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145
Adobe Premiere Pro Help
Editing a Sequence
Using Help
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145
Processing interlaced video fields
In most video, each frame consists of two
fields
. One field contains the odd-numbered
lines in the frame, and the other contains the even-numbered lines. The fields are
inter-
laced
, or combined, to create the complete image.
Ordinarily, interlace isn’t apparent to a viewer. But because each field captures the subject
at a slightly different moment in time, playing a clip in slow-motion, creating a freeze
frame, or exporting a frame as a still image makes the two fields discernible. In these
circumstances, it’s usually preferable to
deinterlace
the image—that is, eliminate one field
and create the missing field either by duplicating or interpolating the lines of the
remaining field.
Another unwanted effect can arise from inadvertently reversing the
field dominance
, or
the order in which the fields are recorded and displayed. When the field dominance is
reversed, motion appears jerky because the fields no longer appear chronologically. Fields
can become reversed in the following situations:
•
The field dominance of the original videotape was the opposite of the field dominance
of the video-capture card used to capture the clip.
•
The field dominance of the original videotape was the opposite of the field dominance
of the video-editing or animation software that last rendered the clip.
•
You have set an interlaced clip to play backward.
You can process fields for an interlaced clip in the sequence so that the clip’s picture and
motion quality are preserved in situations such as changing the clip speed, exporting a
filmstrip, playing a clip backward, or freezing a video frame.
To specify field processing options for a clip:
1
Select a clip in the Timeline window, and choose Clip > Video Options > Field Options.
2
Select Reverse Field Dominance to change the order in which the clip’s fields appear.
This option is useful when the field dominance of the clip doesn’t match your equipment
or when you play a clip backward.
3
For Processing Options, select one of the following choices:
None
Doesn’t process the clip’s fields.
Interlace Consecutive Frames
Converts pairs of consecutive progressive-scan (noninter-
laced) frames into interlaced fields. This option is useful for converting 60-fps progressive-
scan animations into 30-fps interlaced video, because many animation applications don’t
create interlaced frames.
Always Deinterlace
Converts interlaced fields into whole progressive-scan frames.
Adobe Premiere Pro deinterlaces by discarding one field and interpolating a new field
based on the lines of the remaining field. It keeps the field specified in the Field Settings
option in the Project Settings (see
“Specifying project settings” on page 58
). If you
specified No Fields, Adobe Premiere Pro keeps the upper field unless you selected Reverse
Field Dominance, in which case it keeps the lower field. This option is useful when freezing
a frame in the clip.
Flicker Removal
Prevents thin horizontal details in an image from flickering by slightly
blurring the two fields together. An object as thin as one scan line flickers because it can
appear only in every other field.
