Saturday, October 8, 2011


A male DVI-D (single link) connector
Digital Visual Interface (DVI) supports Extended Display Identifi cation Data (EDID), a dedicated data stream that allows a display to communicate its capabilities to the graphics source through the DDC (Data Display Channel). The DDC's I2C master in the DVI-source reads EDID from the display device's I2C slave.

EDID is defined by a standard published by the Video Electronics Standards Association (VESA). The EDID 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.

EDID structure versions range from v1.0 to v1.4; all these define upwards-compatible 128-byte structures. EDID structure v2.0 defined a new 256-byte structure, but subsequently has been deprecated and replaced by v1.3. HDMI 1.0 – 1.3c uses EDID structure v1.3.

With EDID, the display communicates its operational information to the graphics source including available resolutions and scan rates. Ideally, the graphics card will read the EDID and adjust its output to best match the native resolution and scan rate of the display, avoiding any compromises in image quality due to scaling, scan rate conversion, etc. More importantly, the graphics source must receive the EDID info in order to send a signal. If the EDID is lost, the graphics source must shut down within 1 second. This is to avoid the assumed disconnected end of the DVI cable becoming a high-frequency radiator that could cause radio
frequency interference.

The following presentations provide very helpful information for EDID usage:
The most critical EDID setting is the timing which consists of
  • Resolution (e.g. 640x480, 1280x1024, 1920x1200)
  • This is the dominant characteristic which also defines the display capability
  • Vertical or refresh rate (e.g. 60Hz, 75Hz, 85Hz)
  • Horizontal rate (or line rate)
  • Blanking
  • Sync

No comments:


Blog Archive

About Me

My photo
HD Multimedia Technology player