An MP3 Primer A-1
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An MP3 Primer
What is MP3?
MP3 is an acronym for Moving Picture
Experts Group (MPEG) Layer 3, a type of
audio data compression that can reduce digital
sound files by a 12:1 ratio with virtually no
loss in quality. It is an efficient way to store
high-quality music or other audio content on
your computer.
MP3 files can be very small and yet retain a
high sound quality. MP3 files usually have the
extension .mp3, and can be downloaded from
the Internet, or can be legally made for
personal use from the audio CDs that you
purchased.
It is illegal to encode MP3 files for
trade or sale unless you have the
expressed and explicit permission of
the copyright holder(s).
MP3 Conversion Process
Extracting from Audio CD
You must have a CD-ROM drive that
can extract the audio data from an
audio CD.
Audio CD extraction is the first phase in the
MP3 conversion process. It is the reading of
data off an audio CD and storing it temporarily
on your hard drive.
You need an application that can direct the
CD-ROM drive to extract this audio data. This
program is known as a “ripper”. It reads the
data off the audio CD and in some cases stores
it in a file.
The duration of the audio CD extraction phase
depends on many factors. The speed of a
CD-ROM drive is one of the most important
elements in overall extraction speed. The
speed ratings commonly seen on CD-ROM
drives—like 8X, 24X, and so on—refers to the
speed in reading data CDs or CD-ROMs. Your
particular drive may be fast for non-audio data,
but slow at reading audio CD data.
Other factors are defects or scratches on an
audio CD. When playing the audio CD in a
CD-ROM drive, the data lost due to error is
negligible. But when data is read incorrectly
and put through the MP3 encoding phase, the
distortion is highly noticeable. To avoid this
distortion, the audio CD extraction software
may read the data two or three times to make
sure it was read correctly. This error-checking
feature is an option in most audio CD data
extraction software. Be sure error-checking is
enabled in your audio CD extraction software.
Encoding to MP3
The data extracted from an audio CD is one of
the many types of data an MP3 encoder may
process. Encoders typically expect data to be
in .wav format. They read .wav data and output
MP3 data. These data are put into an MP3 file.
MP3 encoding is the compressing of data by
transforming it into the frequency domain.
MP3 encoding/compression is quality lossy
compression and the amount of loss (of
quality) is dependent upon the sampling rate
of the output and the bitrate of the output. The
