EDID and capabilities

Data block

CEA extension blocks inside an EDID

An EDID is not one description but a stack of small ones. Knowing which data block holds which capability tells you exactly which Diva flag to reach for.

An EDID begins as 128 bytes in a fixed layout describing the display in the terms of 1994. Everything a modern television needs to say lives in the extension blocks that follow, and the one HDMI uses is the CEA extension. Inside it, capabilities are listed as data blocks: each is a run of bytes preceded by a tag saying what kind of information it holds and how long it is.

The common ones are the video data block, holding the short video descriptors that list supported resolutions and frame rates; the audio data block, a list of short audio descriptors of three bytes each, one per format; speaker allocation; the colorimetry data block, which is where BT.2020 support is declared; the HDR static metadata data block, naming which transfer functions the display accepts, such as SDR gamma, PQ and HLG; the HDR dynamic metadata data block, which is where HDR10+ support is declared; and vendor specific data blocks, each identified by an IEEE registration number, one for HDMI itself, one for HDMI Forum features and one that Dolby uses for Dolby Vision.

Every extension block is 128 bytes and no more. That is why a display with a long resolution list, every audio format and a Dolby Vision block can run out of room, and why editing an EDID by hand is often a matter of taking something out before you can put something in.

How the HDfury Diva edits data blocks

You rarely touch bytes on the Diva. In AUTOMIX mode it builds an EDID from the real capabilities of the connected sinks, and the fourteen forceable flags then each reach into one block: HDR 10+, HLG and 2020/xvYCC touch the HDR and colorimetry blocks, 2.0 Stereo, 5.1 Multi and 7.1 Full rewrite the short audio descriptors, no YCbCr and no 3D take capabilities away, and DV Force Metadata, DV Remove and DV Limit 300MHz act on the Dolby Vision block.

Whether a flag adds or removes is fixed, and the control commands say so plainly. Set edid hdr10 on, set edid hlg on and set edid bt2020 on only add the capability if it is missing; they will not remove it if the sink already declares it. Removal has its own commands: set edid dvremove on, set edid 3dremove on and set edid yuvremove on.

Reading blocks and moving them around

In CUSTOM mode you pick a whole ready-made set instead. Banks 11 to 100 follow a strict pattern of a video format, a colour and HDR variant, then one of three audio levels, All Sound, SPDIF or Stereo, so choosing a table is choosing which blocks the source will read. DOWNLOAD ACTIVE EDID TABLES saves the EDID of any input or output as a file, and UPLOAD EDID TABLES with SEND EDID loads one into custom banks 8, 9 or 10, which ship empty.

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