Implementing EDID That Works Neal Kendall & Jeff Stenhouse EDID Presentation Overview EDID Overview EDID Operation Implementing EDID EDID compliance EDID Overview Common Terms EDID “Extended Display Identification Data” E-EDID “Enhanced…” VESA “Video Electronics Standards Association”
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Neal Kendall & Jeff Stenhouse
HDMI (DDC)EDID Overview – EDID Versions
SourceOverview – CEA Extension for HDMI CE Equipment
DDCEDID Operation – Hot Plug
Quantum Data's Auxiliary Channel Analyzer
HDMI DDC (I2C)
EDID read can occur either as a full read of block 0 and 1 or read independently
An EDID read is initiated by hot plug
Quantum Data's EDID Editor Utility
EDID 1.3 is required to support the CEA extension. (Note: 1.4 is available but not recognized by HDMI)
Calculation example:A0 = .625…
1010 0000 00
2^-1 + 2^-3 = 0.625
Low order bits stored here (19h, 1Ah)VESA Block - Color Characteristics
Identifies the color characteristics. Each color is stored in a 10 bit value.
Established timings are computer display timings that predate EDID but are recognized by VESA.
Standard timings are timings that are recognized by VESA through the VESA Discrete Monitor Timing or Generalized Timing Formula standards. Accommodates future standard timings.
CE devices may not support VESA timings (except 640x480p format), therefore standard timings may not be declared or used; unused bytes are filled with 01h.
The “Preferred” video format is typically the one closest to the native resolution of the display. The native resolution is the number of pixels on the display panel.
The VESA E-EDID Standard requires that the First Detailed Timing Descriptor be the “preferred” video format and subsequent detailed timing descriptors listed in order of decreasing preference.
All four Detailed Timing Descriptors blocks are required to be filled with valid data, even if timing descriptor need to be repeated. No fill patterns.VESA Block - Timing Descriptor
For vertical timing with interlaced fields, Field 1 is listed. Field 2 is understood to be Field 1 + 1
Pixel clock field (36h and 37h) = Pixel clock / 10,000 in hex: 74250000 / 10,000 = 7425d -> 1D01h
Horizontal blanking field (39h) = Lower 8 bits in hex. 280d-> 118h
Avoid dependency on data in these descriptors as future use is possible.
The Detailed Timing Descriptors have to precede the two required Monitor Descriptors.
Uses ASCII encoding;
example 53 = S
Applies to CRT based multi-scan systems and not flat panel or most CE equipment
The extension flag is the number of extension blocks including the block 1 block map. The extension flag is used if there are more than one extension blocks.
Any HDMI monitor must include the version 3 or higher CEA extension block.
A source should re-read a display’s EDID if there is an error in the checksum.
Identifies type of extension
Revision # of extension
Define scanning, sampling, DTDs
General video information
Identifies where DTDs begin
Detailed Timing Descriptor (DTD) Block Offset
Identifies supported video formats with short video descriptors
Video Data Block
Identifies supported audio formats besides basic w/ short audio descriptors
Audio Data Block
Identifies supported speaker configurations for multi-channel audio
Blocks(can be in any order)
Speaker Allocat’n Data Block
Identifies vendor with IEEE codeprovides physical address upstream
Vendor Specific Data Block
Indicates support of extended colorimetry standards, e.g. xvYCC
Colorimetry Data Block
Identifies over/underscanning behavior and alternate quantizing
Video Capability Data Block
Detailed Timing Descriptors
Defines formats in detailed listings
Fills out 128 byte block
Validates the data block
VESA has assigned Tag 2 to CEA for definition of the CEA extension
When more than one extension is required, the first extension or Block 1 is used as an index map that lists extension locations.
In HDMI, any display that supports YCbCr must support both 4:4:4 and 4:2:2 sampling. All displays have to support RGB
Any HDMI monitor must advertise all CEA video formats as Short Video Descriptors, even if they are also use Detailed Timing Descriptors.
All short video descriptors have to be listed in order of priority; the first listed format is the one identified as optimal.
Short video descriptors are 1 byte each
Short Video Descriptor
0 1 0 0 1 1 1 1
1 0 0 0 0 1 0 1
Type = 2 Length = 15
Vic Code = 5
PreferredCEA Block - Video Data Block Descriptors
Source Short Video Descriptors, even if they are also use Detailed Timing Descriptors.
EDIDEDID Operation – Extended Tag Operation
Header Byte Short Video Descriptors, even if they are also use Detailed Timing Descriptors.
Descriptor 3 - Byte 2
Descriptor 3 - Byte 1
0 0 1 0 1 1 1 1
0 0 0 0 0 1 1 1
0 0 0 1 0 1 0 1
Type = 1 Length = 15 (audio)
Sampling rates 48,44,32
Type = 2 MaxCh = 5+1 (AC3 Dolby Digital)
Descriptor 3 - Byte 3
0 0 1 1 0 1 1 1
Max bit rate / 8k 38h (56) * 8k = 448kCEA Block - Audio Data Block Descriptors
If only basic audio is supported, Short Audio Descriptors are not necessary
Short audio descriptors are 3 bytes each
Descriptor 3 - Byte 2 Short Video Descriptors, even if they are also use Detailed Timing Descriptors.
0 0 0 0 1 1 1 1
RC,RL/RR,FC,LFE,FL/FRCEA Block - Speaker Allocation Block
If the HDMI DTV Monitor supports multi-channel uncompressed digital audio as indicated in the Audio Data Block, then the Speaker Allocation Data Block has to be included.
1100 Short Video Descriptors, even if they are also use Detailed Timing Descriptors.CEA Block - Vendor Specific Block
Vendor specific data block enables source devices to determine that the display is HDMI and configure its output accordingly (not DVI).
Source Physical Address fields provide the CEC physical address for upstream CEC devices.
Physical Address assigned by downstream device (TV side) from the Source Physical Address fields of the downstream devices EDID VSDB.
Even though Short Video Descriptors are available in the Version 3 CEA Extension, Detailed Timing Descriptors are used to support backward compatibility with legacy sources.
Detailed timings have to be listed in priority order.CEA Block - Timing Descriptor
Select which timings are claimed to be supported in the display’s EDID.
Identifies whether ACP/ISRC packet infoframes are supported.
“Other” i.e. are these timings supported on the analog component outputs?
Primary aspect ratio, i.e. aspect ratio of the preferred timing. Either 16:9 or 4:3
Displays (DTVs) are typically CEC root devices unless they serve as a switch
Identifies whether basic audio is supported.
If unchecked, the test is run based on CTS 1.2a. New products must pass 1.3b.
Select which timings are claimed to be supported in the display’s EDID.
Identifies if DC fields are populated in EDID
Identifies if lipsync latency fields are populated in EDIDEDID Compliance Testing
Quantum Data's EDID Compliance Test Application