Apple Compressor 3 - Manual (Page 144)

LFE Channel
• Apply 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 does not contain information above 120 Hz.
Full Bandwidth Channels
• Apply 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 does not contain information above the available
audio bandwidth, you can turn off this filter. Compressor will automatically determine
the available bandwidth.
• Apply 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.
Surround Channels
• Apply 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.
• Apply 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.
General Information About Creating Dolby Digital Professional
Files
Following are some things to keep in mind as you configure and encode Dolby Digital
Professional AC-3 files.
About the Source Media Files
There are a few guidelines to be aware of when encoding Dolby Digital Professional
output files from your source media files.
Depending on the format, a file can contain a single channel (mono), dual channels
(stereo), or multiple channels. Compressor supports Dolby Digital Professional in all these
configurations.
Sound files intended for Dolby Digital Professional encoding must conform to the following
rules:
• All source files should be the same length. (If they are not, Compressor sets the length
of the AC-3 stream to match the length of the longest file.)
• All files must have a 48 kHz sample rate (as required for DVD).
144 Chapter 10 Creating Dolby Digital Professional Output Files