Highly acclaimed by a large majority of professionals, MP3 now appears on the computers of the astute Internet users. Have you never dreamed of compiling more than 150 tracks on a sole CD or to store the equivalent of 12 albums on that same CD? Well, it is now possible, thanks to MP3 format.

MP3 (Mpeg Audio Layer 3) is a compressed sound file obtained by deletion of data. MP3 is recommended by Moving Pictures Expert Groups (MPEG).

This format is close to the one used by Sony with the MiniDisc reader/recorder. Contrary to the DAT, MP3 and the MiniDisc works by deletion of data. Did you know that your favourite radio stations use this format? All your songs are stored on a server. The programming of the song to be heard on the air is done by computer. The computer then reaches for the MP3 files on the server after which a decompression board (speed gain) transforms them in typical sound files of CD quality to be transmitted on the air. Gone is the time when one had to get his vinyls in the basement.

Mpeg Layer-3 encoding allows to reduce by 12 times the size of an ordinary audio file. The main interest of this format is that it allows to reach a very important ratio of compression without loosing sound quality. This process is obtained by deletion of areas in the passing strip (or band) where the frequencies are inaudible by the human ear. The ear can not make the difference between the original sound from a CD and the same CD encoded in MP3.

Ergo, the advantage is the gain of vital space. With a 1:12 compression ratio, the files become more manageable in size (4Mo for 3 minutes of sound) and more adapted for transfer on the Net. Let's have an example: With a 4 minutes audio recording in CD quality (Stereo, 44.1 Khz, 16 bits), we can easily reach 50 Mo for a WAV file. After encoding in MP3, the file will not exceed 4 Mo without lost in sound.

The reading of such files is done via dedicated software that allow the decoding (decompression) of these files. However, to benefit from this, one must have a configuration powerful enough (Pentium) to perform the decoding of this type of files in real time.

What does MPEG Audio Layer 3 means? MPEG is a working group within a sub committee of International Standards Organisation (ISO) and International Electro technical Commission (IEC) who establish standards for audio and video compressions.

The algorithm are not defined by MPEG. MPEG describes methods to test the compressed data and test the decoders associated to the standard. MPEG also publish all technical reports.

MP3 format is an integral part of MPEG-1 video format (MPEG-1 format was used by the CDI from Phillips).

MPEG-1 has almost disappeared today and is being replaced by MPEG-2 (DVD). The audio MP3 format is always in use but under an improved form. MPEG-3 and MPEG-4 will be the new standards for high definition TVs.

MP3 format has been developed by the Fraunhofer institute in Germany. The first developments took place in 1987 and the first software exploiting this format appeared 3 years ago.

There are 3 under layers of audio encoding in MPEG-1 format and MPEG-2, Layer-1, Layer-2 and Layer-3.

Is MPEG-3 the same as Layer-3? NO, Layer-3 is uniquely the audio encoding part of MPEG standards.

From Layer-1 to Layer-3, the encoding methods and performances (Quality/Size) increase. Layer-3 is the latest evolution of audio encoding. The 3 layers, Layer-1,2,3 keep an ascending compatibility.