Some older video applications may depend on DirectX 9 overlays to work correctly. In Windows 8.1, there are rare scenarios in which the DirectX 9 overlay hardware is not available. In these situations, video playback doesn't work.
In Windows 10, those scenarios are still rare, but they may occur more frequently than in Windows 8.1. This is especially true when your display options are set to a lower resolution than the native screen resolution.
In Windows 10, those scenarios are still rare, but they may occur more frequently than in Windows 8.1. This is especially true when your display options are set to a lower resolution than the native screen resolution.