The magic of MP3

By Sagun Chalise,Sanjay Devkota, Sabina Bajimayo

MP3 stands for MPEG-1 layer 3 and is a standard technology and format for compressing a sound sequence into a very small file while preserving the original level of sound quality when it is played. MP3 files are identified by the file name extension "mp3". MP3 allows sound files to be compressed to such an extent that one minute of music takes approximately 1MB of disk space. 

We can now create CDs that contain over 150 songs and can play them for over 700 minutes on a PC. We can  now easily transmit a song over the Internet. That is why MP3 has become the hottest topic in the internet for few months ago. We cannot hear MP3 in our ordinary home stereo CD players.  Many MP3 players and songs are available for free download from a number of web sites. So anyone who has internet access can download those MP3 players and songs with just a few clicks of a  mouse.

The technology behind MP3

At the end of the eighties the Moving Pictures Expert Group(MPEG) was formed  to devise a suitable coding and compression scheme for trasnmitting moving pictures and recording in standard digital storage media such as CD-Rom,video CD etc.

For audio, MPEG-1 describes the compression of  audio signals using high performance perceptual coding schemes. It specifies a family of three audio coding schemes called Layer-1, Layer-2 and Layer-3. Each Layer not only offers increased compression but also increased encoding complexity. 

The purpose of Audio Compression

Before the advent of audio compression, high-quality digital audio track took a lot of harddisk space to store. Lets take an example of storing 1 minute of song in CD quality. CD quality digital audio consist of 16 bit samples recording at a sampling rate of 44.1 KHz.  44.1 KHz means that we have 44100 values per second per channel coming in from the source. The total disk space taken by this 1 minute two channel (stereo) song is given by 
44100 samples/sec X 2 channels X 16 bits/channel X 60 seconds=10 MB approx.

Playing MP3 songs

To play MP3 songs, we need a MP3 player, which we can download from a number of websites. Some of the popular players are Winamp (windows) , Macamp (Mac). However the minimum requirement for acceptable quality playing is a Pentium 75 MHz.

Making MP3

Making our own MP3 requires two processes- Ripping and Encoding. Ripping is the process of copying audio tracks from audio CD's to the harddisk in .wav file format and Encoding is the process of conversion of .wav files to the .MP3 files.

There are many rippers and encoders. It should be noted that not all the CDROM drivers can rip from the CD. We can also decode a MP3 file into a WAVE file using decoders. Some of the popular CD Rippers are WinDac32, CDDA-DAC, Audio Grabber. The all in one software is Music Match Jukebox, a shareware program and it allows us to copy audio tracks from the audio CD into Mp3 format in one step i.e.-it functions both as a ripper and an encoder. We can also play MP3 songs using this software.