Apple Compressor (4.0) - Manual (Page 82)

Chapter 5 Custom settings and output formats 82
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Compression Preset: Specifies one of the dynamic range processing modes built into the AC-3
format. The default setting of Film Standard Compression should be used only when you’re
encoding an original mix intended for cinema. In almost all cases, you should choose None.
Important: It’s critical that you set Dialog Normalization correctly in the Audio tab if you intend
to use any of these Compression Preset settings. The Compression Preset settings assume that
the audio, after the dialogue has been normalized, is at the normal listening level of 31 dBFS.
Levels that are consistently louder than that result in distorted sound and erratic levels.
Note: If you’re building a Dolby Digital Professional 5.1-channel surround sound DVD, choose
Film Standard Compression.
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General Digital Deemphasis: Specifies whether input audio data is preemphasized and needs to
be deemphasized before encoding.
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LFE Channel Low-Pass Filter: Select this checkbox to apply a 120 Hz low-pass filter to the low-
frequency effects (LFE) channel. Turn off this filter if the digital signal fed to the LFE’s input
doesn’t contain information above 120 Hz.
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Full Bandwidth Chan. Low-Pass Filter: Select this checkbox to turn on a low-pass filter with a
cutoff near the available audio bandwidth that is applied to the main input channels. If the
digital signal fed to the main input channels doesn’t contain information above the available
audio bandwidth, you can turn off this filter, and Compressor automatically determines the
available bandwidth.
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Full Bandwidth Chan. DC Filter: Select this checkbox to turn on a DC high-pass filter for all input
channels as a simple way to remove DC offsets. Most mixed audio material is already free of
DC offsets.
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Surround Channels 90º Phase Shift: Select this checkbox to generate multichannel AC-3 streams
that can be downmixed in an external two-channel decoder to create true Dolby Surround–
compatible output.
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Surround Channels 3 dB Attenuation: Select this checkbox to apply a 3 dB cut to the surround
channels of a multichannel film soundtrack being transferred to a consumer home theater
format. Cinema surround channels are mixed 3 dB “hot” (higher) relative to the front channels
to account for cinema amplifier gains.