Image Processing Reference
In-Depth Information
K-1 A Variety of Audio Formats (Continued)
Format
Description
AC-3
A surround-sound format developed by Dolby Laboratories.
AIFF
CD audio ingested into a Mac OS system is stored in AIFF
files. The data rate is around 172 Kbps.
ALS
A lossless audio codec being developed as part of the
MPEG-4 standard.
Apple Lossless
This is a codec that is only available in iTunes and QuickTime
on version 6.5.1 and above. This codec is very good at
compressing audio for archival purposes or when you want
guaranteed lossless encoding. It will reduce an audio file to
about 50% of the original size, but it is not designed as a
deployment codec. The Apple Lossless codec could be useful
for embedding audio into applications or games.
ASPEC
A DCT-based audio-encoding standard.
ATRAC
The audio codec used for MiniDisc players.
ATRAC3 plus
A more advanced version of the proprietary Sony
ATRACS format. Used in MiniDisc players. Reputed by some
experts to be superior to MP3.
HE-AAC
High-Efficiency AAC. Another name for AAC plus.
IMA 4:1
This codec is good enough quality to retain 5.1
surround-sound encoding and output it intact. IMA
compresses to about 25% of the original size and it is not
variable. It is supported in QuickTime and Microsoft video
for Windows. This could be good for storing content on a
home media server where you very definitely want the
surround sound to come back out properly.
MACE
Macintosh Audio Compression and Expansion is a very old
codec from when 8-bit computers were used. It is useful to
have a MACE playback mechanism for it but no new content
should be converted to MACE.
MP3 format
MPEG-1 layer 3 audio files have been used to exchange
audio for some time. They are somewhat lossy, but having
tools to extract raw audio from them may get you out of
trouble occasionally. The quality of MP3 content is generally
considered good enough for consumption. Bit rates lower
than 128 Kbps may not deliver sufficient quality. There are a
lot of tools for creating MP3 files and many playback
applications and portable products. MP3 is likely to be
superseded by AAC in the future. The main attribute is total
ubiquity—MP3 audio is available virtually everywhere.
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