Likewise, the V bit is used to indicate the start of the vertical blanking region; an EAV packet with V = 1 indicates the following line ( lines are deemed to start at EAV ) is part of the vertical interval, an EAV packet with V = 0 indicates the following line is part of the active picture.
32.
VIR ( or Vertical interval reference ), widely adopted in the 1980s, attempts to correct some of the color problems with NTSC video by adding studio-inserted reference data for luminance and chrominance levels on line 19 . Suitably equipped television sets could then employ these data in order to adjust the display to a closer match of the original studio image.
