On this page ...
So what is MP3 and why should I use it ?
On this page I briefly explain why you should
use MP3, what is in it for you? Do you need it? I also explain a
little about the available compression techniques, how to create
MP3's and how to playback MP3's.
MP3 has become more and
more popular - mostly due to the Internet - the last few years as
THE format to exchange music.
First of all: More music fits on one CD.
A song in MP3 format can be up to app. 10 times smaller
(!!!) than the same song on a regular audio CD. MP3 is still very close
to CD quality. Smaller does not mean smaller in playback time, but smaller
in needed storage space.
To give you an impression: A regular audio CD holds
between 10 and 15 songs.
A CDRom filled with MP3 songs, holds between 100 and 180 songs (average).
As you can see: a very big advantage.
Imagine you throw a party. Before MP3 you had to swap CD's every now and
then. Now, using MP3, you can put one single CD in your playback equipment
and have music all night long (app. 10 hours) without having to change
Second: Sending/Receiving over te Internet is faster.
Since an MP3 is a lot smaller, you can imagine that
sending it or receiving it will take less time too. As an example; a regular
song on an audio CD takes about 34 Megabyte of space. The same song, in
MP3 format, will take just 3 Megabytes. Besides the fact that most e-mail
providers do not allow you to send attachements of over 4 Megabyte, you
can image that 3 Mb takes less time than 34 Mb.
Third: Free downloadable music on the Internet.
Upcoming "sharing" tools like WinMX, KaZaa
and eDonkey allow you to download entire CD's in MP3 format. MP3 has become
the standard for exchanging music on the Internet.
Would be nice to be able to use this too, wouldn't it?
Forth: More and more portable playback equipment.
Small files offers the capability to create miniature
playback equipment for MP3. Now-a-days the playback equipment can be found
in little gadgets the size of a pack of Marlboro's. Not only that, more
and more equipment is capable of handling MP3. Some examples: MP3-CD-Walkmans,
Car-radio's, DVD players, etc.
In general, compression is used to reduce the
storage size of data for purposes like transportation, storage, backups,
etc. With current computer power it is not only a matter of space, but
of speed as well. Compression can be either lossless or not-lossless.
An example of lossless compression would be computer
software. If parts of the original software got lost, the program would
not work anymore. A well known example of such compression is to be seen
in programs like WinZip.
For Audio and Video, it often doesn't matter to loose
a little bit of information. Some examples are MPEG-1, MPEG-2, MP3 and
MPEG-4 (DivX). All of
these are suitable for both Audio and Video, with the exception of MP3
which can only be used for Audio.
The amount of data needed for a not compressed audio
file can become huge. A 3 minute song can exceed 34 Mbytes ... Lets' take
a look at a small calculation to give you an idea why this is.
Suppose we want to record a 1 minute song to our computer
harddisk. Naturally, you would like to have it in CD quality, so a minimum
sample rate of 44.1kHz (=44100Hz) is needed using a 16 bit (2 bytes) format.
44100 Hz means that we sample 44100 values per second
form the anaolog digital converter of your soundcard. We need to multiply
this by 2, since we want stereo audio (left and right channel). Since
we use 2 bytes (16 bit resolution), we need to multply this by 2 once
|So the size of 1 minute of music
becomes a file of:
||samples per seconde
||stereo: left and right
||bytes per sample
||seconds in 1 minute
||App. 10 MBytes
Suppose you would like to download this from the Internet,
using a 28k8 modem. It would take you 45 minutes download time
- for JUST 1 MINUTE! To save this, you would need also 8 disks (1.44 Mb
3.5" diskettes) to store it.
So compression can be pretty usefull. Our 1 minute music
could become a 1 Mbyte file using MP3 compression.
There are different (combinable) forms of compression.
Let me explain this very simple (take it from me: in practice, this is
much more complicated).
For example, if data contains repeating patterns, we
should be able to say "repeat pattern". So, say we have this
we could also write it down as:
10 x ABCCDD
The result is obvious: this is shorter, but still holding
the same information. This is compression!
A different technique is converting a pattern to a mathematical
Suppose we have this pattern of values:
0, 1, 4, 9, 16, 25, 36, 49, 64,
81, 100, 121, 144, 169, 196, 225, 256, 289, 324, 361, 400, 441, 484, 529,
576, 625, 676
This matches the values 1 t/m 27 for X in the formula:
Y = X^2 (so X to the power 2).
So we write down:
X=1...27, using Y=X^2
Once more: this is shorter too.
I have to admit that this is a very very simple example, but it's the
principle that matters.
What we can't hear, what we can't see.
