If you cannot use a dummy plug, you can use a software trick (though less reliable).
How to Fix the vMix D3D Startup Error: A Complete Guide Starting up your live stream only to be met with a D3DERR_INVALIDCALL vmix d3d startup error
Many D3D errors are caused by third-party applications that "hook" into your graphics card, interfering with vMix's access. If you cannot use a dummy plug, you
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