Read Vertical Synchronization

Hello,
can somebody say me, if it is possible to read the vertical synchronization signal with Nios II?

I have some videosignals and each of the signals has his own Framebuffer. Now I want to delay the outputs of the Framebuffers, so that all videosignals can use the same vertical synchronization signal. But for this, I have to read out the v_sync signals.

Thank you