HDMI EDID Interpretation

Now display devices such as monitors, televisions and other HDMI interface, that usually each HDMI interface has a copy of the EDID data, this data can exist in the program is initialized by the system startup process, more common practice is that each HDMI port will have an EEPROM to save the data, This EEPROM is also only 256bytes in size. External devices, such as DVD players, can read EDID data through the HDMI DDC channel when HDMI is hot-swappable. EDID is mainly defined in this display device supported image resolution, supported sound formats, sound channels, and 3D, and so on, its purpose is to tell the external device I support the features, let the external device output a timing I support, Otherwise the external device output of the timing is not supported, then there is no image, the sound of the display.
EDID contains two parts, the basic edid is only 128 bytes, there are 128 bytes of extended edid, the extension is not necessary. That usually TV has an extended edid. The detailed definition of EDID can be found in the specification, mainly in the following parts:
(00h-07h) These 8 bytes are fixed and must be equal to 0x00ffffffffffffff00;
(08h-08h) the manufacturer's ID or name;
(0AH-0BH) Product ID;
(0CH-0FH) serial number;
(10h-11h) Production time;
(12h-13h) version number, such as 1.3 that is 01, 03;
(14H) video input signal type, digital or analog
(15H) The maximum width of the landscape image
(16H) Maximum width of vertical image
(17H) A version of gamma is displayed, such as 2.20
(18H) DPMS and supported properties, such as the display type is RGB
(19h-22h) Chroma information
(23H) supported basic timing table 1, such as [email protected] (IBM,VGA), [email protected] (VESA)
(24H) supported basic timing table 2, such as [email protected] (VESA)
(25H) Timing information reserved by the manufacturer
Standard timing table supported by (26H-35H)
(36h-47h) Timing Details Description 1, this segment is a more detailed description of a timing, such as landscape, vertical image size, whether the refresh mode is interlaced or progressive, etc.
(48h-59h) Timing Details Description 2
(5AH-6BH) Timing Details Description 3
(6CH-7DH) Timing Details Description 4, these four paragraphs to describe the different timing details, description 1 must have, others can be empty
(7EH) Expansion of the EDID flag bit, if 0 there is no extension edid, if 1 then there is an extended EDID segment
(7FH) CheckSum
The extended EDID consists mainly of several parts:
1. Image and sound modes, such as analog or digital,
2. Color mode, such as YCbCr (4:4:4), YCbCr (4:2:2)
3. A brief description of the timing, which specifies some timing information that is not described in paragraph 1. such as [email protected] 4:3, etc.
4. A short description of the sound, such as PCM (2 channel, 32khz,44.1hz,48hz,16bit,20bit,24bit)
Ac-3,dolby digital+ (6 channel, 32khz,44.1khz,48khz, max bit rate 640kbps)
Speaker (left and right channel)
5.VSDB: Manufacturer's special information, including CEC Physical address, 3D information, deep color information, etc.
6.CheckSum


Two. Checksum calculation method
The checksum is calculated as the first 127 bytes and 0, so for example the checksum=256-(byte0+byte1+...+byt127)%256


Three. Vsdb detailed
Vsdb is a hard-to-understand block in Edid, and the usual EDID editing tool does not provide the option to edit the block, but now usually the edid inside the TV has this information.
is the basic structure of this vsdb.


(00H) The latter 5 bits of this byte represent the length of the vsdb, but do not include itself. This length must be greater than or equal to 5.
(01h-03h) 24-bit identifier, must be equal to 0X000C03
(04h-05h) These two bytes mark the CEC physical address of this HDMI port, such as 1 port is 0x1000,2 port is 0x2000
(06H) BIT7 support_ai flag bit, if 1 indicates that the device supports ACP,ISRC1,ISRC2, it should be set to 0 if not supported
The BIT3~BIT6 flag supports deep color mode and which modes are supported. For example, dc_36bit indicates that each pixel of the output is represented by a 36-bit color, which has a higher precision. If the dc_ycbcr444 is set to 1, then the other 3 items must also be 1
Whether the BIT0 flag supports DVI dual link mode.
(07H): Max_tmds_clock, which indicates the maximum TMDS rate supported, equals Max_tmds_clock*5mhz. If the supported ratio is greater than 165M, or supports deep color, or supports DVI DUAL link then this byte cannot be 0
(08H) bit6,bit7 image and sound delay flag, if 1, then (09H~12H) respectively marked progressive, interlaced image, sound delay information. If it is 0, there is no such message.
BIT5: Additional HDMI image format, that is, in addition to the previously defined timing, other supported formats.
Consists of 4 parts
1 bytes 3d_present Indicates whether to support the three-dimensional information
1 bytes Indicates the length of additional image format information and 3D format information
The third section details the support for those additional HDMI formats, and the Part IV supports which 3D formats

HDMI EDID Interpretation