Glossary

Video Matrix

A Matrix Switch is a switch connecting multiple inputs to multiple outputs in a matrix manner. Originally the term was used literally, for a matrix switch controlled by a grid of crossing metal bars, and later was broadened to matrix switches in general. It's one of the principal switch architectures, together with a memory switch and a crossover switch.

Video Router

Inputs and Outputs
The number of inputs and outputs varies dramatically. The way routers are described is normally number of inputs by number of outputs e.g. 2x1, 256x256.
Signals
The type of signals transported can be anything from analogue composite video signals PAL, NTSC. Analogue components, Digital: SDI, HD-SDI. Also Broadband routers can route more than one signal type of Digital video eg SDI and HD-SDI.
Crosspoints
Because any of the inputs can be routed to any output, the internal arrangement of the router is arranged as a number of crosspoints which can be activated to pass the corresponding signal to the desired output.
Control Panels
Many type of control panels can be use to control the video router.

VGA

The term Video Graphics Array (VGA) refers specifically to the display hardware first introduced with the IBM PS/2 line of computers in 1987 , but through its widespread adoption has also come to mean either an analog computer display standard, the 15-pin D-subminiature VGA connector, or the 640×480 resolution itself. While this resolution has been superseded in the personal computer market, it is becoming a popular resolution on mobile devices
VGA was the last graphical standard introduced by IBM that the majority of PC clone manufacturers conformed to, making it today (as of 2008) the lowest common denominator that all PC graphics hardware supports before a device-specific driver is loaded into the computer. For example, the Microsoft Windows splash screen appears while the machine is still operating in VGA mode, which is the reason that this screen always appears in reduced resolution and color depth.
VGA was officially superseded by IBM's XGA standard, but in reality it was superseded by numerous slightly different extensions to VGA made by clone manufacturers that came to be known collectively as "Super VGA".

VGA is referred to as an "array" instead of an "adapter" because it was implemented from the start as a single chip, replacing the Motorola 6845 and dozens of discrete logic chips covering a full-length ISA board that the MDA, CGA, and EGA used. This also allowed it to be placed directly on a PC's motherboard with a minimum of difficulty (it only required video memory, timing crystals and an external RAMDAC), and the first IBM PS/2 models were equipped with VGA on the motherboard.
The VGA specifications are as follows:

• 256 KB Video RAM
• 16-color and 256-color modes
• 262,144-value color palette (six bits each for red, green, and blue)
• Selectable 25.175 MHz or 28.3 MHz master clock
• Maximum of 720 horizontal pixels
• Maximum of 480 lines
• Refresh rates at up to 70 Hz
• Vertical Blanking interrupt (Not all clone cards support this.)
• Planar mode: up to 16 colors (4 bit planes)
• Packed-pixel mode: 256 colors (Mode 13h)
• Hardware smooth scrolling support
• Some "Raster Ops" support
• Barrel shifter
• Split screen support
• 0.7 V peak-to-peak
• 75 ohm double-terminated impedance (18.7mA - 13mW)

The VGA supports both All Points Addressable graphics modes, and alphanumeric text modes. Standard graphics modes are

• 640×480 in 16 colors
• 640×350 in 16 colors
• 320×200 in 16 colors
• 320×200 in 256 colors (Mode 13h)

As well as the standard modes, VGA can be configured to emulate many of the modes of its predecessors (EGA, CGA, and MDA).
The pinout can be found in the VGA connector page.

DVI

The Digital Visual Interface (DVI) is a video interface standard designed to maximize the visual quality of digital display devices such as flat panel LCD computer displays and digital projectors. It was developed by an industry consortium, the Digital Display Working Group (DDWG). It is designed for carrying uncompressed digital video data to a display. It is partially compatible with the High-Definition Multimedia Interface (HDMI) standard in digital mode (DVI-D).

