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8.2. What is MP3?

The format known as MPEG-1, Layer III (or MP3 for short) was developed in the late 1980s and early 1990s and was finalized in November 1992 by the Motion Pictures Expert Group (MPEG) as part of the original MPEG-1 standard. The MPEG committee is a gathering of scientists and engineers who work under the auspices of the International Standards Organization (ISO) and the International Electro-Technical Commission (IEC). The members of the MPEG group are responsible for establishing standards for digital coding of moving pictures and audio. (See About the Motion Pictures Expert Group .)

MP3 is more than a simple compression scheme. Most people are familiar with file compressors such as zip. But if you've ever tried to zip up a WAV file, you've probably found that raw audio doesn't compress well at all. Compression shaves only a tiny percentage from the original file size. Instead, MP3 gets most of its compression from the science of psychoacoustics —the modeling of human auditory perception. The theory is that uncompressed audio streams carry a lot of data that isn't actually perceived by humans, for a variety of reasons. The logic follows: why store data that can't be perceived? MP3 encoders analyze audio streams and compare them to mathematical models of human psychoacoustics—a far more complex and mathematically intensive process than simple zip compression. The process is time- and processor-intensive (compared to zip, anyway), but it has the benefit of achieving more effective compression.


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