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MPEG-1 Audio Layer 3
File name extension . A filename extension is a suffix to the name of a Computer file applied to indicate the encoding convention ( File format) of its contents mp3
Internet media type audio/mpeg
Type of format Audio

MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a digital audio encoding format using a form of lossy data compression. An Internet media type, originally called a MIME type after MIME and sometimes a Content-type after the name of a header in several protocols whose value MPEG-1 was an early Standard for Lossy compression of Video and audio. Digital audio uses Digital signals for Sound reproduction. This includes analog-to-digital conversion, digital-to-analog conversion, storage A lossy compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original but is close enough to be useful

It is a common audio format for consumer audio storage, as well as a de facto standard encoding for the transfer and playback of music on digital audio players. A de facto standard is a Standard (formal or informal that has achieved a dominant and accepted position A digital audio player, more commonly referred to as an MP3 player, is a Consumer electronics device that stores organizes and plays audio files Some

MP3 is an audio-specific format that was co-designed by several teams of engineers at Fraunhofer IIS in Erlangen, Germany, AT&T-Bell Labs in Murray Hill, NJ, USA, Thomson-Brandt, and CCETT. The Fraunhofer Society (Fraunhofer-Gesellschaft is a German research organization with 58 institutes spread throughout Germany each focusing on different fields of applied Erlangen is a Middle Franconian City in Bavaria, Germany. It is located at the confluence of the river Regnitz and its large tributary Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization It was approved as an ISO/IEC standard in 1991. The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes

MP3's use of a lossy compression algorithm is designed to greatly reduce the amount of data required to represent the audio recording and still sound like a faithful reproduction of the original uncompressed audio for most listeners, but is not considered high fidelity audio by audiophiles. A lossy compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original but is close enough to be useful For processes which reduce the amount of time it takes to listen to and understand a recording see Time-compressed speech. In Mathematics, Computing, Linguistics and related subjects an algorithm is a sequence of finite instructions often used for Calculation High fidelity or hi-fi reproduction is a term used by home stereo listeners and home audio enthusiasts ( Audiophiles to refer to high-quality reproduction An MP3 file that is created using the mid-range bitrate setting of 128 kbit/s will result in a file that is typically about 1/10th the size of the CD file created from the original audio source. In Telecommunications and Computing, bitrate (sometimes written bit rate, data rate or as a Variable R or f b Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) An MP3 file can also be constructed at higher or lower bitrates, with higher or lower resulting quality. The compression works by reducing accuracy of certain parts of sound that are deemed beyond the auditory resolution ability of most people. This method is commonly referred to as Perceptual Coding. Psychoacoustics is the study of subjective human Perception of Sounds Alternatively it can be described as the study of the Psychological correlates [1] It internally provides a representation of sound within a short term time/frequency analysis window, by using psychoacoustic models to discard or reduce precision of components less audible to human hearing, and recording the remaining information in an efficient manner. Psychoacoustics is the study of subjective human Perception of Sounds Alternatively it can be described as the study of the Psychological correlates This is relatively similar to the principles used by JPEG, an image compression format.

Contents

History

Development

The psycho-acoustic masking codec was first proposed, apparently independently in 1979, by Manfred Schroeder, et al. Auditory masking occurs when the perception of one Sound is affected by the presence of another sound (Gelfand 2004 A codec is a device or program capable of encoding and/or decoding a Digital Data stream or signal. [2] from AT&T-Bell Labs in Murray Hill, NJ, and M. Murray Hill is an unincorporated area within portions of both Berkeley Heights and New Providence, located in Union County in north-central A. Krasner[3] both in the United States. Krasner was the first to publish and to produce hardware, but the publication of his results as a relatively obscure Lincoln Laboratory Technical Report did not immediately influence the mainstream of psychoacoustic codec development. MIT Lincoln Laboratory, also known as Lincoln Lab, is a Federally funded research and development center managed by the Massachusetts Institute of Technology Manfred Schroeder was already a well known and revered figure in the world wide community of acoustical and electrical engineers and his paper had influence in acoustic and source-coding (audio compression) research. Both Krasner and Schroeder built upon the work of E. F. Zwicker [4], that in turn built on the fundamental research in the area from Bell Labs of Harvey Fletcher and his collaborators. Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization [5] A wide variety of audio compression algorithms, mostly (but not completely) perceptual were reported in a refereed journal, the Journal on Selected Areas in Communications, [6]. That journal reported in Feb. 1988 on a wide range of established, working audio bit compression technologies, most of them using auditory masking as part of their fundamental design, and several showing real-time hardware implementations.

