Definitions for "Vertical blanking interval"
Keywords:  vbi, caption, ntsc, blanked, sync
A portion of the television signal that does not contain visual data. In NTSC, the VBI are lines 1 through 21 in each field.
The blanking time at the beginning of each field. It contains equalizing pulses and vertical sync pulses.
The interval of time for the scan to return from the end of one frame back to the beginning of the next frame. This is typically measured in scan lines. The NTSC calls for the VBI to be 40 scan lines.