User Manual

Vertical Blanking Information
1089
Editing a Sequence with Vertical Blanking Information
After a sequence is created and output from an Avid editing system, some facilities apply VBI
information to the tape to add information such as closed captioning. Often, the tape is
recaptured so that the sequence can be repurposed for another market. The VBI option in the
Video Output tool lets you display the VBI information and maintain the information when you
output the repurposed sequence.
Your Avid editing application uses the following rules when applying effects to material
containing VBI information:
• Single track effects do not alter the VBI information. For example, if you apply a color
correction effect to the sequence, the VBI lines are not affected.
• Multi-track effects such as picture-in-picture effects or 3D Warp effects use the VBI
information of the track on the lowest layer. (Swap sources is ignored in the VBI area).
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If you apply a multi-track effect such as a 3D Warp effect to a sequence with a single track, the
VBI information will not be visible. One way to work around this problem is to create a second
video track and duplicate that portion of the sequence on the second track. Then apply the 3D
Warp effect to the top track. The VBI information will display on the bottom track.
• Transitions are treated as cuts in the VBI area.
• Timewarp effects copy the VBI of the input’s temporally nearest field. In mild timewarp
effects this may allow VBI to pass through unaltered.
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You cannot add or remove VBI information from a sequence. However, you can use the Blank
option to turn off the VBI display for the entire sequence.
You cannot preserve VBI information for DV resolutions. You can only preserve VBI information
for JFIF, uncompressed, and MPEG IMX resolutions.
Effects of Preserving Vertical Blanking Information on Compressed
Video Quality
For resolutions other than 1:1, preserving vertical blanking information when you capture can
affect the video quality in the rest of the frame. For example, depending on the compression
ratio, a video frame might look more blocky with vertical blanking information included.
Your Avid editing application performs the following operations when capturing a frame:
1. It captures the entire frame (including the 5 or 8 extra lines per field) as an uncompressed
frame.
2. It compresses the frame if compression is selected.