HDTV: If you haven't already bought one, you probably want to, and that's OK. That big-screen desire is nothing to be ashamed of. At least, that's what I'm telling myself.
While a mix of consumer demand and FCC-mandated migrations in television help build big volumes in high-definition television, the technology of choice for implementation remains a battlefield. As has been the case for some time, projection technologies of several stripes and flat panels such as plasma (and potentially LCD) are all competing to take a sizable-but ever-declining-chunk out of your wallet.
Some see HDTV and large-screen panels as the simple evolution of television; others view them as part of a broader home broadband media center play, where your PC is as involved in content as your cable provider. Both camps are probably correct, and as such, HDTV is quietly growing into the "next big thing."
To take a quick pass at one example of an HDTV implementation, we'll look at the Panasonic PT-50LCX63 50-inch digital LCD projection direct-view system. Loaded with picture-in-picture, split screen and an array of audio, video and memory card inputs, the Panasonic's digital image processing resembles that of a graphics computer. Along with the usual video inputs and outputs, however, mixed-signal engineering provides a critical link to get your favorite programming onto the big screen.
Starting with the inputs to the system, content can originate from satellite boxes, cable providers, S-Video, composite-video and VGA sources. Along with a standard tuner assembly, image inputs pass through an A/V switching fabric, an ATI NXT2003 DTV processor and other devices to support input formatting to a common protocol. The confluence of A/V signals ultimately ends up at a Panasonic MN2WS0010 HDTV LSI device, which handles all back-end processing for the digital A/V stream and-as testament to the high-end graphics bit crunching-is supported by Rambus memory.
More-direct HD feed is enabled by a chip from Silicon Image (the SiI9993), which accepts high-definition multimedia interface (HDMI) input, an uncompressed, all-digital audio/video interface standard. The PT-50LCX63 can also be used for playback of digital photos via a TV front-panel memory card slot, where an ESS device (the ES6420F) serves as the interface between the Secure Digital card and system electronics.
Moving closer to the display side of things, an iChips IP00C720 image-scaling device is used, presumably for resizing of input signals to a revised target resolution and aspect ratio. Xilinx supplies two configurable-logic-block logic arrays (Spartan XC2S50E) for driving a National Semiconductor low-voltage differential-signaling (LVDS) driver (the DS90C385MTD) and formatting input HDMI signals respectively.
The LVDS driver represents the point at which signals are ready to be sent to the assembly supporting the three high-resolution LCD panels-one for each of the primary colors (red, green and blue)-which generate images for projection. As one can imagine, supplying enough information to refresh the high-resolution picture around 30 times per second while accommodating 16.7 million colors means a whole lot of data. Specifically, the LVDS link supports a blazing 1.4 Gbits/second, and while LVDS is a digital transmission, significant mixed-signal finesse is needed to reliably transmit the high-speed bit stream, in essence a wideband analog signal-integrity challenge.
Once data arrives on the LCD board, a National Semiconductor LVDS receiver (DS90CF386NTD) re-creates a 24-bit parallel data stream for delivery to a Kawasaki ASIC. The Kawasaki chip (E07050K0B) shuttles data to a set of Analog Devices
10-bit high-voltage digital-to-analog converters (AD8383), which directly interface to the LCD panels. With such a huge color palette, delicate and precise control of the analog signal levels driving the LCDs is critical to keep hues, brightness and uniformity all up to spec.
To get to the final step and go from driven LCD panels to on-screen images, a high-intensity lamp is collimated, split and spectrally filtered to pass through each of the LCDs, which act as light valves for modulating the primary-color images. A series of complex prisms and lenses recombines the output of the LCD panels and projects them via a reflecting mirror onto the large front-screen panel, itself a trick piece of optics engineering.
A mix of other memories and microcontrollers surrounds key image-processing pieces, and total electronics complexity is quite high. Yet the total cost contributions of electronics are outstripped almost 2:1 by the substantial optics, LCD panels and enclosures.
At $2,500 to $3,000, the Panasonic isn't cheap. But it is still less expensive than the plasma and LCD alternatives on a cost-per-diagonal-inch basis. Whether other viewing or thinness qualities of true flat-panel displays win the day is an open question, but it seems likely that all the HDTV alternatives will find their own market segment success.
Like me, many of you are probably pondering the cost/performance trade-offs for your own upgrade in televisions. Of course the longer we hold out, the better the deals are sure to become.
David Carey, president of Portelligent. The Austin, Texas, company produces teardown reports and related industry research on wireless, mobile and personal electronics (www.teardown.com).
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