Digital Visual Interface
Digital Visual Interface (DVI) [ dɪdʒɪtəl vɪʒuəl ɪntəfeɪs ] is an electronic interface for the transmission of video data. In the computer field, DVI is developed as a standard for connection of TFT monitors to the graphics card of a computer. There are TVs that process with a DVI input signals from digital sources such as computer or DVD player. In consumer electronics, the HDMI interface is much more widespread. HDMI is an evolution of DVI; For more information about backward compatibility, see below.
DVI allows the simultaneous transmission of analogue and digital image data.
Signal transmission
For digital data transfer uses the standard DVI TMDS. Here, the usual 8 bits of an RGB signal is transmitted serially - if necessary by a serializer, which is connected by means of Double Data Rate function. When establishing a connection is negotiated, whether a single-link connection ( max. 3.72 Gbit / s over 3 pairs ) or a dual-link connection (up to 7.44 Gbit / s over 6 pairs ) will be used. In addition, resolution, bit depth, frame rate, and encryption to be negotiated. Pixel frequencies above 165 MHz or bit depths greater than 8 bits ( per pixel and color) always require a dual-link connection.
The negotiation is done by connecting the monitor next to its manufacturer, model, serial number and Farbkalibrierdaten its supported video modes via DDC tells the computer. The computer sends to another video format is often no picture shown.
The transient response of the cable reduces the achievable bandwidth. The possible resolution with single-link cables therefore include, for example at 60 Hz 1600 × 1200 pixels (UXGA ), or even 1920 × 1200 ( WUXGA ), if the graphics card and monitor Reduced blanking support. In dual-link cables thanks to the double number of data lines, a doubling of the number of pixels is possible. This results in an increase in the horizontal and vertical resolution by the factor. By reducing the frame rate even higher resolutions are possible. This would lead to flicker in CRT monitors, which inherently does not occur in LCD monitors.
The digital data transmission usually result quality advantages over the ( analog ) connection to a VGA or SCART cable. In the latter two transmission methods ( unnecessary with digital screens ) signal conversions are necessary: from digital to analog on the video output, and back from analog to digital in the monitor. Accordingly, maturities in electronics strongly affects.
The maximum cable length when connecting a DVI terminal ( monitor) depends on the attenuation and crosstalk in the connecting line and the quality of the signal amplification. So should not exceed a maximum cable length of 10 meters. With greater line length a DVI amplifier between two cable sections should be used. With analog transmission, the image is blurred due to insufficient signal quality at the end of the cable; in digital transmission interrupts processing of the incoming signal due to high bit error rates together completely.
Mini - DVI and Micro- DVI Apple MacBook Air are just mechanically different variants.
Pin assignment
Depending on the pin assignment of a DVI connection may transmit signals that analog (DVI -A ), digital (DVI -D), or analog and digital (DVI -I). It is also possible to transmit two digital signals at the same time ( dual link), therefore higher resolutions are possible.
Not every graphics card or monitor use of their connection from the maximum transmission opportunities the DVI connector. For example, a monitor have a DVI - I socket, although only digital transmission is used, or a graphics card can have a dual-link connector, although no high resolutions are supported. The DVI-I dual link connector is then only used for all types of plugs fit.
DVI-I
DVI-I cables can transmit analog and digital signals and differ in the number of wired plug contacts. A simple DVI cable ( Single-Link) has 18 5 contacts and enough for Full HD 1920x1080 resolution at 60 Hz with 24 5 cable contacts have two TMDS links ( dual-link ) for high-resolution displays, such as WQXGA, maximum of 2560 × 1600 pixels at 60 Hz
The elongated ground pin of a DVI-I connector is wider than that of a DVI -D connector, so that a DVI-I connector can not be connected to a DVI -D socket, not even after removal of the four analog Contacts.
If a combined signal (DVI- I) to the DVI connector on the graphics card available, even an analog VGA monitor can be used with this socket using a purely passive adapter. Such a DVI-I to VGA adapter uses directly the analog and "plug and play " signals to the DVI port and makes them arranged according to the VGA standard. There are also cables that have VGA and DVI on one at the other end, technically do the same thing, but save a connecting element.
It is even possible to transmit digital audio over the DVI -I connector in addition by the use not provided for this purpose pins. This method is applied for example in the Dreambox models 800/8000 that do not have HDMI, but only a DVI connection. This mode of operation is not provided by the DVI standard, and the result is not a DVI -compliant signal.
DVI -D
DVI -D cable can only transmit digital signals and differ in the number of wired plug contacts. DVI -D cable ( Single-Link) have 18 1 (in rare cases, 17 1) contacts and range of Full HD 1920x1080 resolution at 60 Hz
DVI -D cable (Dual Link ) 24 1 Pins have a second TMDS link for a maximum of 2560 × 1600 pixels at 60 Hz (or 23 1 Pins, since most of the commercially available cables is not pin 8 be connected, even if they offered 24 1). Commercially also DVI-D cables are only 12 1 Pins, here no DDC data to be transmitted, so that the operating system the screen can not automatically detect it.
A DVI -D connector can be connected to a DVI - I socket.
DVI -A
DVI -A cable can only transmit analog signals. A DVI -A connector has 12 contacts 5. In practice DVI-A is only used as an adapter cable to VGA. DVI -A cable can also be used in DVI - I connectors, as these also allow the analog data transmission.
A passive VGA to DVI-A adapter transmits the analog signals from the graphics card via the DVI cable to the monitor. This must have a DVI - A input so that it can display the signals. The passive adapter can therefore not perform analog -to-digital conversion of the analog VGA signal; an improvement in quality of ( poorer ) analog signal by a " diversion" in the digital ( se better ) DVI cable is not reached.
DVI Connector
DVI -D socket ( dual link)
DVI -D socket ( dual link) with plug
Adapter DVI -A Male to VGA connector
Adapter HDMI Male to DVI Female (Dual -Link)
Future
In the field of entertainment electronics industry relies primarily on HDMI.
Some manufacturers of DVB receivers (eg Dream Multimedia ) and graphics card (AMD Radeon HD) transfer of not only high-resolution digital video data and digital audio data via the DVI connector. These signals are then compatible with HDMI.
DVI -D and DVI -I is upward compatible with HDMI, whereby all DVI-D to HDMI signals can be converted. Conversely, not all HDMI signals to DVI -D converter. For example, a copy protection such as HDCP for DVI -D is optional.
In computer to 2015 DisplayPort to VGA and DVI ports that support analog operation (DVI -I and DVI -A) to replace, and enable higher resolutions with greater color depth.