Specifications

Chapter 29: Mixdown 487
• Constant Bit Rate (CBR) encodes the file at a
single bit rate that you choose from the CBR
pop-up menu. Because the bit rate is fixed, the
quality of the encoded audio will vary de-
pending on the nature of the material being
compressed. This option is best for streaming
over the Internet, since it has predictable
bandwidth requirements.
•Variable Bit Rate (VBR) encodes the file at a
varying bit rate to maintain the level of en-
coding quality that you choose from the VBR
pop-up menu. The bit rate varies automati-
cally depending on the nature of the material
being compressed. This option is best for per-
sonal jukebox applications.
ID3 Tag Info Settings
ID3 Tag Type The ID3 tag stores data about the
encoded audio file that is used by MP3 players to
display information about the file. Pro Tools
supports three versions of this tag, in order to
provide backward compatibility with older MP3
players:
• ID3 v1.0: Appears at the end of a streaming
MP3 file, so that tag information is only dis-
played after software streaming is finished.
• ID3 v1.1: Same as version 1.0, but adds track
number information to the tag.
• ID3 v2.3: Appears at the front of a streaming
MP3 file, so that tag information is displayed
when streaming begins.
Title/Artist/Album/Comment Type the title, art-
ist, and other information for the MP3 file. This
information is displayed by many MP3 players.
Genre Choose a genre for the file. This informa-
tion is displayed by many MP3 players, and can
appear in searchable catalogs and databases.
Track Number If you select ID3 tag type v1.1 or
v2.3, you can enter a CD track number for the
file. This information is displayed by many MP3
players.
Year Enter a year for the file. This information is
displayed by many MP3 players.
Advanced Settings
The options listed under Advanced Settings, un-
der normal situations, do not need to be
changed from their default values.
Pad To Match Bit Rate Exactly This option de-
termines whether MP3 frames are padded to
maintain bit rate very precisely. You should
only select this option if you need a file with an
exact bit rate, for specific applications (such as
synchronous transmission over an ISDN line).
Allow Intensity Stereo Coding This option deter-
mines whether the encoder takes into account
the frequency of a signal when encoding its
phase characteristics, allowing for more com-
pression at low bit rates. In most cases, you
should leave this option selected. However, if
you are working with highly phase-dependent
material, such as Dolby Surround, you may
want to deselect this option.
While ID3 v2.3 is becoming the standard
MP3 format, not all MP3 players currently
support ID3 v2.3. Contact the developer of
your player software for compatibility infor-
mation.
Padding of MP3 frames can cause problems
with some versions of Internet streaming
software. If your files are destined for desk-
top or Internet delivery, do not select this
option.