Looking Glass

Looking Glass is an open source application that allows the use of a KVM (Kernel-based Virtual Machine) configured for VGA PCI Pass-through without an attached physical monitor, keyboard or mouse. This is the final step required to move away from dual booting with other operating systems for legacy programs that require high performance graphics.

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Performance & Latency

Looking Glass is targeted at extremely low latency use requirements on the local computer, it is not designed to stream over a network or pipe but rather through a block of shared memory. In current testing at a refresh rate of 60Hz it is possible to obtain equal or better then 16 milliseconds of latency with the guest. If the user doesn't care for VSYNC this can be further reduced to under a few milliseconds on average.

Figure 1: Low Latency Demonstration


Unlike network based streaming applications, Looking Glass does not use any form of compression or color space conversion, all frames are transferred to the viewer (client application) in 32-bit RGBA without any transformations or modifications. This is possible through the use of a shared memory segment which enables extremely high throughput low latency guest to host communication.

Figure 2: Colors appear accurately on screen.


Host Requirements

Anything recent graphics device that supports OpenGL should do fine, the client application does not perform any heavy graphical work.

Guest Requirements

At this time only Windows 10 is supported with any video card supporting DXGI Desktop Duplication or the NVIDIA Capture API (Professional cards only such as Quadro).


Looking Glass has been released under the GPL 2.0 license by Geoffrey McRae of HostFission