The DVI interface uses a digital protocol in which the desired illumination of pixels is transmitted as binary data. When the display is driven at its native resolution, it will read each number and apply that brightness to the appropriate pixel. In this way, each pixel in the output buffer of the source device corresponds directly to one pixel in the display device, whereas with an analog signal the appearance of each pixel may be affected by its adjacent pixels as well as by electrical noise and other forms of analog distortion.
Previous standards such as the analog VGA were designed for CRT-based devices and thus did not use discrete time display addressing. As the analog source transmits each horizontal line of the image, it varies its output voltage to represent the desired brightness. In a CRT device, this is used to vary the intensity of the scanning beam as it moves across the screen.
DVI cable connectors are designed in such a way as not to allow the user to connect the cable in an incorrect position or orientation. DVI connectors are available in five models, differing in the way they handle analog or digital transfers. In the digital transfer one or two channels are present. Video and monitor cards which are exclusively digital cannot be connected to analog, but can be connected to equipment that handles both analog and digital signals. The DVI standard also supports the Display Data Channel (DDC) and the Extended Display Identification Data (EDID), which allows computers to communicate with different monitor extensions.
"DVI-I" stands for "DVI-Integrated" and supports both digital and analog transfers, so it works with both digital and analog monitors. "DVI-D" stands for "DVI-Digital" and supports digital transfers only.

The data format used by DVI is based on the PanelLink serial format devised by the semiconductor manufacturer Silicon Image Inc. This uses Transition Minimized Differential Signaling (TMDS). A single DVI link consists of four twisted pairs of wire (red, green, blue, and clock) to transmit 24 bits per pixel. The timing of the signal almost exactly matches that of an analog video signal. The picture is transmitted line by line with blanking intervals between each line and each frame, and without packetization. No compression is used and there is no support for only transmitting changed parts of the image. This means that the whole frame is constantly re-transmitted. The specification (see below for link) does, however, include a paragraph on "Conversion to Selective Refresh" (under 1.2.2), suggesting this feature for future devices.
With a single DVI link, the largest resolution possible at 60 Hz is 2.75 megapixels (including blanking interval). For practical purposes, this allows a maximum screen resolution at 60 Hz of 1915 x 1436 pixels (standard 4:3 ratio), 1854 x 1483 pixels (5:4 ratio) or 2098 x 1311 (widescreen 8:5 ratio). The DVI connector therefore has provision for a second link, containing another set of red, green, and blue twisted pairs. When more bandwidth is required than is possible with a single link, the second link is enabled, and alternate pixels may be transmitted on each, allowing resolutions up to 4 megapixels at 60 Hz. The DVI specification mandates a fixed single link maximum pixel clock frequency of 165 MHz, where all display modes that require less than this must use single link mode, and all those that require more must switch to dual link mode. When both links are in use, the pixel rate on each may exceed 165 MHz. The second link can also be used when more than 24 bits per pixel is required, in which case it carries the least significant bits. The data pairs carry binary data at ten times the pixel clock reference frequency, for a maximum data rate of 1.65 Gbit/s x 3 data pairs for a single DVI link.
Like modern analog VGA connectors, the DVI connector includes pins for the display data channel (DDC). DDC2 (a newer version of DDC) allows the graphics adapter to read the monitor's extended display identification data (EDID). If a display supports both analog and digital signals in one input, each input can host a distinct EDID. If both receivers are active, analog EDID is used.
The maximum length of DVI cables is not included in the specification since it is dependent on bandwidth requirements (the resolution of the image being transmitted). In general, cable lengths up to 4.5 m (15 ft) will work for displays at resolutions of 1920 x 1200. Cable lengths up to 15 m (50 ft) can be used with displays at resolutions up to 1280 x 1024. For longer distances, to eliminate the video degradation, the use of a DVI booster is recommended. DVI boosters may or may not use an external power supply.

The DVI connector usually contains pins to pass the DVI-native digital video signals. In the case of dual-link systems, additional pins are provided for the second set of data signals.
As well as digital signals, the DVI connector includes pins providing the same analog signals found on a VGA connector, allowing a VGA monitor to be connected with a simple plug adapter. This feature was included in order to make DVI universal, as it allows either type of monitor (analog or digital) to be operated from the same connector.
The DVI connector on a device is therefore given one of three names, depending on which signals it implements:

• DVI-D (digital only)
• DVI-A (analog only)
• DVI-I (integrated, digital & analog)

