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DDC (Display Data Channel)

What Are EDID Emulators And How They Help AV Signal Distribution

Black Box Explains

For your display screen, TV or projector to show the best picture possible, it must be able to communicate its capabilities with the video source. EDID, or extended display identification data, is the data structure your display uses for this communication.

What Is EDID (Extended Display Identification Data) And Why Is It Important?

EDID is a VESA standard data format that contains information about the display’s manufacturer, screen size, native resolution, color characteristics, frequency range limits and more. Once the source receives this information, it can then generate the necessary video characteristics to match the needs of the display. EDID is often used with a computer graphics card as the source device. Additionally, HDTV receivers, DVD and Blu-Ray players, LCD displays and digital TVs can read EDID and output the required video format.

What Is DDC (Display Data Channel)?

DDC (Display Data Channel) is a defined Standard by VESA. While DDC is just the description of the interface, the true data that is exchanged between graphic adapter card and monitor is called EDID (Extended Display Information Data). This data exchange is for identification of the attached screens and to read their video specifications mainly. Optimum resolutions and maximum resolutions as well as Gamma values part of this protocol. If a monitor is directly attached to a graphic adapter card the only concern is to have a connection cable that supports DDC transmission (VGA: pins 12 an 15 need to be connected).

How Is EDID Data Exchanged? The Relation Between EDID And DDC

EDID is transmitted between the source device and the display through a display data channel, or DDC, which is a collection of digital communication protocols created by the Video Electronics Standards Association (VESA). With EDID providing the display information and DDC providing the physical link between the display and the source, the two accompanying standards enable a plug-and-play experience for information exchange between display and source. For EDID information to be available at the source, all your display device connections must support DDC—including your extenders, switches, cables, splitters, amplifiers, repeaters and converters. If one or more connections in the chain does not support DDC, the display could show the wrong colors, size or position, or it might show nothing at all.

How Important Is EDID Emulation And That KVM Switches Support EDID

KVM Extenders enable the transmission of video data over long distances, whereas KVM Switches provide connectivity between multiple sources and one set of screen and peripherals or vice versa. Both technologies act as a connection intermediary between one or multiple video sources and displays. Most of the latest digital KVM devices support EDID exchange, yet some analog VGA KVM devices may require special attention and if necessary additional help from EDID Ghost Emulators (additional information below).

KVM devices supporting EDID management allow implementing it in one of three ways.

  1. The first is pass-through EDID, which involves transferring data directly from a source to the display. Pass-through EDID is often used in video and KVM extenders.
  2. A second type of EDID management is built-in EDID. In this scenario, the extender contains an internal EDID data table and can send data back to the source. It learns from the output device and can emulate it. This type is often used in AV/IT systems with single or multi-display configurations.
  3. The third EDID management method is EDID learning, in which the extender can capture data from a single attached display or compile data from all attached displays. EDID learning is ideal for configurations with multiple displays that don’t share the same native resolution or aspect ratio.

Benefits Of Using EDID Emulators When Extending AV Signals

Passing EDID information when extending signals is a very important feature for your extenders because it:

  • allows your computer to detect displays that are connected to it, enabling plug-and-play capabilities
  • eliminates the need to manually configure displays
  • reduces potential for incorrect settings that might compromise the quality of the display or the reliability of the system
  • optimizes the display to the fullest capability of the video card

With an EDID emulator, you are able to capture EDID information from the monitor and have it available to the PC regardless of cable types or other problems present in the installation.

Connecting a DVI EDID Ghost

Signal Extension With EDID Pass-Through

Sometimes display problems occur because of signal strength issues, incorrect communication between the display and the source, or even missing EDID transmission support. To troubleshoot these situations, you can use an EDID Ghost Emulators. This unit enables copying, emulating, cloning and learning of EDID from a display. The EDID Ghost Emulator units available from BlackBox records and stores up to 15 different sets of EDID.

Contact Black Box

Black Box offers a range of EDID/DDC-compatible equipment as well as the EDID Ghost Emulators. Contact us to find the right solutions for your applications.