Friday, June 12, 2009

MP3 Development

MP3 audio data compression Lossy data compression algorithm uses a perceptual limitation of human hearing called auditory masking. 1894, Mayer reported that the acoustic signal is audible sound to another, less frequently. In 1959, Richard Ehmer described a complete set of auditory curves regarding this phenomenon. Terhardt Ernst et al. an algorithm describing auditory masking with high precision. This work, the authors added a series of reports dating back to Fletcher, and the work that was initially critical ratios and critical bandwidths.The psychoacoustic masking codec was the first time in 1979, apparently independently of Manfred R. Schroeder, et al . . from the ATT Bell Labs, Murray Hill, NJ, MA Krasner and in the United States of America. Krasner was the first to publish and produce speech in the hardware, not to use the music bit compression, but the publication of the results is a relatively obscure Lincoln Laboratory Technical Report no immediate impact on the development of psychoacoustic codec. Manfred Schroeder was already known figure in the global acoustic and electrical engineers, and his paper had an influence on the acoustic and source code (audio data compression) research. Both Krasner and Schroeder built upon the work by Eberhard F. Zwicker and masks the critical areas of the setting bands, which in turn to the basic research at Bell Labs is the Harvey Fletcher and his interlocutors. Large selection of (mostly perceptual) audio algorithms described IEEEs Refereed Journal Communications, optional region. The magazine reported in February 1988, a multitude of established, working audio bit compression technologies, some of them with auditory masking as part of the basic design and with multiple real-time hardware implementations aimed at laboratory experience. This hardware was never connected to the PC audio cards.The immediate predecessor, the MP3 encoding Optimal frequency (OCF) and Perceptual Transform Coding (PXFM). These two codecs, with contributions from the block-switching Thomson-Brandt, were in a codec called ASPEC, which was submitted to the MPEG and won the quality competition, but that was mistakenly rejected as too complex to implement. The first practical implementation of the Perceptual Audio Coder (OCF) in hardware (Krasner hardware was too slow and cumbersome for practical use), was the implementation of the Re-encoder based on psychoacoustic Motorola 56000 DSP chips. MP3 is directly from OCF and PXFM. MP3 is the result of collaboration between Dr. Karlheinz Brandenburg, as a postdoc at ATT Bell Labs, Mr. James D. Johnston is the ATT Bell Labs, working with the Fraunhofer Society for Integrated Circuits in Erlangen, with relatively small contributions from the MP2 branch of psychoacoustic sub-band coders.

No comments:

Post a Comment