Apple Compressor (4.0) - Manual (Page 72)

Chapter 5 Custom settings and output formats 72
Use the Frame Rate pop-up menu to choose from the following options:
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23.98: Used for NTSC-based video
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25: Used for PAL-based video
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29.97: Used for NTSC-based video
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50: Used for PAL-based video
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59.94: Used for NTSC-based video
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Average Bit Rate: Use the slider to choose an average bit rate to use for the output video,
or enter a value in the field. Although the available range for a Blu-ray disc is between 5
Mbps and 30 Mbps, typical video bit rates with H.264 might range from 7 Mbps to 15 Mbps,
depending on your DVD bit budget and the nature of your source media files. The available
range for AVCHD discs is 5 Mbps to 15 Mbps.
•
Maximum Bit Rate: Choose a maximum bit rate between 6 Mbps and 35 Mbps for a Blu-ray
disc, or between 6 Mbps and 17 Mbps for an AVCHD disc. You can also enter any number
within these ranges in the accompanying field. The Maximum Bit Rate setting cannot be
lower than the Average Bit Rate setting. As a general rule, set your maximum bit rate at least 1
Mbps higher than your average bit rate, to allow for bit rate variability in achieving the goal of
constant quality.
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Multi-pass: Select this checkbox to turn on multi-pass encoding. Similar to two-pass MPEG-2
encoding, multi-pass offers the best possible quality. For faster (single-pass) encodes, turn this
feature off by deselecting the checkbox. For more information, see
Job segmenting and two-
pass or multi-pass encoding on page 249.
4 Click Save As.
Dolby Digital Professional files
Dolby Digital overview
Compressor provides the tools you need to encode and batch-encode Dolby Digital Professional
(AC-3) audio files.
Dolby Digital Professional format (also known as AC-3) is a very common compressed audio
format for DVD-Video discs. Compressor accepts multichannel sound files in a variety of formats
and gives you complete control over the AC-3 encoding process. Dolby Digital programs can
deliver 5.1-channel surround sound with five discrete full-range channels (left, center, right, left
surround, and right surround) plus a sixth channel for low-frequency effects (LFE), sometimes
known as “the subwoofer.” Another surround option is Dolby Surround, with four channels
(left, center, right, and surround). But not all AC-3 audio is 5.1 surround sound. Dolby Digital
Professional is commonly used to encode stereo files to greatly reduce their file size.