Isadora offers integrated Spout video-sharing actors as well as support for the previously supported Spout FFGL plugins on Windows.
Using Spout to share video directly from the GPU to external applications is a very useful and high-performance feature.

Due to its high-performance nature, there is a common problem that many users run into when setting up Spout for use on their Windows machines (most often laptops).
The problem is due to a power-saving feature included with many systems, that uses the Intel integrated video that is included on Intel CPUs.
What happens is the system will switch between using the dedicated high-performance video card and the energy-saving, low-performance Intel video card dynamically to save on power consumption.

This switching can cause several OpenGL problems so it is recommended to ensure that Isadora.exe is set to use only the high-performance graphics card.

How to set Isadora to use the high-performance graphics card

This article shows the different screens within the Nvidia control panel:

The article shows a section: 3D settings / manage 3D settings / Program settings (tab)

Both AMD and nVidia offer similar approaches to managing their respective power-saving features, so if you have an AMD card you will need to find a similar dialogue.

That section will allow you to select isadora.exe from the 'Program Files (x86)' folder in your system drive (probably C:) and set isadora.exe to only use the dedicated video cards.

NOTE: It is also important to set any other application either sending or receiving Spout video to use only the dedicated video card. This includes 3rd party applications as well as programming tools like Processing or Max MSP.