The immediate predecessors of MP3 were "Optimum Coding in the Frequency Domain" (OCF),[7] and Perceptual Transform Coding (PXFM). [8] These two codecs, along with block-switching contributions from Thomson-Brandt, were merged into a codec called ASPEC, which was submitted to MPEG, and which won the quality competition, but that was mistakenly rejected as too complex to implement. The first practical implementation of an audio perceptual coder (OCF) in hardware (Krasner's hardware was too cumbersome and slow for practical use), was an implementation of a psychoacoustic transform coder based on Motorola 56000 DSP chips. A digital signal processor ( DSP or DSP micro) is a specialized Microprocessor designed specifically for Digital signal processing, generally MP3 is directly descended from OCF and PXFM. MP3 represents the outcome of the collaboration of Dr. Karlheinz Brandenburg, working as a PostDoc at AT&T-Bell Labs with Mr. James D. Johnston of AT&T-Bell Labs, collaborating with the Fraunhofer Society for Integrated Circuits, Erlangen, with relatively minor contributions from the MP2 branch of psychoacoustic sub-band coders.

MPEG-1 Audio Layer 2 encoding began as the Digital Audio Broadcast (DAB) project managed by Egon Meier-Engelen of the Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt (later on called Deutsches Zentrum für Luft- und Raumfahrt, German Aerospace Center) in Germany. MPEG-1 Audio Layer II ( MP2, sometimes incorrectly called Musicam) is an Audio codec defined by ISO/IEC 11172-3 Digital Audio Broadcasting ( DAB) also known as Eureka 147, is a Digital radio technology for Broadcasting Radio stations used in The German Aerospace Centre (DLR (Deutsches Zentrum für Luft- und Raumfahrt e Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. This project was financed by the European Community as a part of the EUREKA research program where it was commonly known as EU-147, which ran from 1987 to 1994. The European Community (EC is one of the Three pillars of the European Union (EU created under the Maastricht Treaty (1992 EUREKA, often abbreviated as "E!" is a pan-European Research and development funding and coordination organisation

As a doctoral student at Germany's University of Erlangen-Nuremberg, Karlheinz Brandenburg began working on digital music compression in the early 1980s, focusing on how people perceive music. History The university was founded in 1742 in Bayreuth by Frederick Margrave of Bayreuth, and moved to Erlangen in 1743 Karlheinz Brandenburg (born June 20, 1954, in Erlangen, Germany) is an Audio engineer who has contributed to the Audio compression He completed his doctoral work in 1989 and became an assistant professor at Erlangen-Nuremberg. While there, he continued to work on music compression with scientists at the Fraunhofer Society (in 1993 he joined the staff of the Fraunhofer Institute). The Fraunhofer Society (Fraunhofer-Gesellschaft is a German research organization with 58 institutes spread throughout Germany each focusing on different fields of applied [9]

