What is an MP3?
Limited network bandwidth and hard disk capacity have been major driving
factors behind the development of compressed audio formats. Until
recently, only a small number of people used their computers to store
CD-quality music. A few people would copy their favorite songs from
a music CD and use a CD-Recordable drive to create a compilation CD,
similar to the way many people make cassette tapes from prerecorded
music.
Audio and electronics engineers have been working to solve the bandwidth
bottleneck ever since networks were invented. They work on both sides
of the problems by increasing bandwidth (larger pipe) and compressing
data (higher pressure). High-speed Internet connections such as cable
modems and ASDL have been developed to increase the size of the pipe,
and compression schemes such as JPEG and MPEG have been developed
to squeeze more data through it.
MP3 provides relief by compressing files up to approximately 10:1
without significant loss of quality. Four minutes of CD audio (44.1,
kHz 16-bit stereo) requires about 40MB of disk space and would take
more than 3-½ hours to download with a 28.8 kbps modem. At this rate,
a 2GB hard disk would hold about 50 four-minute songs.
With MP3 encoded at 128 kbps, each four-minute song would take up
less than 4MB of space and could be downloaded in less than 20 minutes
with a 28.8 kbps modem. A 2GB hard disk could now hold more than 500
songs. This much compression, coupled with the larger and cheaper
hard disks that are now available, makes it possible to use a PC as
a high-capacity, CD-quality jukebox in place of tape decks, turntables
and CD players.
Newer generations of MPEG Audio, such as AAC (Advanced Audio Coding),
offer even higher levels of compression and better sound quality but
have not yet reached the consumer market because of high licensing
costs.
Relatively low file size and high quality makes MP3 files an excellent
medium for artists to distribute complete songs on the Internet, as
most are near CD-quality. Special but easily obtainable software is
necessary to playback and make MP3s.
The factor that greatly influences MP3 quality is the bit rate. Measured
in kilobits/second (kbps), the bit rate determines the maximum compression
used to encode the file. Generally, the higher the bit rate, the better
the sound quality. Most MP3s are encoded at a bit rate of 128 kbps,
which produces excellent CD-quality audio with a reasonable compression
rate of about 1/10 of the original file size. It is not uncommon to
find MP3s encoded at such bit rates as 256 kbps or 160 kbps, and
these will have even better sound quality, but file size will be somewhat
larger.
Also contributing to the sound quality is the sample rate. Basically
the sample rate (measured in Kilohertz) determines the spectral range
of sound that is available in the digital recording. Sample rates
generally range from 8 Khz to 48 Khz, with 44.1 being the standard
for music recordings, and 8 Khz is basically telephone-quality (perfect
for voice recordings). As with the bit rate, the higher the sample
rate, the better the quality of the MP3.
The majority of the preceding section (II.A.1) was taken with permission
from The MP3 and Internet Audio Handbook by Bruce and Marty Fries.
You can read this book or order it online at www.mp3handbook.com.
Can I convert my MP3 files back to Audio CD format? (WINDOWS)
Yes you can, and in fact one of the best features of MP3s is you
can produce your own mix CD's to listen to in your car or home stereo.
All you will need is Winamp or CDEX 1.20, a CD
Recorder, and CD Recorder software. First you must stream the audio into WAV format as most CD Recorders
are configured to recognize WAV files, not MP3s.
For Winamp, just click on the icon in the upper left
corner and then click Options -> Preferences (or hit Ctrl+P from WinAmp). Then under plug-ins click Output
and select the Nullsoft Disk Writer plug-in. Next select the directory where you want the wave files to be
stored. Now, whenever you play an MP3 it will streamed into a WAV file (you will not hear anything, so
don't worry if there is no sound). Make sure you do not have "Repeat" selected as WinAmp will continue to
decode these over and over if you do. Set WinAmp back to play mode
by going to Options -> Preferences -> Output Plugins and selecting
the wave-out plugin.
Using CDEX, all you have to do is click on the button that says MPEG
-> WAV. It is located on the right side of the window. Then just select
the MP3 file you wish to convert to a WAV file. If you need to change
the location where CDEX stored the new WAV file, just press F4, and
change the WAV -> MP3 directory to the one you desire.
The resulting WAV files will not sound any better than the MP3 files,
as anything lost in compression will not be regained. You can now
use these WAV files to be copied as audio tracks on a CD-R. Operation
of your CD-R is beyond the scope of this FAQ, so be sure to consult
the CD-R software documentation if you have any problems or questions.
.