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cs276:nao.tutorial7

Tutorial 7

AIFF

AIFF, or audio interchange file format was born the same year as me, in 1988.
AIFF is generally a lossless raw audio format that stores audio samples as
pulse code modulated digital samples which translates to time-varying pressure data
(PCM).
The format does allow for compression, using the ULAW, ALAW, or G722 methods.
All of these compression methods are lossy, but it isn't really clear where
data is being lost or damaged in the compression process.
Oddly enough, AIFF is encoded in a Big-Endian number format that was derived from the
Motorola 68000 processor architecture.

AIFF on Wikipedia

WAVE

WAVE or waveform audio format, or even audio for Windows, is another raw
format for storing uncompressed audio sample as pcm data.
WAVE implements a lossy compression algorithm, though it is not commonly used.
When compressed the types of information lost may not be noticeable,
but depend on the target sample rate, bit depth, and on the amount of information
encoded in the file that is considered redundant or unnecessary.
For example, consider a track of uncompressed wave format audio encoded on a CD.
The audio would likely have a sample rate of 44.1khz, and a sample depth of 24 bits.
That would be a fairly high fidelity recording of some sound.
However, if that sound was then ripped to say a compressed wave file, on your
hardrive, and compressed to a 22khz sample rate, and a 16 bit sample depth,
then you would definitely hear the difference.
Both AIFF and WAVE support some forms of frequency specific compression
to encode for voice specific applications, though wave tends to be more
widely used outside of the Apple community. Particularly this is used for
voice over IP, or internet broadcast talk radio.

Wave on Wikipedia

AU

The AU file format was developed by Sun as a simple audio container.
The format can store data in a lossless uncompressed pcm format,
or store audio samples as compressed, and lossy, pcm.
The file header allows for the specification of 1-27 different ways
of storing the audio data, such that the bit depth, number of channels
and sample rate can be selected. The format was originally designed to
handle an 8 bit saple depth and to use a 64kbit/s bit rate, generated
from an analog signal at 8khz, but since the introduction of the
AU file header the versatility of the format has expanded.

AU on Wikipedia

cs276/nao.tutorial7.txt · Last modified: 2009/11/05 16:30 by nels_oscar