Apple Compressor 3 - Manual (Page 217)

Approximate duration for 4.7 GB DVD Average bit rate 1
82 minutes 6.0 Mbps
68 minutes 7.5 Mbps
65 minutes 8.0 Mbps
1 For a DVD clip with video, audio, and subpictures: assumes 1.5 Mbps for audio (two-channel AIFF).
Note: When “One pass VBR or “One pass VBR Best” is chosen for very short clips (less than
a minute or two in length), the resulting MPEG-2 output file size may not accurately reflect
the average bit rate you specified. If the MPEG-2 output media file is larger than you want,
you can try transcoding it again at a lower average bit rate.
Stage 3: Choosing GOP Settings
Select a suitable GOP structure and size and decide whether you want the GOPs to be
open or closed.
Note: These settings are not adjustable if you chose an HD video format in the Video
Format tab.
To open the GOP tab and choose GOP settings
1 Click the GOP button in the MPEG-2 Encoder pane to open the GOP tab.
Choose a GOP structure
to control how many
B-frames are used.
Choose open or
closed GOPs.
Choose a GOP size.
2 Choose a GOP structure from the GOP Structure pop-up menu.
For the majority of MPEG-2 encoding jobs for DVD authoring, choose the IBBP GOP
structure.
3 Choose a GOP size from the GOP Size pop-up menu.
For the majority of MPEG-2 encoding jobs for DVD authoring, choose GOP size 15 for
NTSC and GOP size 12 for PAL and 24p.
The options available in this menu are determined by the GOP structure you choose and
by whether or not the GOP is open or closed.
217 Chapter 18 Creating MPEG-2 Output Files