Grass Valley PROFILE FAMILY v.2.5 - Manual (Page 171)

Selecting Vertical Blanking Interval Storage Lines
Profile Family 171
Figure 82. Edit Compression Presets dialog box
Selecting Vertical Blanking Interval Storage Lines
The MPEG section of the Edit compression presets dialog box has a button
labeled
VBI lines (see Figure 82). This button opens the Vertical Blanking
Interval Storage dialog box (see Figure 83) which allows you to select from one
to three lines in the vertical blanking interval (VBI) that will not be compressed
with the video data, but will be stored without being encoded to avoid losses.
This is desirable for uses such as closed captioning which would be seriously
degraded by losses incurred at lower bit rates.
The Compress VBI checkbox at the top forces all the lines in the VBI to be
compressed. The other checkboxes allow you to select up to three of the
Luminance or Chrominance lines.