What Is MP3
- What is MP3?
MP3 is a compression form (like .zip). The name MP3 stands for Mpeg 1 Audio Layer 3 and its compression algorithm is based
on a complicated psycho-acoustic model. This model is based on the fact that the human ear cannot hear all the audio
frequencies. The human hearing range is between 20Hz to 20Khz and it is most sensitive between 2 to 4 KHz. This MP3 model
among other techniques tries to eliminate the frequencies which the human ear is unable to hear keeping all the hearing
frequencies, therefore leaving intact the hearing experience. As a result the MP3 compression form is destructive. That
means that the compression algorithm causes the file to lose some information so that it cannot be restored to its
original content.
When compressing an audio file (encoding) using the MP3 algorithm you can set the desired encoding level and have any
compression level you want. The larger the compressed file the better the audio quality of the result. The majority of the
files available on the internet are encoded in 128 kbits stereo 44khz which results to a high quality file that is 12
times smaller than the original!! This of course has many interesting consequences:
1. It is possible to create CDs that contain over 160 songs and can play for over 14 hours on a PC.
2. We can efficiently store songs on a hard disk and play them directly form there.
3. We can easily transmit a song over the internet (a compressed 4 minute song is smaller than 4MB,
while uncompressed would be over 40MB). That's why MP3 has become the hottest keyword in the Internet.
The main disadvantage of the MP3 format is that it needs to be decompressed when played. That means that we need a computer
to play them or that we need a device specifically designed to support the mp3 format.
- How do I play an MP3 file?
You just need an MP3 player. There are innumerous free players for download in the internet, such as
Winamp, Windows Media Player and
Real Player.
- Why Compress Audio?
There is a simple reason to compress digital audio. High quality uncompressed digital audio takes a lot of space. Just 1
minute of CD quality uncompressed audio takes around 10Mb and needs around 50 min to be transmitted over a 28.8 modem.
Digital audio coding tries to compress digital audio so as to take less space. Modern perceptual audio coding techniques
like MP3 (MPEG Layer 3) use the human ear perception of sound to achieve compression factors of 12 with no perceptible
loss of quality.
- The Two Parts of Audio Compression
Audio compression consists of two parts:
1. The Encoding which transforms digital audio data into a highly compressed form called bitstream (or coded audio data).
2. The Decoding which reconstructs digital audio data from the bitstream. This is absolutely necessary if you want to play
the bitstream on your soundcard.
- Audio Quality
Please note that what you end up with after encoding and decoding is not the same sound file anymore. Redundant and irrelevant (for the human auditory system)
parts of the sound signal are changed. The reconstructed audio file differs from the original, but
it will sound the same - more or less, depending on how much compression had been performed on it.
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