How it began
In the early 1970s, Prof. Dieter Seitzer of Erlangen-Nuremberg University began working on transmitting speech in high quality over phone lines, and in the late 1970s his team turned to coding music signals. His student Karlheinz Brandenburg began applying psychoacoustic principles to audio coding. In 1987 the university and the Fraunhofer Institute for Integrated Circuits in Erlangen formed a research alliance within the European Union funded EUREKA project EU147 for digital audio broadcasting, led by Prof. Heinz Gerhäuser.
Before it existed
When the Compact Disc was presented in 1981, it stored audio as uncompressed linear PCM at 16 bits per sample. Earlier coding algorithms existed only as computer simulations, and because of the computing time required they could be tested with only a very limited amount of audio material.
How it works
The method builds on psychoacoustics, the properties of human hearing. Brandenburg's OCF algorithm, the subject of his doctoral thesis, already had features of the eventual format, including a high frequency resolution filter bank, non-uniform quantization, and Huffman coding. A joint stereo coding mode, developed by Jürgen Herre, was added later. Layer 3 offers near CD quality at less than 2 bits per sample.
How it spread
OCF was improved into a codec called ASPEC with contributions from Hannover University, AT&T, and Thomson, and it was proposed for the MPEG audio standard. MPEG combined proposals into three layers, with Layer 3 based on ASPEC. The first edition of MPEG-1 was released as ISO/IEC 11172 in August 1993. The Fraunhofer-Gesellschaft and Thomson set up a joint license program.
What changed first
The first real application was sending speech and music between broadcasting studios over ISDN lines, using studio racks that Fraunhofer IIS made and sold to radio stations. Layer 3 then became a popular way to store music on the small hard disks of PCs and to transfer music files over the internet through modems. Fraunhofer IIS also built a prototype portable player without moving parts. According to the Fraunhofer-Gesellschaft, around 10 billion devices have been licensed. Fraunhofer IIS went on to co-develop AAC and later audio codecs.
