Decoder boosts compatibility between video formats

Santa Clara, Calif. — National Semiconductor Corp.'s video decoder is said to increase compatibility between different video standards — allowing consumers to output video directly from DVD players, gaming devices and other devices to their PC monitors.

National claims this is the first decoder with an integrated 2:1 multiplexing (MUX) video switch that uses analog technology to accurately convert standard and high-definition video (YPbPr) signals to a computer video (RGB) format.

The LMH1251 also performs all the necessary sync processing to generate horizontal and vertical sync signals from standard (SD) and high-definition (HD) video formats.

National's LMH1251 converts video to within 1 percent accuracy based on vector scope analysis. The device accepts one set of YPbPr inputs and one set of RGB/HSync/VSync inputs. Using the integrated 2:1 MUX and based on the input selected, the output will be either a decoded TV or buffered PC video signal. The LMH1251's RGB path has 400 MHz of bandwidth, enabling it to accept up to 1600 x 1200 UXGA video resolutions. The output displays the unaltered RGB video signal.

The YPbPr video path has 70 MHz of bandwidth. It is equipped with a smart video detection circuit that automatically senses 480i, 480p, 720p, 1080i and 1080p video formats, applying the appropriate color-space conversion and outputting the video in a RGBHV format. The LMH1251 eliminates the need for a microcontroller to choose the proper detection scheme.

“Converting signals in the analog domain through National’s integrated, all-in-one decoder gets rid of all the complex external circuitry or additional chips you'd find in a digital solution,” said Erroll Dietz, vice president of National Semiconductor’s amplifier products group.

The LMH1251's conversion process is done using analog technology via a color-space conversion matrix, eliminating the multiple stages of digital implementations. The result is a cleaner, crisper decoded video image that is superior to alternative approaches that use discrete components, digital products or field-programmable gate arrays (FPGAs), according to Dietz.

See related block diagram

Available now in a TSSOP-24 package, the LMH1251 is priced at $3.49 in 1,000-unit quantities. Lead-free package options are also available. Click here for the LMH1251 data sheet.

National Semiconductor , 1-800-272-9959,

The real beauty of this video decoder, which is the first product in this upcoming family of video products, is that you can turn your ordinary CRT or LCD computer screen into a HD video display without external components or software, without a TV, HDLCD panel, or an expensive video processor.

The flat-panel monitor market is segmented into three categories: the basic monitor, a multimedia monitor and the very high-end multifunctional monitors. Basic monitors have only RGB inputs, while multimedia monitors support RGB and digital video interface (DVI), as well as integrate speakers. The multifunctional monitors have fully integrated digital video processors supporting S-video, component video, DVI and RGB, tuners and integrated speakers — but many consumers are unwilling to pay the high price for these high-end monitors, said Robert Eddy, director of marketing for National Semiconductor's amplifier group

The LMH1251 will enable monitor manufacturers to create a new segment in the market — the HD ready monitor at a price point between multimedia and multifunctional monitors, Eddy said. This new HD-ready monitor segment will enable a second high-definition video display in consumer's homes for Sony PlayStationII, Microsoft Xbox, HD set-top boxes and progressive scan DVD players. “The LMH1251 enables monitor manufacturers to offer products that will support UXGA (1600 x 1200) RBG resolutions and standard component video 480i through 1080p inputs,” Eddy said.

If a consumer wants to display video on a basic monitor or multimedia monitor, converter boxes are available on the market that do the same thing as this video decoder but they require 30 to 40 discrete components and sell for about $100, Eddy said.

Other unique aspect of this part, which is difficult to achieve with discrete solutions, is the color decoding and sync processing. “Our product automatically detects if the video source is 480i, 480p, 720p, 1080i or 1080p and converts the color from component video to RGB. The user does nothing,” Eddy said. In component video, the horizontal/vertical sync signals are embedded in the luminance (Y) portion of the video — so this device also does the sync processing. “It strips the horizontal/vertical syncs off of the luminance (Y) signal and separates the horizontal/vertical sync signals,” Eddy said.

Presently, color-space conversion is done in the digital domain of high-end digital video processors and scalars such as National's AVC2510 and AVC5000. These high-end products are targeted for the HDLCD TV market and have too much functionality to meet the price points of today's monitors, Eddy said.

Analog technology sets this color decoder apart from the rest of the digital solutions out there. The LMH1251's color space conversion in the analog domain enables higher resolution and better signal to noise performance, Eddy said.

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