EDID

EDID, or Extended Display Identification Data, is a metadata format used by display devices to convey their capabilities to a video source, such as a computer graphics card or a Blu-ray player. The data is retrieved over the Display Data Channel (DDC), an I2C-based communication link on HDMI, DVI, VGA, and DisplayPort connections. By reading EDID, the source learns supported video modes, preferred timing, color characteristics, and other display attributes, enabling automatic resolution and refresh-rate negotiation and ensuring proper color rendering.

An EDID data set consists of a 128-byte base block plus optional extension blocks. The base block contains device identifiers (manufacturer ID, product code, serial number), the EDID version, basic display parameters (screen size information, gamma), and a collection of timing descriptors that describe supported resolutions and refresh rates. Extension blocks can augment the data; the most common is the CEA-861 extension, which lists consumer electronics video formats, audio capabilities, speaker allocation, and additional timing data.

Versions and usage: The most widely deployed versions are EDID 1.3/1.4. Many displays also provide additional features through extensions or vendor-specific data blocks. Operating systems and graphics drivers often cache EDID data and may apply overrides or user configurations.

Limitations: EDID information may be incomplete or inaccurate if the display is misreported or corrupted. In such cases the source can fall back to predefined safe modes or user-specified settings. EDID can also be spoofed or overridden by devices that wish to force a particular output mode, though this is not standard behavior.