Apple Compressor 2 - Manual (Page 137)

Chapter 10 Creating MPEG-2 Output Files 137
For more information on the Apple Qmaster distributed processing system, see the
Distributed Processing Setup guide.
 Average Bit Rate slider and field: Choose an average bit rate between 2 Mbps and
9 Mbps for standard definition (SD) video, or between10 and 29 Mbps for high
definition (HD) video. You can also enter any number in these ranges into the
accompanying field.
 Maximum Bit Rate slider and field: Choose a maximum bit rate between 5 Mbps and
9 Mbps for standard definition (SD) video, or between 12 and 29 Mbps for high
definition (HD) video. You can also enter any number within these ranges into the
accompanying fields. This slider is only available with the VBR modes and cannot be
set lower than the average bit rate.
Important: When determining average and maximum bit rates for standard DVD
playback, remember to consider the bit rate of your audio track as well as the
MPEG 2 bit rate. You must keep the total of both average and maximum audio and
video bit rates under 10.08 Mbps, the maximum guaranteed transfer rate from
standard DVD players. (Because DVD-compatible audio formats are constant bit rate
(CBR), there is no maximum audio bit rate to worry about.) For example, if you are
using AIFF audio at 1.5 Mbps, you should keep both the average and maximum video
bit rates under 8.5 Mbps. Typically, your average bit rate will be lower than this (for
example, 3.5 Mbps for 2 hours of footage on your DVD). However, your maximum bit
rate must also stay under this number. 8.0 Mbps maximum bit rate is recommended
to provide an extra margin for error (for example, to accommodate subtitle streams).
If you are using one of the DVD-compatible compressed audio formats such as Dolby
Digital or MPEG-1/Layer-2, your audio bit rate may be as low as 0.2 to 0.4 Mbps, in
which case you can set your maximum bit rate about 1 Mbps higher. As a general
rule, set your maximum bit rate at least 1 Mbps higher than your average bit rate, to
allow for bit rate variability in achieving the goal of constant quality.
 Motion Estimation pop-up menu: This menu is another trade-off between image
quality and processing time, especially if there is a lot of motion in the source file.
Choose one of the following settings:
 Good: The fastest ME setting. This mode does well even with significant amounts
of motion between frames, if the motion has minimal interfield motion within
frames. For example, footage that has been exposed to frame-rate conversion or
other effects processes tends to have little interfield motion. In general, use Good
with the one pass encoding mode.