Here we use the boundaries of the human senses. We -
humans - can only hear sound in the range of 20 to 20.000 Hertz. CD recordings
often hold an even wider range. By removing that extra part, we gain once
more. The files becomes smaller,
That's not all. Some very short transitions (and I mean
REALLY short onces) can not be detected by the human ear. So we skip those
as well, once more the file becomes smaller.
We can do something similar with video: Can you come
up with 5 colors? Now tyr 16 colors. Getting hard? Well try 16 Million
colors - pretty impossible isn't it? Our vision can be tricked too and
does not distinct 16 million colors. So we leave out what can't be seen
There is yet another compression technique used mainly
Video is basically a large collection of seperate images,
displayed sequentially at app 25 to 30 pictures per second. Instead of
storing and drawing each and every picture, we could also limit drawing
and storing to the difference between this picture and the previous picture.
So we store the first complete picture. Next we store the difference between
picture1 and picture2 and so on. MPEG is using just that type of compression.
Audio compression use has two sides.
First of all, in order to get a compressed song, we
need to encode the normal song. Encoding is the activity of transforming
digital data into a different (highly compresses) format, called a bitstream.
To be able to hear this song, we need to decode it again. The bitstream
to needs to be decoded before we can send it to our soundcard. Decoding
is the process where a compress bitstream is being tranformed into it's
De software needed for encoding, is called an audio
encoder. Frauenhof is one of the first onces to create such an encoders.
Decocing software, is called a decoder like for example WinAmp.
Sometimes both encoder and decoder are combined in a so called CODEC.
Ratios, Bitrates and Quality
Note: Since MP3 is a compression technique
with loss of information. This means that the decoded file will not be
100% identical to the original!
In general, the lower the compression ratio, the better
the quality and vice versa. However, the lower the compression ratio,
the larger the resulting file.
A compression-ratio is a somewhat vague, experts use
therefor the so called bitrate to express the quality. Bitrate indicates
the average amount of bits per second used for audio in the compressed
bitstream. Usually expressed kbps, which stands for kBits/s,
or 1000 bits/s. The number of bytes is found
by dividing bits/sec. by 8. There are two types of bitstreams a Constant
Bitrate, where the bitrate remains constant. The other is called Variabele-bitrate.
The trick here is to lower the bitrate (which improves compression-ratio)
when there is no need for such a large bitstream. Using this technique
makes it rather hard to predict the size of the file after compression.
The resulting size of the compressed file using MP3
compression can be up to 12 times smaller than the original. In our example
the 10 Mb data (our piece of 1 minute music) can be reduced to say 800
Kbyte, which takes about 3 minutes using your 28k8 modem to downloaden!
Compressing songs to MP3 can be done using several tools.
One of the more advaced tools, Nero,
has en encoder buildin making it easy to use. See How
to create MP3's page for more details.
Other software will offer similar features, but I prefer
Nero. You'll have to find details on those programs elsewhere.
Cosmo's MPEG Suite is a pretty easy to use tool.
Radium has adapted the original Frauenhof codec, which
can be download here.
AudioGrabber is also a cool piece of software for ripping
(the process of copying a song on a CD to your PC) and it also supports
MP3 codecs, for details see their official
Another freeware MP3 codec is Plugger, which you can
download from the Plugger
Both Xing (Xing
MP3 encoder) and Frauenhof (Frauenhof
institute) offer commercial MP3 tools. They are pretty good, don't
forget however that Xing is know to create some ompatibility issues.
How to playback
You cannot just playback an MP3 on any CD-player or
1. Using your PC.
If your PC has a minimum of a Pentium 166 Mhz (Yeah,
yeah,... I know: that's a really old PC!), then this PC will be suitable
for MP3 playback. For Windows,
Linux as well as Macintosh
operating systems, playback software is available.
Recent Windows versions come with the Windows Media
Player, which is capable of MP3's playback.
One of the widely spread applications, and in my opinion
easy in use, is WinAmp.
WinAmp is free and
can be downloaded at their website.
After installation of WinAmp, you can either double
click MP3 files, or drag-and-drop files onto WinAmp.
2. Using a suitable DVD.
More and more DVD players out there are capable
of MP3 playback. Brands like Yamakawa,
are known for their MP3 capabilities. Take a look at the Conrad
website they sell these players too.
3. Portable MP3 players.
They come in several flavours:
- Memory based (some have removable memory, some don't)
- CD based (looks like a CD Walkman)
- Harddisk based (often refered to as a "jukebox")
4. MP3 compatible car-radio.
Several brands, including Kenwood,
Aiwa and Kingstech,
sell MP3 capable car-stereo ...