Apple Compressor 3 - Manual (Page 213)

About 24p (23.98p)
For DVD authoring and encoding, 24p refers to a video sequence that contains 24
progressive (non-interlaced) frames per second, with NTSC-related standard definition
frame dimensions (720 x 480 for MPEG-2). Film-based movies have a native frame rate of
24 fps, and because the MPEG-2 format is able to represent 24 fps video internally, many
commercial movie DVDs are encoded in this way. But any time you use NTSC video in
your project, the frame rate of film-transferred material will be slowed down from 24 fps
to 23.976 fps (rounded to 23.98) and a 2:3:2:3 pull-down is added. So, the more accurate
term is actually 23.98p.
Compressor can also do this for 24p source video files. For such material, the 23.98 frame
rate option (in the Video Format tab) compresses each source frame one-for-one, without
compressing repeated frames or fields in order to achieve a 29.97 fps display rate. This
results in higher quality at a lower compressed bit rate than would be possible if the 24p
material were converted to 29.97 fps prior to transcoding. Compressor also sets internal
MPEG-2 frame flags correctly, so DVD players will properly apply the 3:2 pull-down process
for display on 29.97 fps interlaced NTSC TV sets.
Note: If your source video has a frame rate of 24.00 fps rather than 23.98 fps, Compressor
skips one out of every 1000 source frames. If the 24p source video is 23.98 fps, Compressor
transcodes all source frames, without skipping (or repeating) any of them.
MPEG-2 Transcoding Workflow
This section includes step-by-step instructions for setting your MPEG-2 attributes prior
to creating MPEG-2 output files with Compressor. Make your MPEG-2 settings from the
MPEG-2 Encoder pane by either modifying an existing setting or creating a new one in
the Settings tab.
See the following steps for working with the MPEG-2 output file format. For example
values for each of these settings, see
Example MPEG-2 Settings .
• Stage 1: Choosing Video Format Settings
• Stage 2: Choosing Quality Settings
• Stage 3: Choosing GOP Settings
• Stage 4: Choosing Extras Settings
Stage 1: Choosing Video Format Settings
It’s important to match the video format, aspect ratio, and field dominance to those of
your source media file. See
Video Format Tab for a more detailed description of each of
these settings.
213 Chapter 18 Creating MPEG-2 Output Files