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• The cvt command line program, which is available on Linux, generates modelines in the correct format (though you must remove the quotation marks around the mode name). Use the -r flag, which reduces blanking.

• EDID Information in the BrightAuthor:connected DWS, and the edid hdmi BrightSign command line, both output the Detailed Descriptor Mode (DTD) EDID entries in the modeline format. You can connect a screen, query the EDID, and use the resulting modeline as your custom modeline.

• You can create your own modeline from the documentation for a particular screen.

Custom Mode

Setting videomode to custom means that the stored modeline will be used. The configured mode will always be 8 bits per color and RGB. For modes where the pixel area is greater than 2.5 million, the graphics layer will be a quarter size and upscaled by default. Setting the mode to custom:fullres forces a full resolution graphics layer as with the higher resolution preset modes. Some players don't allow fullres modes - see Full-Resolution Graphics for more information. 

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Use SetCustomModeline() in roVideoMode to parse the modeline, check that it is within the supported range, and then store the value in the registry. The new modeline is only active when the videomode is set to custom and, as with most videomode changes, it requires an application restart. Methods like GetConfiguredMode will return the width, height, and calculated frame rate from the custom mode. See the examples at the bottom of this page.

Enabling Custom Resolutions in JavaScript

The videomodeconfiguration class contains setCustomModeline(), which returns whether or not a restart is required. If the videomode is already set to custom, a restart will be required.

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See https://github.com/brightsign/video-mode-plugin/tree/master for example video-mode plugins for single and multi HDMI HDMI® output models.