User Manual

Vertical Blanking Information
1086
For example, with a ratio of 24 film frames to 30 video frames, a 7-frame video edit corresponds
to approximately 5.6 film frames. However, film cuts cannot include partial frames, so the edit
must be rounded to 5 or 6 frames.
To make these adjustments, the following occurs during matchback:
• If the total video-sequence duration at the end of each cut is a frame longer than the film, the
system subtracts a frame from the last video edit. If the video is a frame too short, a frame is
added to the last video edit.
• Where an essential frame was added to or subtracted from the beginning or end of each edit,
the system adds matchback information to the cut list, stating that matchback shortened or
lengthened the tail of the clip by one frame. The assistant editor or negative cutter can use
this information to check the edit.
• Each track in the sequence must be corrected independently because the start and end points
for split edits are different for each track. As a result, the picture and audio for a matchback
video edit might be out of sync by no more than one frame.
Matchback Limitations
Matchback is subject to the following limitations:
• The Matchback option uses key numbers to conform the negative, so you must have
key-number information entered into the bins for the project.
• You can generate cut lists but not change lists in a matchback project.
• The matchback information applies to the picture only. You must generate a separate list (an
EDL, for instance) for conforming the audio source tapes.
• Be sure to remove unwanted match frames (add edits) from your sequence before generating
the cut list. Otherwise, the calculation of matchback frames will include these edits. For
information about removing match-frame edits, see “Working with Add Edits (Match
Frames)” on page 723.
Vertical Blanking Information
Avid editing applications using Avid input/output hardware let you work with vertical blanking
information in some SD material. You can choose whether to display 5 lines above each field in
NTSC and 8 lines above each field for PAL and whether to preserve the lines when you perform
a digital cut. These lines can be used to store additional encoded information such as closed
captioning, edgecodes or key numbers for film projects, or various interactive or enhanced TV
codes. This section describes when it is useful to preserve the information and describes the
limitations involved when preserving these lines.