Extended Display Identification Data (EDID) and Enhanced EDID (E-EDID) are metadata formats for display devices to describe their capabilities to a video source (e.g., graphics card or set-top box).
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.
Version 2.0 defined a new 256-byte structure but it has been deprecated and replaced by E-EDID which supports multiple extension blocks.
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.
This problem is solved by EDID and DDC, as it enables the display to send information to the graphics card it is connected to.
The transmission of EDID information usually uses the Display Data Channel protocol, specifically DDC2B, which is based on I²C-bus (DDC1 used a different serial format which never gained popularity).
The data is transmitted via the cable connecting the display and the graphics card; VGA, DVI, DisplayPort and HDMI are supported.
[citation needed] The EDID is often stored in the monitor in the firmware chip called serial EEPROM (electrically erasable programmable read-only memory) and is accessible via the I²C-bus at address 0x50.
The EDID PROM can often be read by the host PC even if the display itself is turned off.
Data fields for preferred timing, range limits, and monitor name are required in E-EDID.
E-EDID also adds support for the Dual GTF curve concept and partially changed the encoding of aspect ratio within the standard timings.
With the use of extensions, E-EDID structure can be extended up to 32 KiB, because the E-DDC added the capability to address multiple (up to 128) 256 byte segments.
The number of vertical pixels is calculated from the horizontal resolution and the selected aspect ratio.
Special programs are available to override the standard timing descriptors from EDID data.
00 = Default GTF (when basic display parameters byte 24, bit 0 is set).
[14] Coinciding with the publication of CEA-861-F in 2013, Brian Markwalter, senior vice president, research and standards, stated: "The new edition includes a number of noteworthy enhancements, including support for several new Ultra HD and widescreen video formats and additional colorimetry schemes.”[15] Version CTA-861-G,[16] originally published in November 2016, was made available for free in November 2017, along with updated versions -E and -F, after some necessary changes due to a trademark complaint.
It combines the previous version, CTA-861-H,[20] from January 2021 with an amendment, CTA-861.6,[21] published in February 2022 and includes a new formula to calculate Video Timing Formats, OVT.
[22] Other changes include a new annex to elaborate on the audio speaker room configuration system that was introduced with the 861.2 amendment, and some general clarifications and formatting cleanup.
It contains updates to CTA 3D Audio, and clarifications on Content Type Indication, and on 4:2:0 support for VTDBs and VFDBs.
Version 2 (as defined in 861-A) added the capability to designate a number of DTDs as "native" (i.e., matching the resolution of the display) and also included some "basic discovery" functionality for whether the display device contains support for "basic audio", YCBCR pixel formats, and underscan.
Version 3 also defines a format for a collection of data blocks, which in turn can contain a number of individual descriptors.
Notes: Parentheses indicate instances where pixels are repeated to meet the minimum speed requirements of the interface.
As VESA DMT specifies 0.5% pixel clock tolerance, which 5 times more than the required change, pixel clocks can be adjusted to maintain NTSC compatibility; typically, 240p, 480p, and 480i modes are adjusted, while 576p, 576i and HDTV formats are not.
Each SAD details audio format, channel number, and bitrate/resolution capabilities of the display as follows: A Vendor Specific Data Block (if any) contains as its first three bytes the vendor's IEEE 24-bit registration number,[24] least significant byte first.