In 1991, there were two proposals available: Musicam, and ASPEC - (Short excerpt on German Wikipedia) (Adaptive Spectral Perceptual Entropy Coding). MPEG-1 Audio Layer II ( MP2, sometimes incorrectly called Musicam) is an Audio codec defined by ISO/IEC 11172-3 The Musicam technique, as proposed by Philips (The Netherlands), CCETT (France) and Institut für Rundfunktechnik (Germany) was chosen due to its simplicity and error robustness, as well as its low computational power associated with the encoding of high quality compressed audio. Koninklijke Philips Electronics NV ( Royal Philips Electronics Inc. The Institut für Rundfunktechnik GmbH (IRT is the research centre of the German broadcasters ( ARD / ZDF / DLR Austria's broadcaster ( ORF) and the Swiss [10] The Musicam format, based on sub-band coding, was the basis of the MPEG Audio compression format (sampling rates, structure of frames, headers, number of samples per frame). Sub-band coding (SBC is any form of Transform coding that breaks a signal into a number of different Frequency bands and encodes each one independently Much of its technology and ideas were incorporated into the definition of ISO MPEG Audio Layer I and Layer II and the filter bank alone into Layer III (MP3) format as part of the computationally inefficient hybrid filter bank. Under the chairmanship of Professor Musmann (University of Hannover) the editing of the standard was made under the responsibilities of Leon van de Kerkhof (Layer I) and Gerhard Stoll (Layer II). The University of Hanover, officially the Gottfried Wilhelm Leibniz Universität Hannover or LUH, is a University located in Hanover,

A working group consisting of Leon van de Kerkhof (The Netherlands), Gerhard Stoll (Germany), Leonardo Chiariglione (Italy), Yves-François Dehery (France), Karlheinz Brandenburg (Germany) and James D. Working Group can mean Working group, an interdisciplinary group of researchers or Working Group (dogs, kennel club designation for Leonardo Chiariglione is an italian engineer born in Almese (in the province of Turin, Piedmont Karlheinz Brandenburg (born June 20, 1954, in Erlangen, Germany) is an Audio engineer who has contributed to the Audio compression Johnston (USA) took ideas from ASPEC, integrated the filterbank from Layer 2, added some of their own ideas and created MP3, which was designed to achieve the same quality at 128 kbit/s as MP2 at 192 kbit/s. In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission MPEG-1 Audio Layer II ( MP2, sometimes incorrectly called Musicam) is an Audio codec defined by ISO/IEC 11172-3

All algorithms were approved in 1991 and finalized in 1992 as part of MPEG-1, the first standard suite by MPEG, which resulted in the international standard ISO/IEC 11172-3, published in 1993. MPEG-1 was an early Standard for Lossy compression of Video and audio. The Moving Picture Experts Group, commonly referred to as simply MPEG, is a Working group of ISO / IEC charged with the development of video and The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes Further work on MPEG audio was finalized in 1994 as part of the second suite of MPEG standards, MPEG-2, more formally known as international standard ISO/IEC 13818-3, originally published in 1995. MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information"

Compression efficiency of encoders is typically defined by the bit rate, because compression ratio depends on the bit depth and sampling rate of the input signal. Sampling theorem The Nyquist–Shannon sampling theorem states that perfect reconstruction Nevertheless, compression ratios are often published. They may use the CD parameters as references (44. A Compact Disc (also known as a CD) is an Optical disc used to store digital data, originally developed for storing digital audio 1 kHz, 2 channels at 16 bits per channel or 2×16 bit), or sometimes the Digital Audio Tape (DAT) SP parameters (48 kHz, 2×16 bit). The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. Digital Audio Tape (DAT or R-DAT is a signal recording and playback medium developed by Sony in the mid 1980s Compression ratios with this latter reference are higher, which demonstrates the problem with use of the term compression ratio for lossy encoders.

