Apple Compressor (4.0) - Manual (Page 106)

Chapter 5 Custom settings and output formats 106
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Use Variable Bit Rate Encoding (VBR): Select this checkbox to have Compressor vary the number
of bits used to store the music depending on the complexity of the music. This can help keep
file size to a minimum.
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Sample Rate: Choose the number of times per second that the music waveforms are captured
digitally. The higher the sample rate, the higher the quality and the larger the file size. Don’t
choose a sample rate higher than the rate used originally to store the music or you’ll waste
space. CD quality, for example, is 44.100 kHz, so choosing a higher rate when you’re encoding
from a CD is unnecessary.
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Channels: If you don’t have stereo speakers or if your audio files are monaural, choose Mono
(mono files are about half the size of stereo files). If you’ll be listening to your MP3 files using
your stereo system, choose Stereo.
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Joint Stereo: When this checkbox is not selected, your MP3 files contain one track for the right
stereo channel and one track for the left. In many cases, the two channels contain related
information. When the Joint Stereo checkbox is selected, one channel carries the information
that’s identical on both channels, and the other channel carries the unique information. At bit
rates of 160 kbps and below, this can improve the sound quality of your converted audio.
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Smart Encoding Adjustments: Select this checkbox to have Compressor analyze your encoding
settings and music source, and then adjust settings to maximize quality.
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Filter Frequencies Below 10 Hz: Select this checkbox to have Compressor filter inaudible
frequencies, resulting in smaller, more efficient files without perceptible loss of quality.
4 Click Save.
MPEG-1 files
MPEG-1 overview
MPEG-1 is an internationally accepted compression standard developed by the Motion Picture
Experts Group (MPEG). MPEG-1 allows you to create VHS-quality video files and was designed to
support SIF (Standard Interface Format) non-interlaced (progressive) video using relatively low
bit rates. (Compressor supports 0.5 Mbps to 2 Mbps.) It also allows you to create compressed
one-channel and two-channel audio.
MPEG-1 is a widely adopted standard, so it can be used in many distribution methods, including
optical discs, the web, and audio-only files.
DVD, VCD, and CD-ROM
MPEG-1 is the video compression format used for video CD (VCD) titles and is compatible for use
on DVD titles since all DVD players contain the hardware required for MPEG-1 playback. MPEG-1
is commonly used in videos distributed on CD-ROM. Its low bit rate and small file sizes are useful
when you must fit multiple hours of video onto a DVD and do not require the broadcast quality
of MPEG-2 encoding. A DVD can contain a mix of MPEG-2 and MPEG-1 video.
On the web
Because MPEG-1 was one of the first widely adopted compression standards, it has the
advantage of being compatible with most media players. This makes MPEG-1 attractive for use
on the web when you need maximum compatibility with relatively high quality.
Audio-only files
You can use MPEG-1 Layer 2 audio compression as an alternative to Dolby Digital Professional or
DTS compression for DVDs. For details, see
Create MPEG-1 audio for DVD on page 110.