VSync with NVIFR

I’m building some low latency remote desktop software that captures applications. As soon as the front buffer is updated, I’d like to begin a capture of that frame. Is there a way to do this?

From what I can tell, there isn’t a way to get any info about when the front buffer has changed. Right now, I just call nvIFROGLTransferFramebufferToHwEnc at some random time, which might be many ms since the front buffer has swapped.

The docs mention nvIFROGLTransferFramebufferToHwEnc is asynchronous. I was hoping this might mean that the capturing would wait until the next front buffer was swapped, and then do a capture, but from testing this doesn’t seem to be the case.

Is there something I’m missing, or some information I could use to tell when the front buffer has changed?