4.1.2

Chapter 5 Advanced tasks 71
Note: Frame rate conversion can have a subtle or dramatic eect depending on how big a
dierence there is between the original and new frame rates, and also depending on the specic
nature of the footage being converted. Footage with a lot of movement yields a much more
visible change than footage with little movement in the frame. Frame rate conversion may also
add visible artifacts in the transcoded le; from stuttering (sometimes called “juddery”) playback,
to repeated frames, ghost images, or other unnatural-looking elements. These eects can be
somewhat mitigated by adjusting the “Retiming quality” property in the Quality section of the
Video inspector.
3 Select a value from the “Field order” pop-up menu to choose a progressive or interlaced frame rate.
If the current setting does not allow eld order modication, this control remains dimmed.
If you want to convert a le with an interlaced format into a progressive format, see About
deinterlacing on page 71.
Note: The properties in the Retiming section of the General inspector are always aected by the
“Frame rate” property, as well as the “Retiming quality” property in the Video inspector.
About deinterlacing
Video to be played on traditional NTSC or PAL televisions is encoded using an interlaced frame
rate. Each frame is actually made up of two half-frames called elds. Each eld contains half the
frame lines; the odd (or upper) eld contains lines 1, 3, 5, 7, 9 and so on, and the even (or lower)
eld contains lines 2, 4, 6, 8, 10, and so on. When the video is played back, the TV displays the
elds in an alternating pattern, which creates an eective illusion of smooth movement. Viewing
interlaced video on a computer screen that displays both elds simultaneously may reveal a
combing eect.
Interlacing creates
a “comb” effect
when viewed on
a computer screen.
You can deinterlace, or remove the elds from an interlaced video clip, by converting it to a
progressive frame rate. The video settings provided in Compressor contain a “Field order” pop-up
menu in the Video inspector that you can use to turn interlacing on or o for the transcoded
le. For more information, see the topic that covers the format you’re using for transcoding, for
example, QuickTime Movie on page 46 or MPEG-2 on page 37.
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