Digital Visual Interface
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| Digital Visual Interface (DVI) | ||
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| Type | Digital and analog computer video connector | |
| Production history | ||
| Designer | Digital Display Working Group | |
| Designed | April 1999 | |
| Produced | 1999 to present | |
| Superseded | VGA connector | |
| Specifications | ||
| External | yes | |
| Video signal | Digital video stream. (Single) WUXGA 1920 × 1200 @ 60 Hz (Dual) WQXGA (2560 × 1600) @ 60 Hz Analog RGB video (-3 db at 400 MHz) |
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| Data signal | R,G,B data + clock and display data channel | |
| Bandwidth | (Single) 3.7 Gbit/s (Dual) 7.4 Gbit/s or more |
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| Max devices | 1 | |
| Protocol | 3 × Transition Minimized Differential Signaling data + clock | |
| Pins | 29 | |
| Pin out | ||
 A female DVI-I socket from the front |
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| Pin 1 | TMDS Data 2- | Digital red - (Link 1) |
| Pin 2 | TMDS Data 2+ | Digital red + (Link 1) |
| Pin 3 | TMDS Data 2/4 shield | |
| Pin 4 | TMDS Data 4- | Digital green - (Link 2) |
| Pin 5 | TMDS Data 4+ | Digital green + (Link 2) |
| Pin 6 | DDC clock | |
| Pin 7 | DDC data | |
| Pin 8 | Analog vertical sync | |
| Pin 9 | TMDS Data 1- | Digital green - (Link 1) |
| Pin 10 | TMDS Data 1+ | Digital green + (Link 1) |
| Pin 11 | TMDS Data 1/3 shield | |
| Pin 12 | TMDS Data 3- | Digital blue - (Link 2) |
| Pin 13 | TMDS Data 3+ | Digital blue + (Link 2) |
| Pin 14 | +5V | Power for monitor when in standby |
| Pin 15 | Ground | Return for pin 14 and analog sync |
| Pin 16 | Hot plug detect | |
| Pin 17 | TMDS data 0- | Digital blue - (Link 1) and digital sync |
| Pin 18 | TMDS data 0+ | Digital blue + (Link 1) and digital sync |
| Pin 19 | TMDS data 0/5 shield | |
| Pin 20 | TMDS data 5- | Digital red - (Link 2) |
| Pin 21 | TMDS data 5+ | Digital red + (Link 2) |
| Pin 22 | TMDS clock shield | |
| Pin 23 | TMDS clock+ | Digital clock + (Links 1 and 2) |
| Pin 24 | TMDS clock- | Digital clock - (Links 1 and 2) |
| C1 | Analog red | |
| C2 | Analog green | |
| C3 | Analog blue | |
| C4 | Analog horizontal sync | |
| C5 | Analog ground | Return for R, G and B signals |
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 primarily for carrying uncompressed digital video data to a display. It is partially compatible with the HDMI standard in digital mode (DVI-D).
Contents |
[edit] Overview
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.
However, when using digital displays (such as LCD) with analog signals (such as VGA), there is an array of discrete pixels and a single brightness value must be chosen for each. The decoder does this by sampling the voltage of the input signal at regular intervals. When the source is also a digital device (such as a computer), this can lead to distortion if the samples are not taken at the center of each pixel, and there are also problems with crosstalk.
[edit] Technical discussion
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 60Hz is 2.3 megapixels. 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 60Hz. The DVI specification mandates a fixed single link cutoff point 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.
Like modern analog VGA connectors, the DVI connector includes pins for the display data channel, version 2 (DDC 2) that allows the graphics adapter to read the monitor's extended display identification data (EDID).
[edit] Connector
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 (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).
DVI is the only widespread 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 signalling (LVDS), known by its proprietary names FPD (for Flat-Panel Display) Link and FLATLINK; and its successors, the LVDS Display Interface (LDI) and OpenLDI.
USB signals are not incorporated into the connector, but were ealrlier incorporated into the VESA M1-DA connector used by InFocus on their projector systems, and in the Apple Display Connector, which was used by Apple Computer until 2005. The VESA M1-DA connector is essentially the VESA Plug & Display (P&D) connector, which was itself originally named the Enhanced Video Connector (EVC). The pinout of the Apple Display Connector is electrically compatible with the VESA P&D/M1, but physically the shell of the connector is a different shape.
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.
The long flat pin on a DVI-I connector is longer 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.
[edit] Specifications
[edit] Digital
- Minimum clock frequency: 21.76 MHz
- Maximum clock frequency in single link mode: Capped at 165 MHz (3.7 Gbit/s)
- Maximum clock frequency in dual link mode: Limited only by cable quality (more than 7.4 Gbit/s)
- Pixels per clock cycle: 1 (single link) or 2 (dual link)
- Bits per pixel: 24
- Example display modes (single link):
- Example display modes (dual link):
GTF (General Timing Formula) is a VESA standard which can easily be calculated with the Linux gtf utility.
[edit] Analog
- RGB bandwidth: 400 MHz at -3 dB
[edit] See also
- ADC - Apple Display Connector, a similar, now-obsolete connector that can still be found on some older Macs. Based on DVI, with USB and power capabilities included.
- VGA connector analog video (an older standard, though very common on current computer hardware)
- High-Definition Multimedia Interface (HDMI), a forward-compatible standard, that also includes digital audio transmission
- Unified Display Interface (UDI), a proposed future standard to replace both DVI and HDMI
- DisplayPort, another proposed standard, incompatible with DVI and HDMI
- LCD TV
- DMS-59, a way to combine 2 analog and 2 digital signals in one connector
- DFP an older type of digital video link
[edit] External links
- The Digital Display Working Group
- Specification "Digital Visual Interface DVI", Revision 1.0, 02 April 1999
- DVI compatibility
| Audio and video connectors |
|---|
| Single conductor: Binding post | Banana plug | Fahnestock clip |
| Audio: RCA | Jack plug | XLR | DIN / Mini-DIN | BNC | DB25 | Speakon | TosLink |
| Video: DVI / Mini-DVI / UDI | RCA | VGA / Mini-VGA | DFP | BNC | DIN / Mini-DIN | 13W3 | D-Terminal | DisplayPort |
| Multi: ADC | P&D | HDMI | TRS | SCART | F | Belling-Lee | DisplayPort |
