Digital Sound & Music: Concepts, Applications, & Science, Chapter 5, last updated 6/25/2013
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File Type Platform File Extensions Compression Container Proprietary DRM
PCM cross .pcm no no no no
RAW cross .raw no no no no
WAV cross .wav Optional (lossy) yes, RIFF
format
no no
AIFF Mac .aif, .aiff, no yes, IFF
format
no no
AIFF-C Mac .aifc yes, with various
codecs (lossy)
yes, IFF
format
no
CAF Mac .caf yes yes no no
AU Unix/Lin
ux
.au, .snd optional -law
(lossy)
yes no no
MP3 cross .mp3 MPEG (lossy) yes license required
for distribution or
sale of codec but
not for use
optional
AAC cross .m4a, .m4b,
.m4p, .m4v,
.m4r, .3gp, .mp4,
.aac
AAC (lossy) more of a
compression
standard than
a container;
ADIF is
container
license required
for distribution or
sale of codec but
not for use
WMA Windows .wma WMA (lossy) yes yes optional
OGG Vorbis cross .ogg, .oga Vorbis (lossy) yes no, open source optional
FLAC cross .flac FLAC (lossless) yes no, open source optional
Table 5.1 Common audio file types
AIFF and WAV have been the most commonly used file types in recent years. CAF files
are an extension of AIFF files without AIFF's 4 GB size limit. This additional file size was
needed for all the looping and other metadata used in GarageBand and Logic.
All along the way as you work with digital audio, you’ll have to make
choices about the format in which you save your files. A general strategy is
this:
When you’re processing the audio in a software environment such as
Audition, Logic, or Pro Tools, save your work in the software’s
proprietary format until you’re finished working on it. These formats
retain meta-information about non-destructive processes filters, EQ,
etc. applied to the audio as it plays. Non-destructive processes do not
change the original audio samples. Thus, they are easily undone, and
you can always go back and edit the audio data in other ways for other
purposes if needed.
The originally recorded audio is the best information you have, so it’s always good to
keep an uncompressed copy of this. Generally, you should keep as much data as possible
as you edit an audio file, retaining the highest bit depth and sampling rate appropriate for
the work.
At the end of processing, save the file in the format suitable for your platform of
distribution (e.g., CD, DVD, web, or live performance). This may be compressed or
uncompressed, depending on your purposes.
Practical
Exercise:
Audio File
Compression
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