features are the set of video quality enhancements, some of which require the use of a recent model digital-ready television set. To begin with, all DVD players must provide a quality TV encoder to support direct NTSC/PAL output, which adds no extra motherboard cost. Progressive video output, once a feature only supported by high-end DVD players is now also a check-off item for most recent model DVD decoder chips. On the other hand, adding high definition video output is a different story.

High-definition video provides an exceptional viewing experience on televisions that support it, especially for still images. This starts with a higher performance video output stage in the decoder chip to handle 720 progressive (720p) and 1080 interlaced (1080i) formats with either component analog or DVI digital output. Scaling to high-definition video output also requires additional memory bandwidth, as well as a higher speed video pipeline. To achieve these resolutions, the video circuit and video DACs will be running at 74MHz clock for 1080i output, compared with typical 27MHz for PAL/NTSC.

From a motherboard standpoint, this means increased design considerations and tolerances in the video output stages as well as added connectors on the back panel. Though the increased resolution will expand video memory requirements, SDRAM memory is relatively inexpensive and is available in minimum sizes. Collectively, the increased memory, connectors and miscellaneous costs associated with adding high-definition support currently amounts to under three dollars in material costs. This cost is relatively minor in comparison to the $50 plus price premium that this type of player will retail for.

Another primary consideration is power dissipation, mostly attributed to the DVD decoder chip and its power management circuits. This is an area where a wide range of disparity can be seen amongst components. Some of the hottest and least expensive chips burn power in the range of 2 watts, whereas some of the latest chips operate near the 1-watt range.

The majority of new DVD decoder chips support many of the new media formats, progressive video and other enhancements. A recent example is the EM8500 from Sigma Designs, which supports, essentially all the formats covered and is the first to add MPEG-4 support to this list. This progressive DVD decoder also supports high-definition scaling, with direct component output and support for DVI output, adding an extra SDRAM memory chip to accommodate the expanded resolution and functionality. Designed to operate in a fan-less environment, the EM8500 is a fully power managed chip that dissipates approximately 1 watt of power.

As DVD players take on more advanced features their architecture, chipsets and cost continue to lead them into a path of convergence with other set-top appliances. Ultimately, consumer demand will decide what is the right price/performance trade-off and what form of convergence product provides the best utility.

Author's Biography

Ken Lowe is currently the vice president of business development and corporate communications for Sigma Designs, Inc. His role in this position includes developing strategic partner relationships, directing public and investor relations, directing trade show and special promotions and managing market research. Lowe holds a BSEE degree from California Polytechnic State University at San Luis Obispo, Calif.

Part I

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