The connector also includes provision for a second data link for high resolution displays, though many devices do not implement this. In those that do, the connector is sometimes referred to as DVI-DL (dual link).
The long flat pin on a DVI-I connector is wider than the same pin on a DVI-D connector, so it is not possible to connect a male DVI-I to a female DVI-D by removing the 4 analog pins. It is possible, however, to connect a male DVI-D cable to a female DVI-I connector. Many flat panel LCD monitors have only the DVI-D connection so that a DVI-D male to DVI-D male cable will suffice when connecting the monitor to a computer's DVI-I female connector.
DVI is the only widespread video standard that includes analog and digital transmission options in the same connector. Competing standards are exclusively digital: these include a system using low-voltage differential signaling (LVDS), known by its proprietary names FPD (for Flat-Panel Display) Link and FLATLINK; and its successors, the LVDS Display Interface (LDI) and OpenLDI.
Some new DVD players, TV sets (including HDTV sets) and video projectors have DVI/HDCP connectors; these are physically the same as DVI connectors but transmit an encrypted signal using the HDCP protocol for copy protection. Computers with DVI video connectors can use many DVI-equipped HDTV sets as a display; however, due to Digital Rights Management, it is not clear whether such systems will eventually be able to play protected content, as the link is not encrypted.
USB signals are not incorporated into the connector, but were earlier incorporated into the VESA Plug and Display connector used by InFocus on their projector systems, and in the Apple Display Connector, which was used by Apple Computer until 2005.
The DMS-59 connector is a way to combine two analog and two digital signals in one plug. It is commonly used when a single graphics card has two outputs.
M1-DA connectors are sometimes labeled as DVI-M1; they are used for the VESA Enhanced Video Connector and VESA Plug and Display schemes.

HDMI

The High-Definition Multimedia Interface (HDMI) is a compact audio/video connector interface for transmitting uncompressed digital streams. It represents a digital alternative to consumer analog standards such as Radio Frequency (RF) coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, and VGA. HDMI connects digital audio/video sources such as set-top boxes, Blu-ray Disc players, personal computers, video game consoles, and AV receivers to compatible digital audio devices, computer monitors, and digital televisions.
HDMI supports, on a single cable, any TV or PC video format including standard, enhanced, and high-definition video along with up to 8 channels of digital audio. It is independent of the various digital television standards such as ATSC and DVB as these are encapsulations of compressed MPEG video streams (which can be decoded and output as uncompressed video stream on HDMI).
HDMI products started shipping in autumn 2003 and currently over 800 CE and PC companies have adopted the HDMI specification (HDMI Adopters). HDMI began to appear on consumer HDTV camcorders and digital still cameras in 2006. Shipments of HDMI are expected to exceed that of Digital Visual Interface (DVI) in 2008, driven primarily by the Consumer Electronics (CE) Market.

HDMI supports, on a single cable, any TV or PC video format including standard, enhanced, and high-definition video along with up to 8 channels of digital audio. HDMI encodes the video data into TMDS for uncompressed digital transmission over HDMI.
HDMI devices are manufactured to adhere to various versions of the specification, where each version is given a number such as 1.0, 1.2, or 1.3a. Each subsequent version of the specification uses the same kind of cable but increases the bandwidth and/or capabilities of what can be transmitted over the cable. For example the previous maximum pixel clock rate of HDMI interface was 165 MHz which was sufficient for supporting 1080p at 60 Hz and WUXGA (1920x1200) at 60 Hz. HDMI 1.3 increased that to 340 MHz which allows for higher resolution, such as WQXGA (2560x1600), across a single digital link.
HDMI supports 8 channel uncompressed digital audio at 192 kHz sample rate with 24 bits/sample as well as compressed audio streams such as Dolby Digital and DTS. HDMI supports up to 8 channels of one-bit DSD audio, which is used on Super Audio CDs, at rates up to 4x that of Super Audio CD. With version 1.3, HDMI also supports lossless compressed audio streams such as Dolby TrueHD and DTS-HD Master Audio.
In the U.S., HDCP support is a standard feature on digital TVs while in the PC industry it is becoming more common but still depends on the specific model. The first computer monitors with HDCP support started being released in 2005 and by February 2006 a dozen had been released.
PCs with HDMI output using Windows Vista and Windows XP may be capable of HDMI audio output depending on specific hardware. For example Intel's motherboard chipsets since the 945G have been capable of 7.1 channel LPCM output over HDMI. Linux currently supports HDMI video output through backward compatibility with DVI.