Background of MP3

MPEG 1 layer III standard commonly known as MP3 is a complex audio compression method.  The algorithms were approved in 1991 and were standardized as MPEG-1 by the Motion Pictures Expert Group (MPEG) in 1992.  It was formed by the ISO/IEC organizations coding standard as ISO/IEC 1172-3 in 1993 .

The standard defines layer I, II and III. The layers increase complexity in terms of less transmission bandwidth is required.  Layers III is the most efficient due to its high quality coding of near to CD audio at a ratio of 12:1. Table below shows the transmission rates and ratio required from each layers.

Coding method	Bit rate	Ratio
PCM CD audio	1.4 Mbps	1:1
Layer I	384 kbps	4:1
Layer II	192 kbps	8:1
Layer III	128 kbps	12:1

                                  

                                                 Table : Comparison of bitrate and Ratio