I use Decklink SDI and HDMI as external output, but there is a delay impossible to reduce with this kind of Hardware.

This delay doesn't exist with a FULLSCREEN output, but if you move a windows program from screen 1 to screen 2, it appears on it.

With an an EXTERNAL output from the graphic card output, it will be possible to attack directly the graphic card hardware trough Nvidia API for exemple and no windows programs can be superposed.