Apple Logic Pro 9 - Manual (Page 839)

If the PCM option is unselected in the Destination pane, a temporary PCM file is bounced
as a source for encoding to MP3/M4A: AAC or burning to a CD, according to the options
selected in the PCM pane.
Selecting the MP3 option in the Destination pane automatically disables the PCM >
Surround option (following a warning message). This is because the MP3 format does
not support surround. Split Stereo format is, however, possible, even if the encoded MP3
file is set to Joint Stereo mode.
Select the MP3 name (and select its checkbox) in the Destination pane to access the
following options:
• Bit Rate (Mono/Stereo) pop-up menus: MP3 bit rates are available between 32 kbps and
320 kbps, but default to 80 kbps mono, and 160 kbps stereo. These rates offer acceptable
quality and good file compression.
To enhance audio quality, provided you can afford the extra file size, choose:
• 96 kbps for mono streams
• 192 kbps for stereo streams
You can choose higher rates, but the quality improvement afforded by bit rates above
96/192 kbps is nominal.
• Use Variable Bit Rate Encoding (VBR) checkbox: Variable Bit Rate encoding compresses
simpler passages more heavily than passages that are (more) harmonically rich, generally
resulting in better-quality MP3 files.
Unfortunately, not all MP3 players can accurately decode VBR-encoded MP3s, which
is why this option is turned off by default. If you know that your target listeners can
decode VBR-encoded MP3s, you can turn this option on.
839 Chapter 29 Bouncing Your Project