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The MP3 is a fresh discovery in digital music and sound. Before MP3, there was the compact disc (CD). The audio on a CD is translated from an analog source like a master tape, but now most audio is saved directly as digital.
The MP3 process removes those sounds we can’t hear to simplify the data stream to make it more compressible. The idea is to alter things so that the removed data does not affect the quality of the audio.
MP3 cannot create CD-quality audio since it removes data from the data stream. Instead, it is called near-CD quality or FM quality, but the compression ratio attained is truly notable.
The MP3 process allows us to identify how much data is removed. For some, it’s fine expanding the lossy part of compression since they listen to MP3s in a noisy environment like in a car or in the office. In a noisy environment, you won’t hear the most delicate sounds, so it makes sense to optimise for file size rather than audio quality.
If you’re listening to music in a quiet environment, like your living room, you may be more conscious of the loss of quality and not so bothered by file size.
The lossy process tuning knob is known as the bit rate. Bit rates are quantified in bits per second. MP3 ranges from 96kbps to 320kbps. At the low end of the scale, 96kbps or 128kbps is comparable to FM radio. At the high end of the scale, 256kbps to 320kbps is comparable to a CD.
A CD transmits data at a rate of 176KB/s, or 1,400kbps. This means that a song recorded at the 96kbps bit rate is about 1/14 of the size of a CD track. At the 256kbps bit rate, files are roughly 1/5 of the size.
For example, if a car’s CD player can play MP3 CDs or data CDs with MP3s, you can put five times as many 256kbps bit rate MP3 tracks on the CD as you could on a standard audio CD.
Several experiments have been carried out and it revealed that, in general, people can’t tell the difference between an audio track encoded as a 256kbps MP3 and one from a CD. The only substantial statistic is that if you know a particular track very well from CD, you’re more likely to spot an MP3-encoded version of it than if you’re listening to a track you’ve never heard before.
The MP3 file format was intended to hold more than just the lossy-compressed audio data. The file contains a set of MP3 frames, each containing a header and corresponding data.
A set of frames may be inserted in a tag to specify that the frames are describing something special, like metadata about the MP3 track such as the artist’s name, title, album, track number, musical genre, album art, etc.
On playback, the metadata tags are read by the audio player and relevant information are displayed to the user. Although many CD rippers create metadata for your tracks and set them in the MP3 files, there are MP3 tag editors that let you alter the metadata at a finer level, or in block mode.
MP3s have changed the music environment for good. Although you can still buy CDs and even vinyl, most people consume their music through MP3.
Online sellers like Amazon and iTunes allow you to buy MP3s for immediate download and enjoyment. Online radio stations allow you to listen to lossy-compressed streamed tracks without the need for purchase.
Applications like iTunes and Windows Media Player allow you to rip your CDs as MP3s onto your hard disk for later listening. Audio players such as the iPod allow you to listen to your MP3-encoded music wherever and whenever you want to. MP3s are here to stay.