Hey ,
So after doing some more fiddling with the materials and trying to understand what it is that is actually affecting the change, I was able to confirm it was the post processing that was causing the distortion. If you type ‘showFlag.PostProcessing 0’ into the command console you can see the visual change of your material. There are a few workarounds to fix this issue.
The first one, and more explicit example, would be to add another post process volume with its bounds within the range of the viewer watching the video in the game to effectively nulify, or reverse, the global post processing.
The second suggestion would be to set up a new material using a Multiply and a Power node. Connect constant vectors to these nodes and convert them into Parameters. One parameter value will control the Brightness, and the other will control the Contrast. Apply this material to your object, and toggle between Unlit and Lit mode, adjusting the material until you get them to match. This will not be perfect, but will get you close to you desired outcome.
Media Material Parameters
Cheers,