Adobe AUDITION 1.5 - Manual (Page 244)

CHAPTER 11 236
Saving, Exporting, and Closing Files
DVI/IMA ADPCM (.wav)
The International Multimedia Association (IMA) flavor of ADPCM compresses 16-bit
data to 4 bits/sample (4:1) by using a different (faster) method than Microsoft ADPCM. It
has different distortion characteristics, which can produce either better or worse results
depending on the sample being compressed. As with Microsoft ADPCM, use this format
with 16-bit rather than 8-bit files. This compression scheme can be a good alternative to
MPEG; it provides reasonably fast decoding of 4:1 compression, and it degrades sample
quality only slightly.
Options Choose from the following:
• 2 bits/sample, 8:1 produces files with the highest compression ratio (8:1) but with the
lowest number of bits. Select this option if smaller file size is more important than audio
quality. Keep in mind that this compression rate is less compatible than the standard 4-bit
and is supported on fewer systems.
• 3 bits/sample, 5.3:1 produces higher quality than the 2 bits option, but the quality isn’t
quite as good as with the 4 bits and 5 bits options. Some systems might have problems
playing back files with this compression rate, especially stereo files.
• 4 bits/sample, 4:1 produces 4-bit files at a compression ratio of 4:1. This option is the
default.
• 5 bits/sample, 3.2:1 produces files with the highest quality, since more bits and a lower
compression ratio are used. However, this compression rate is less compatible than the
standard 4-bit.
Microsoft ADPCM (.wav)
The Microsoft ADPCM format provides 4:1 compression. Files saved in this format
expand automatically to 16-bits when opened, regardless of their original resolution. For
this reason, use this format with 16-bit rather than 8-bit files.
Options Choose from the following:
• Single Pass (Lower Quality) compresses files in a single pass. Use this option if you’re in
a hurry. However, the quality is lower than if you use the Multiple Pass option. The time
taken to read an ADPCM-compressed file is the same no matter which option you use.
• Multiple Pass (Higher Quality) compresses files in multiple passes, providing better
quality. This setting is the default.
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