Karlheinz Brandenburg used a CD recording of Suzanne Vega's song "Tom's Diner" to assess and refine the MP3 compression algorithm. Suzanne Nadine Vega (born 11 July 1959 in Santa Monica, California) is an American Songwriter and Singer " Tom's Diner " is an A cappella pop song written in 1981 by American Singer-songwriter Suzanne Vega. This song was chosen because of its nearly monophonic nature and wide spectral content, making it easier to hear imperfections in the compression format during playbacks. Some jokingly refer to Suzanne Vega as "The mother of MP3". Some more critical audio excerpts (glockenspiel, triangle, accordion, etc. The glockenspiel ( German, "set of bells quot or "play-bells" also known as orchestra bells and in its portable The triangle is an Idiophone type of Musical instrument in the percussion family The accordion is a portable box-shaped Musical instrument of the hand-held Bellows -driven free-reed aerophone family sometimes referred to as a Squeezebox ) were taken from the EBU V3/SQAM reference compact disc and have been used by professional sound engineers to assess the subjective quality of the MPEG Audio formats. The European Broadcasting Union ( EBU; L'Union Européenne de Radio-Télévision ("UER" and unrelated to the European Union) is a confederation It is important to understand that Suzanne Vega is recorded in an interesting fashion that results in substantial difficulties that arise due to Binaural Masking Level Depression (BMLD) as discussed in Brian C. Suzanne Nadine Vega (born 11 July 1959 in Santa Monica, California) is an American Songwriter and Singer J. Moore's book on the Psychology of Human Hearing, for instance.

Going public

A reference simulation software implementation, written in the C language and known as ISO 11172-5, was developed by the members of the ISO MPEG Audio committee in order to produce bit compliant MPEG Audio files (Layer 1, Layer 2, Layer 3). Working in non-real time on a number of operating systems, it was able to demonstrate the first real time hardware decoding (DSP based) of compressed audio. A digital signal processor ( DSP or DSP micro) is a specialized Microprocessor designed specifically for Digital signal processing, generally Some other real time implementation of MPEG Audio encoders were available for the purpose of digital broadcasting (radio DAB, television DVB) towards consumer receivers and set top boxes.

Later, on July 7, 1994 the Fraunhofer Society released the first software MP3 encoder called l3enc. Events 1456 - A retrial verdict acquits Joan of Arc of heresy 25 years after her death Year 1994 ( MCMXCIV) was a Common year starting on Saturday (link will display full 1994 Gregorian calendar) The Fraunhofer Society (Fraunhofer-Gesellschaft is a German research organization with 58 institutes spread throughout Germany each focusing on different fields of applied Fraunhofer l3enc was the first public software able to encode Wav files to the MP3 format The filename extension . A filename extension is a suffix to the name of a Computer file applied to indicate the encoding convention ( File format) of its contents mp3 was chosen by the Fraunhofer team on July 14, 1995 (previously, the files had been named . Events 1223 - Louis VIII becomes King of France upon the death of his father Philip II of France. Year 1995 ( MCMXCV) was a Common year starting on Sunday. Events of 1995 bit). With the first real-time software MP3 player Winplay3 (released September 9, 1995) many people were able to encode and play back MP3 files on their PCs. WinPlay3 is the first real-time MP3 audio player for PCs running Windows, both 16-bit (Windows 3 Events 1000 - Battle of Svolder, Viking Age. 1379 - Treaty of Neuberg, splitting the Austrian Year 1995 ( MCMXCV) was a Common year starting on Sunday. Events of 1995 Because of the relatively small hard drives back in that time (~ 500 MB) lossy compression was essential to store non-instrument based (see tracker and MIDI) music for playback on a computer. A hard disk drive ( HDD) commonly referred to as a hard drive, hard disk, or fixed disk drive, is a Non-volatile storage device A megabyte is a unit of Information or Computer storage equal to either 106 (1000000 Bytes or 220 (1048576 bytes depending on Tracker is the generic term for a class of software Music sequencers which in their purest form allow the user to arrange sound samples stepwise on a timeline across MIDI ( Musical Instrument Digital Interface, ˈmɪdi is an industry-standard protocol that enables Electronic musical instruments Computers

