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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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implementing edid that works
Implementing EDID That Works

Neal Kendall & Jeff Stenhouse

edid presentation overview
EDID Presentation Overview
  • EDID Overview
  • EDID Operation
  • Implementing EDID
  • EDID compliance
edid overview
EDID Overview
  • Common Terms
    • EDID “Extended Display Identification Data”
    • E-EDID “Enhanced…”
    • VESA “Video Electronics Standards Association”
    • DDC is a term used to describe the EDID data structure and I2C bus protocol
  • What is an EDID?
    • EDID is a VESA creation to support Plug & Play
    • A data structure residing in a display or repeater; stored in 128 byte blocks
    • EDIDs contain a lot of data in a very small size; the data is densely stored
      • Data stored in bit format where values are binary in nature
      • Data stored in byte format using hex encoding
      • Sometimes values are truncated
      • Data is stored in an abbreviated form
  • What is the purpose of an EDID?
    • A display’s way of describing its identity and capabilities to a source, e.g.: video formats, audio formats, colorimetry, lip-sync delays, etc.
    • Source (graphics card, DVD, STB, etc) can then select output (e.g. video formats) in accordance with what display supports
    • Two modes:
      • Pass-through – when DTV supports the format that the content uses
      • Scaling and scan conversion is required when DTV does not support format of the content – source converts video output to the preferred format
edid overview edid versions









DTV (newer)

Source (older)


EDID Overview – EDID Versions
  • EDID block structure in HDMI displays
    • VESA block (Block 0) is required
    • At least one CEA extension block is required
    • If more than one extension block is used they must all be the same version
  • VESA EDID Versions
    • Version 1.3 (Version 1; Revision 3)
      • Version 1.3 is the required EDID structure for CEA-861D-based HDMI displays
      • E-EDID is based on VESA version 1.3; supports extensions
      • Current version of E-EDID is Release A; Revision 1 (2000)
  • CEA EDID extension versions
    • Defined in CEA-861D
    • HDMI monitors require version 3 of the CEA extension in their EDID data structure
  • Backward compatibility facilitated by:
    • New EDIDs implemented in a display must include all fields of past EDID versions
    • EDIDs include length fields for data block so older sources can skip newer data blocks they don’t understand
    • Inclusion of Detailed Timing Descriptors
overview cea extension for hdmi ce equipment



Overview – CEA Extension for HDMI CE Equipment
  • Enhancements with CEA extension version 3
    • Includes the ability to specify any of the CEA video formats as short video descriptors
    • Includes the ability to specify advanced audio formats as short audio descriptors
    • Provides a way for the sink device to specify its speaker configuration with multi-channel audio
    • Requires that a DTV protect its EDID against accidental corruption (write protected)


edid operation hot plug

Hot Plug Detect


EDID Operation – Hot Plug
  • The EDID is transmitted over the HDMI DDC bus based on I2C protocol
  • Hot plug assertion is an indication by the display that the EDID is available
  • The EDID is transmitted over the HDMI DDC bus based on I2C protocol
  • Hot plug assertion is an indication by the display that the EDID is available (even if display is Off)
  • Hot plug assertion should always initiate an EDID read

Quantum Data's Auxiliary Channel Analyzer






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

vesa block header
VESA Block - Header

Quantum Data's EDID Editor Utility

vesa block edid version revision
VESA Block - EDID Version/Revision

EDID 1.3 is required to support the CEA extension. (Note: 1.4 is available but not recognized by HDMI)

vesa block color characteristics

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.

vesa block established timings
VESA Block - Established Timings

Established timings are computer display timings that predate EDID but are recognized by VESA.

vesa block standard timing identification
VESA Block - Standard Timing Identification

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.

vesa block timing descriptor

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

vesa block monitor descriptor
VESA Block - Monitor Descriptor

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

vesa block monitor range limits descriptor
VESA Block - Monitor Range Limits Descriptor

Applies to CRT based multi-scan systems and not flat panel or most CE equipment

vesa block extension flag
VESA Block - Extension Flag

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.

vesa block checksum
VESA Block – Checksum

A source should re-read a display’s EDID if there is an error in the checksum.

