Decoder with a switch

A new chip converts standard and high-definition video signals to a computer video format.


National Semiconductor

has introduced the industry’s 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 increases compatibility between different video standards and formats, allowing consumers to output video directly from DVD players, gaming devices and other devices to their personal computer monitors.

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

The LMH1251’s conversion process is done using analog technology via a colour-space conversion matrix, eliminating multiple stages of digital implementations.

It converts video to within 1% accuracy based on vector scope analysis, which exceeds the accuracy of current solutions on the market. 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 by 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 colour-space conversion and outputting the video in a RGBHV format.

The LMH1251 eliminates the need for a microcontroller to choose the proper detection scheme and also saves board space by integrating all the necessary components: a sync processor, a 2:1 MUX and an analog color-space conversion matrix.

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.