Internal Video Clock
That is the default genlock setting and will use the SDI output. It means "run at precisely the clock rate that the SDI output needs.
Internal GPU clock
GPU Clock uses the GPU to clock the output, and the expected use of this setting, for instance, if you are using a projector of the GPU output. That means the switcher runs at precisely the GPU clock rate. If you are using the GPU clock to control the output, you might drop frames on SDI audio and video because now the frames are running at the rate needed for the GPU and not the SDI out.
Genlock to External Video Clock (SDI)
This feature allows the TriCaster to lock its SDI video output, to timing derived from an external analog reference signal (house sync, such as “black burst”), that is connected via the Genlock BNC connector on the back of the unit. The term (SDI) is referring to any of the physical video IO ports on the unit.
When an external analog reference signal is connected, the default “Reference Type” in the Genlock settings group is SD (Bi-level). However, if you supply an HD reference signal to the Genlock input, you may want to change the setting to HD (Tri-level).
Genlock to External NDI Source
Using an incoming NDI source as the clock, allows the system to be locked to the remote NDI source. If you are using the NDI clock to control the output, most likely, there will be dropped frames on SDI audio and video because now the frames are running at the rate needed for the NDI source and not the SDI out.
*Current as of 3/13/23