DigiDesign Digidesign Pro Tools 8.0, Справочное руководство

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Chapter 43: Mixdown 965
MPEG-1 Layer 3 (MP3)
The MPEG-1 Layer 3 compression format (MP3)
is used for streaming and downloading audio
over the Internet, and for playback on portable
devices. The MP3 Export Option is required to
use this file type.
When you select this format, the Resolution pop-
up menu in the Pro Tools Output Options dia-
log is unavailable. The resolution is set by the
encoder.
The sample rate chosen is given to the codec as
a base sample rate for operations. The actual
sample rate of the resulting file is determined in
the MP3 Encoder Options dialog. For example, if
a base sample rate of 48000 Hz is chosen, the
MP3 Encoder Options dialog will allow output
streams in 48, 24, or 12 kHz, depending on en-
coding quality.
When you export or bounce to MP3 format, you
can set the following options:
Encoder Settings
Encoder Speed
Determines the audio quality of
the bounced file. There are two options:
Highest
Quality
and
Fastest Encoding Time
.
The
Highest Quality
option can take up to five
times longer to process audio than the
Fastest
Encoding option, so you should use it only when
the highest fidelity is essential and you have the
time to devote to the encoding process.
Constant Bit Rate (CBR) Encodes the file at a
single bit rate that you choose from the
Constant
Bit Rate (CBR)
pop-up menu. Because the bit rate
is fixed, the quality of the encoded audio will
vary depending on the nature of the material be-
ing compressed. The
128 kbit/s
option is gener-
ally best for streaming over the Internet, since it
has predictable bandwidth requirements.
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.
The MP3 Export Option is available for pur-
chase from the online DigiStore at the Digi-
design website (www.digidesign.com).
MP3 Export Options