Apple Compressor 2 - Manual (Page 220)

220 Chapter 16 Using the Preview Window
Adding Markers to a Clip
MPEG-1 and MPEG-2 GOP patterns automatically insert I-frames on whatever basis the
pattern dictates. The Preview window offers additional MPEG-1 and MPEG-2 flexibility
by allowing you to manually insert compression markers into your source media file
wherever you decide additional I-frames are needed, regardless of your chosen GOP
pattern and size. These are known as forced I-frames, and are useful if you want to mark
a major scene change or some other major change in the source media file so that you
can improve the quality of the MPEG-1 or MPEG-2 file. See “
Understanding GOPs and
Frame Types ” on page 140 for more information on I-frames.
In addition, adding compression markers to your clip allows you to create chapter
markers that DVD Studio Pro can understand and use. See “
Adding DVD Studio Pro
Chapter Markers to a Clip ” on page 222 for more information.
These manual settings are also preserved when you transfer a media file directly from
Compressor to another application such as DVD Studio Pro.
Note: I-frames should not be added to anything but MPEG-1 or MPEG-2 output media
files. The MPEG-1 format does not support chapter markers.
To add a compression marker to your clip:
1 Open the Preview window.
2 Select the “Show Chapter Markers” and “Show Compression Markers” items from the
Marker pop-up menu.
3 Choose a clip from the Batch Item pop-up menu or click the Batch Item selection
button until the clip you want appears in the pop-up menu.
Note: Clips that already contain markers, such as those from Final Cut Pro, will show
those markers in the timeline. You can edit those markers the same as if you had
manually entered them.
4 Make sure that the selected setting is using an MPEG-1 or MPEG-2 output format. (You
cannot force keyframes with the H.264 for HD DVD file format.)