cea block cea formats
CEA Block – CEA Formats
  • CEA-861-D formats
  • 640x480p @59.94/60 Hz (Format 1)
  • 1280x720p @59.94/60 Hz (Format 4)
  • 1920x1080i @59.94/60 Hz (Format 5)
  • 720x480p @59.94/60 Hz (Formats 2 & 3)
  • 720(1440)x480i @59.94/60 Hz (Formats 6 & 7)
  • 1280x720p @ 50 Hz (Format 19)
  • 1920x1080i @ 50 Hz (Format 20)
  • 720x576p @ 50 Hz (Formats 17 & 18)
  • 720(1440)x576i @ 50 Hz (Formats 21 & 22)
  • 720(1440)x240p @ 59.94/60 Hz (Formats 8 & 9)
  • (2880)x480i @ 59.94/60 Hz (Formats 10 & 11)
  • (2880)x240p @ 59.94/60 Hz (Formats 12 & 13)
  • 1440x480p @ 59.94/60 Hz (Formats 14 & 15)
  • 1920x1080p @ 59.94/60Hz (Format 16)
  • 720(1440)x288p @ 50 Hz (Formats 23 & 24)
  • (2880)x576i @ 50Hz (Formats 25 & 26)
  • (2880)x288p @ 50 Hz (Formats 27 & 28)
  • 1440x576p @ 50Hz (Formats 29 & 30)
  • 1920x1080p @ 50 Hz (Format 31)
  • 1920x1080p @ 23.98/24 Hz (Format 32)
  • 1920x1080p @ 25 Hz (Format 33)
  • 1920x1080p @ 29.97/30 Hz (Format 34)
  • 2880x480p @ 59.94/60 Hz (Formats 35 and 36)
  • 2880x576p @ 50 Hz (Formats 37 and 38)
  • 1920x1080i (1250 Total) @ 50 Hz (Format 39)
  • 1920x1080i @ 100 Hz (Format 40)
  • 1280x720p @ 100 Hz (Format 41)
  • 720x576p @ 100 Hz (Formats 42 and 43)
  • 720(1440)x576i @ 100 Hz (Formats 44 and 45)
  • 1920x1080i @ 119.88/120 Hz (Format 46)
  • 1280x720p @ 119.88/120 Hz (Format 47)
  • 720x480p @ 119.88/120 Hz (Formats 48 and 49)
cea block structure
CEA Block – Structure






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


cea block extension tag
CEA Block - Extension Tag

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.

cea block byte 3
CEA Block - Byte 3

In HDMI, any display that supports YCbCr must support both 4:4:4 and 4:2:2 sampling. All displays have to support RGB

cea block video data block descriptors

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

Header Byte

4 F

Short Video Descriptor

0 1 0 0 1 1 1 1

8 5

1 0 0 0 0 1 0 1

Type = 2 Length = 15

Vic Code = 5


CEA Block - Video Data Block Descriptors
edid operation extended tag operation






EDID Operation – Extended Tag Operation
  • Repeater devices may pass EDID data blocks from DTV upstream, if…
    • DTV has video data block extended tag types
    • repeater retransmits video from source to DTV without modifying of video timing or data



cea block audio data block descriptors

Header Byte

Descriptor 3 - Byte 2

Descriptor 3 - Byte 1

2 F

1 5

0 7

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

3 8

0 0 1 1 0 1 1 1

Max bit rate / 8k 38h (56) * 8k = 448k

CEA Block - Audio Data Block Descriptors

If only basic audio is supported, Short Audio Descriptors are not necessary

Short audio descriptors are 3 bytes each

cea block speaker allocation block

Descriptor 3 - Byte 2

0 F

0 0 0 0 1 1 1 1


CEA 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.

cea block vendor specific block


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.

cea block vsdb cec physical addressing
CEA Block – VSDB CEC Physical Addressing

Physical Address assigned by downstream device (TV side) from the Source Physical Address fields of the downstream devices EDID VSDB.

cea block timing descriptor

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
edid compliance testing
EDID Compliance Testing
  • Part of HDMI Compliance Test specification
  • Capabilities Declaration Form identifies which test are run during execution (compiled test suite)
  • Test Execution and report
edid compliance testing33

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 EDID

EDID Compliance Testing

Quantum Data's EDID Compliance Test Application