Extended Display Identification Data

Extended Display Identification Data (EDID) is a metadata format for display devices to describe their capabilities to a video source (e.g. graphics card or set-top box). The data format is defined by a standard published by the Video Electronics Standards Association (VESA).

The EDID data structure includes manufacturer name and serial number, product type, phosphor or filter type, timings supported by the display, display size, luminance data and (for digital displays only) pixel mapping data.

DisplayID is a VESA standard targeted to replace EDID and E-EDID extensions with a uniform format suited for both PC monitor and consumer electronics devices.

Background

EDID structure versions range from v1.0 to v1.4; all these define upwards-compatible 128-byte structures. Version 2.0 defined a new 256-byte structure but it has been deprecated and replaced by v1.3 which supports multiple extension blocks.[citation needed] HDMI versions 1.0–1.3c use EDID structure v1.3.[1]

Before Display Data Channel (DDC) and EDID were defined, there was no standard way for a graphics card to know what kind of display device it was connected to. Some VGA connectors in personal computers provided a basic form of identification by connecting one, two or three pins to ground, but this coding was not standardized.

The channel for transmitting the EDID from the display to the graphics card is usually the I²C-bus, defined in DDC2B (DDC1 used a different serial format which never gained popularity).

The EDID is often stored in the monitor in a memory device called a serial PROM (programmable read-only memory) or EEPROM (electrically erasable PROM) and is accessible via the I²C-bus at address 0xA0. The EDID PROM can often be read by the host PC even if the display itself is turned off.

Many software packages can read and display the EDID information, such as read-edid[2] for Linux and DOS, PowerStrip[3] for Microsoft Windows and XFree86 for Linux and BSD unix. Mac OS X natively reads EDID information and programs such as SwitchResX[4] or DisplayConfigX[5] can display the information as well as use it to define custom resolutions.

Enhanced EDID was introduced at the same time as E-DDC; it introduced EDID structure version 1.3 which supports multiple extensions blocks and deprecated EDID version 2.0 structure (although it can be supported as an extension). Data fields for preferred timing, range limits, and monitor name are required in E-EDID. E-EDID also supports dual GTF timings and aspect ratio change.[clarification needed]

With the use of extensions, E-EDID string can be lengthened up to 32 KBytes.

EDID Extensions assigned by VESA

  • Timing Extension (00h)
  • Additional Timing Data Block (CEA EDID Timing Extension) (02h)
  • Video Timing Block Extension (VTB-EXT) (10h)
  • EDID 2.0 Extension (20h)
  • Display Information Extension (DI-EXT) (40h)
  • Localized String Extension (LS-EXT) (50h)
  • Microdisplay Interface Extension (MI-EXT) (60h)
  • Display ID Extension (70h)
  • Display Transfer Characteristics Data Block (DTCDB) (A7h, AFh, BFh)
  • Block Map (F0h)
  • Display Device Data Block (DDDB) (FFh)
  • Extension defined by monitor manufacturer (FFh): According to LS-EXT, actual contents varies from manufacturer. However, the value is later used by DDDB.