A Guide To Desktop Video Connectivity Solutions
Once upon a time it was easy to understand audio and video connectivity. Consumer products used an RCA connector (one for composite, three for component, and we won’t mention S-Video) and commercial products used BNC connectors (one for composite, five for RGBHV and we won’t mention S-Video). That pretty much summed it up for decades. That is with one glaring exception. The computer. Both laptop and desktop computers needed something a bit more compact and with some advanced capabilities, such as the ability to exchange EDID information with the display. A different connector was needed.
The VGA connector (Video Graphics Array) was first introduced with the IBM PS/2 line of computers in 1987. VGA also refers to a specific resolution, but for the purposes of our discussion we are focusing on the cables and connections. The VGA connector uses a three-row, 15-pin DE-15 that carries analog component RGBHV (red, green, blue, horizontal sync, vertical sync) video signals, and VESA Display Data Channel (VESA DDC) data. For nearly three decades this blocky analog connection ruled the office. It wasn’t particularly elegant, but it worked and was well understood.
Low-Voltage Differential Signaling (LVDS) is a physical layer specification that describes the way signals move between inputs and outputs on IC chips. In use since 1994, LVDS was used for computer video and graphics data transfers and drove the most advanced versions of VGA interface. LVDS became an increasingly important technology as computer resolutions began to escalate beyond 800 x 600 (SVGA), but the proliferation of digital video at the consumer level changed that. In part, digital video came with an unanticipated challenge. Digital rights management for content is a particularly thorny issue in the digital world. Unlike analog, there is no generational loss of quality when copies are made. In the digital world there are no copies – there are only clones!
Often erroneously referred to as “high definition copyright protection,” High Bandwidth Digital Content Protection (HDCP) is a system developed by Intel Corporation. HDCP leverages a key exchange protocol known as Blom’s Scheme. It’s intended to prevent encrypted content from being played on unauthorized devices or devices which have been modified to copy HDCP content. Before sending data, a transmitting device checks that the receiver is authorized to receive it. If so, the transmitter encrypts the data to prevent eavesdropping as it flows to the receiver. As computers and personal digital portables became a bigger and bigger part of our industry, and our lives, the demand for these devices to interface with just about everything became a driving factor.
On December 8, 2010 a joint press release from AMD, Dell, Intel Corporation, Lenovo, Samsung Electronics LCD Business and LG Display announced “intentions to accelerate adoption of scalable and lower power digital interfaces such as DisplayPort and High-Definition Multimedia Interface® (HDMI) into the PC” as an alternative to the aging, analog VGA connector. The press release went on to say that “Intel plans to end support of LVDS in 2013 and VGA in 2015 in its PC client processors and chipsets.” The death notice for the VGA connector had been posted.