User Guide

ADOBE PREMIERE PRO 2.0
User Guide
391
Note: When comparing CBR and VBR files of the same content and file size, you can make the following generalizations:
A CBR file may play back more reliably over a wider range of systems, because a fixed data rate is less demanding on a
media player and computer processor. However, a VBR file tends to have a higher image quality, because VBR tailors
the amount of compression to the image content.
Bitrate Specifies the number of megabits per second of playback for the encoded file. (This is available only if you
select CBR as the Bitrate Encoding option.)
The following options appear only if you select VBR as the Bitrate Encoding option:
Encoding Passes Specifies the number of times the encoder will analyze the clip before encoding. Multiple passes
increases the time it takes to encode the file, but generally results in more efficient compression and higher image
quality. (Adobe After Effects does not support multiple encoding passes.)
Target Bitrate Specifies the number of megabits per second of playback for the encoded file.
Maximum Bitrate Specifies the maximum number of megabits per second of playback you want the encoder to
allow.
Minimum Bitrate Specifiestheminimumnumberofmegabitspersecondofplaybackyouwanttheencodertoallow.
The minimum bitrate differs according to the format. For MPEG-2-DVD, the minimum bitrate must be at least 1.5
Mbps.
M frames Specifies the number of B frames (Bi-directional frames) between consecutive I frames (Intra-frames) and
P frames (Predicted frames).
N frames Specifies the number of frames between I frames (Intra-frames). This value must be a multiple of the M
frames value.
Closed GOP Every Specifies the frequency of each Closed Group of Pictures (Closed GOP), which cannot reference
frames outside of the closed GOP. A GOP consists of a sequence of I, B, and P frames. (This option is available when
you choose MPEG-1 or MPEG-2 as the format.)
Automatic GOP Placement When selected, sets the placement of Group of Pictures (GOP) automatically. (This
option is available when you choose MPEG-1 as the format.)
Note: MPEG-1 and MPEG-2 formats include numerous advanced options not listed here. In most cases, selecting a
format or preset designed for your target output sets the appropriate options automatically. For detailed information on
options not listed, consult the specifications for the MPEG-1 (ISO/IEC 11172) and MPEG-2 (ISO/IEC 13818) formats.
MPEG multiplexer preset options
Multiplexer preset options control how After Effects and Adobe Premiere Pro merge MPEG video and audio data
into a single stream. The exact options available depend on the MPEG format you choose.
When you choose the MPEG-2 format, all Multiplexer options provided by the MPEG standard are available for
manual control. In most cases, it’s better to select an MPEG format specifically targeted to your output medium (such
as MPEG-2 DVD).
For more information on the options available, search the web for the ISO/IEC standards for the MPEG formats.
MPEG format ISO/IEC standard
MPEG-4 ISO/IEC 14496
MPEG-2 ISO/IEC 13818
MPEG-1 ISO/IEC 11172