Apple Compressor 3 User Manual download pdf (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

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Apple Compressor 3 User Manual Page 144