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http://www.x.org/wiki/XDC2007Notes#head-b6d8966522f55d527c81882e2ac5d3a3e1f8ec31 EDID is the mechanism by which monitors describe themselves. It's now technically called E-EDID since it's been extended, but it's still the same thing. EDID is now at version 1.4. Review of various display technologies in use today: CRT, LCD, plasma, projector, etc. Most fixed-pixel array displays have scalers. Newer and higher resolution displays have no pure scalers, so EDID becomes critical for driving them correctly. Review of display interfaces: VGA, DVI-{D,I}, HDMI, DisplayPort, UDI... A display may have many timings, CRTs for example are basically infinitely adaptable within their sync range. Some may have a few timings, or even only one. All cases are handled by EDID. The purpose of EDID is to make sure that _something_ comes up at power on. Signalling: Video content, blanking, sync, I2C digital signals for communication. Connector may carry other pins too (USB, audio, etc). (Timing math.) Timing specs include DMT, GTF, CVT. DMT was pages of explicit timings, GTF and CVT are formulas. Sync. Three main times: separate, where H and V can be positive or negative on independent pins; composite, where they're combined into one phase- coherent signal (unsupported but sometimes works for DVI); and sync-on-green, which is a DC-bias added to the green signal. Version table: 1.1 in 1996, 1.2 in 1997, 1.3 in 2000, 1.4 in 2006. 1.3 was the first that could handle extension blocks. Timing priority order: Preferred timing, other detailed timings in the base block, other detailed timings in the VTB-EXT, 3-byte CVT codes in base or extended blocks, standard timings, established timings, base video mode. Related vesa standards: CVT, DMT, DPM, DDC/CI, DPVL, MCCS, MDDI. DDC is the carrier channel for EDID. Coordinated Video Timings and Detailed Monitor Timings are various timing specs. DPM (successor to DPMS) is for Display Power Management. Basically, missing pulses on either or both sync pins plus inactive video means low power mode. DPMS was more complicated where there were standby and suspend modes between On and Off, depending on sync pin wiggling. Extensions: CEA, VTB, DI, LS, DPVL. (consumer electronics conformance, video timing block, display information, localised strings, and digital packet video link.) CEA is the DTV profile for uncompressed high speed digital video. DDC/CI allows for control of displays, basically anything you could do from the front panel and more. MCCS is the standard command set for DDC/CI. DPVL allows for only updating the regions of the screen that have changed. Lots of changes in EDID 1.4. (Will acquire slides for the list.) |
