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KB01632 - Understanding EDID Challenges and How to Resolve Them


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Summary: Understanding EDID Challenges and How to Resolve Them

This article is a review of common audio and video challenges which can be resolved with EDID management. 





Extended Display Identification Data (EDID) is sent from sink devices, such as displays, to source devices. EDID tells a source which audio and video formats and display modes are supported by your display or other sink device.




No Audio EDID, No Audio


This is often seen with projectors. If your projector doesn't have built-in speakers or audio output, it may not ask the source to send a supported audio format. The default configuration of some Atlona products is to repeat the EDID sent by your display. In this case, you may not have audio output.


EDID_projector.svgEDID does not contain supported audio information so the source will not send an audio signal to de-embed.


If you are de-embedding audio for ceiling speakers in a conference room with a projector, EDID management is required to ensure audio is sent by the source. Set a 2CH audio EDID in your Atlona equipment settings. This will tell your sources to send audio that your equipment can de-embed.

Most Atlona switchers, matrices, distribution amplifiers, and scalers provide EDID management. Please refer to your product manual for EDID management settings.

 EDID_projector_managed.svgThe matrix switcher (center) is managing EDID—2CH PCM audio is being requested. The source now sends an audio signal.


Unsupported Display Mode in EDID, No Video


If you have equipment in your signal path which does not support a display mode or refresh rate requested by your display, video pass-through may fail. This will occur if you have an HDR source, an HDR sink, but the signal is passing through equipment which will not support HDR.


EDID_HDR_EX.svgDisplay is asking for an HDR signal.


In this case, the UHD-EX-70-2PS extender kit does not support HDR10 at 60 Hz (only 24 Hz is supported). The UHD-EX-70-2PS also does not manage EDID so this extender kit will pass along the EDID requesting a 60 Hz HDR signal, but once the source starts sending the 60 Hz signal, the extender will not pass the video signal.


EDID_HDR_EX_video.svgSource sends the 60 Hz HDR the display asked for, but this extender does not support HDR at 60 Hz. No video signal passes.


You may observe the same behavior with resolutions, chroma subsampling, and other video signal characteristics which are unsupported by devices in your signal chain. You must either manage EDID so that no sources send signals your devices cannot handle, or spec all of your devices to match the highest performance video source. Read the specifications of your equipment carefully to ensure compatibility.


 Color Space Mismatches


Color spaces are maps for colors which are shown when coordinates for each color are received by a display. There are different color spaces, commonly RGB and YCbCr or YUV. If your source is providing coordinates for one space and your display is applying them to the wrong map, you will see strange coloration—a color space mismatch.

 BlueMarbleRGB.jpgLeft: Original image; Center: RGB coordinates in a YCbCr space; Right: YCbCr coordinates in an RGB space


Color space issues may occur if EDID is not properly managed.

  • Older and analog equipment may be RGB only and unable to convert to or from the YCbCr color space used for digital video. In these cases, the source may not receive an EDID and will not know to send RGB. So you will either need a source device which supports manual selection of color spaces or you will need to use an RGB EDID.


  • Converting from HDMI to DVI can also cause color space issues. DVI is RGB only. HDMI supports YCbCr and RGB. In these cases, you may be able to use an Atlona DVI EDID for your source. If your Atlona equipment has an EDID management feature, DVI EDIDs may be provided. These EDIDs may also work with older RGB projectors. Your Atlona product manual should contain a list of the included EDIDs.


  • You may also see a color space issue if your sink device is sending an EDID that your source does not understand or is not sending any EDID. In that case, the source will send a default video signal which the sink may display incorrectly. This can also occur if you have a damaged HDMI cable or failed HDMI handshake and EDID data is not sent.


Article ID: KB01632

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