Controlling what an NVR is displaying

Hello, Is there a make of NVR on the market that allows a network connected PC control what the NVR is currently displaying? e.g. via an API
I plan to connect the HDMI port on the NVR to an HDMI modulator and then have the NVR display as an extra TV channel. I've already got a remote control next to the TV that talks to a program on a PC. Would be good if I could use the remote to select the display from specific cameras on the NVRs TV channel. Thanks. Nicholas