December 14, 2004 MP3, the world's most popular audio compression format is about to go multi-channel. Scientists and engineers from the Fraunhofer Institute for Integrated Circuits IIS, who developed MP3 together with colleagues from Thomson and Agere Systems, have joined to launch MP3 Surround into the consumer and commercial markets. This technology will enable 5.1 channel surround sound for a broad spectrum of applications including web-based music distribution, broadcasting systems, PC-related audiovisual or gaming applications, consumer electronics and automotive systems.
As previously reported in Gizmag, MP3 Surround supports high-quality multi-channel sound at bit rates comparable to those currently used to encode stereo MP3 material, resulting in files half the size of common compressed surround formats. At the same time, the new format offers complete backward compatibility to any existing MP3 software and hardware devices.
MP3 basics
MP3, short for MPEG-1/MPEG-2 Layer 3, is a format for storing digital audio. It uses an advanced type of audio compression, which reduces the file size with little reduction in audio quality. MP3 is used in software applications, digital audio players, home stereo devices and music distribution over the Internet, but is also used for other purposes such as real-time digital audio transmissions over ISDN. Over one billion music tracks are currently downloaded every month on the Internet using MP3 according to Thomson MP3 licensing.
The history of MP3
In the 1980s, the International Organization for Standardization (ISO) and the International Electrotechnical Commision (IEC) set up the Moving Pictures Expert Group (MPEG) to develop standards for the coded representation of moving pictures. In December 1988, at a meeting held at Deutsche Thomson Brandt's Hanover offices, the MPEG decided to introduce audio coding within its terms of reference.
The research on compression of music files had been carried out by a team of scientists under Prof. Karlheinz Brandenburg, working at the Fraunhofer Institute for Integrated Circuits (Fraunhofer IIS) in Bavaria. Brandenburg first built a refrigerator-size machine (!) that could reduce a sound file to 8 percent of its original size, then concentrated on replicating its effects through an algorithm.
The result was the "MPEG-1 Layer 3" algorithm described in the ISO/IEC IS 11172-3 and ISO/IEC IS 13818-3 standard documents. Its name was first shortened to "MPEG Layer 3" and later further shortened for convenience to the file suffix "mp3".
Format inventor Brandenburg worked for nearly 20 years to develop and bring to market what the world has come to know as MP3. He did not merely create a software program - he developed the very basis for perceptual audio coding technology. To create MP3, Brandenburg analysed how the human ear and brain perceive sound. The coding technique effectively fools the ear by eliminating the less essential parts of a music file. For example, if two notes are very similar, or if a high and low tone occur at exactly the same time, the brain perceives only one of them; so the MP3 algorithm selects the more important signal and discards the other. The resulting MP3 file is reduced to less than a tenth of the original size of the audio file.
MP3 Surround
The web site www.mp3surround-format.com now provides users immediate download access to free MP3 Surround evaluation software, demo samples and detailed technology information.
"The free MP3 Surround evaluation software will enable everyone to test the latest feature of the digital audio standard. We encourage music artists, engineers and producers to experience this new multi-channel audio format and realize the benefits of its portability and backward compatibility," said Henri Linde, Vice President, Growth Initiatives, Audio & MP3 program of the Intellectual Property and Licensing unit for Thomson.
The evaluation encoder enables the creation of MP3 Surround material out of five or six channel ".wav" files. The Fraunhofer IIS MP3 Surround player is capable of decoding and playing back the surround format's files as well as stereo MP3 material. This software-only solution runs on any standard PC with multi-channel audio capabilities.
Using a psychoacoustic technique called binaural cue coding, MP3 Surround captures the spatial image information of multi-channel sound. This method is critical in achieving the compact file size that MP3 users expect. The evaluation period of the MP3 Surround encoder will expire on the 31st of December 2005, while the Fraunhofer IIS player will continue to remain fully functional.
The use of the software is allowed for personal and non-commercial purposes only. Professionals can license MP3 Surround from Thomson at www.mp3licensing.com.
Full versions of MP3 Surround encoder and decoder available from www.mp3surround-format.com.