High Quality Content by WIKIPEDIA articles! Vertical synchronization (v-sync, v-synch, vbl-sync, vbl-synch) refers generally to the synchronization of frame changes with the vertical blanking interval. Since CRTs were nearly the only common video display technology prior to the widespread adoption of LCDs, the frame buffers in computer graphics hardware are designed to match the CRT characteristic of drawing images from the top down a line at a time by replacing the data of the previous frame in the buffer with that of the next frame in a similar fashion.