Internet

From the first half of 1995 through the late 1990s, MP3 files began to spread on the Internet. The Internet is a global system of interconnected Computer networks MP3's popularity began to rise rapidly with the advent of Nullsoft's audio player Winamp (released in 1997), and the Unix audio player mpg123. Nullsoft Inc is a Software house founded in 1997 by Justin Frankel. Winamp is a proprietary media player written by Nullsoft, now a subsidiary of Time Warner. mpg123 is a fast free, minimalist, console MPEG audio player software program for UNIX and Linux Operating systems The small size of MP3 files has enabled widespread peer-to-peer file sharing of music ripped from compact discs, which would previously have been nearly impossible. For other uses of the term see Peer-to-peer (disambiguation For peer-to-peer networks used for file sharing see File sharing See Shared resource for the conventional meaning of file sharing File sharing refers to the providing and receiving of digital files over a Ripping is the process of copying audio or video content to a Hard disk, typically from Removable media or media streams. A Compact Disc (also known as a CD) is an Optical disc used to store digital data, originally developed for storing digital audio The first large peer-to-peer filesharing network, Napster, was released in 1999. Napster was an online music file sharing service created by Shawn Fanning while he was attending Northeastern University in Boston and operating

The ease of creating and sharing MP3s resulted in widespread copyright infringement. Copyright is a legal concept enacted by Governments, giving the creator of an original work of authorship Exclusive rights to control its distribution usually for Major record companies argue that this free sharing of music reduces sales, and call it "music piracy". 'Copyright infringement' (or copyright violation) is the unauthorized use of material that is covered by Copyright law in a manner that violates They reacted by pursuing lawsuits against Napster (which was eventually shut down) and eventually against individual users who engaged in file sharing.

Despite the popularity of MP3, online music retailers often use other proprietary formats that are encrypted (known as Digital rights management) to prevent users from using purchased music in ways not specifically authorized by the record companies. Digital rights management ( DRM) is a generic term that refers to Access control technologies used by hardware manufacturers publishers and Copyright holders The record companies argue that this is necessary to prevent the files from being made available on peer-to-peer file sharing networks. However, this has other side effects such as preventing users from playing back their purchased music on different types of devices. The audio content of these files can be converted into an unencrypted format, however, because often the user permissions include "burn to audio CD". Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) And even when that option is not available, many sound cards allow the user to record anything they play. A sound card (also known as an audio card is a Computer Expansion card that facilitates the input and output of audio signals to/from a computer under Unauthorized MP3 filesharing continues on next-generation peer-to-peer networks, though some authorized services, such as eMusic, and Amazon.com sell unrestricted music in the MP3 format. eMusic is an Online music store that operates by Subscription. Amazoncom Inc ( is an American electronic commerce ( E-commerce) company in Seattle Washington.

Encoding audio

The MPEG-1 standard does not include a precise specification for an MP3 encoder. MPEG-1 was an early Standard for Lossy compression of Video and audio. Implementers of the standard were supposed to devise their own algorithms suitable for removing parts of the information in the raw audio (or rather its MDCT representation in the frequency domain). The modified discrete cosine transform (MDCT is a Fourier-related transform based on the type-IV Discrete cosine transform (DCT-IV with the additional property During encoding, 576 time domain samples are taken and are transformed to 576 frequency domain samples. If there is a transient, 192 samples are taken instead of 576. In Acoustics and Audio, a transient is a short-duration Signal that represents a non-harmonic attack phase of a musical sound or spoken word This is done to limit the temporal spread of quantization noise accompanying the transient. (See psychoacoustics. Psychoacoustics is the study of subjective human Perception of Sounds Alternatively it can be described as the study of the Psychological correlates )

As a result, there are many different MP3 encoders available, each producing files of differing quality. Comparisons are widely available, so it is easy for a prospective user of an encoder to research the best choice. It must be kept in mind that an encoder that is proficient at encoding at higher bit rates (such as LAME) is not necessarily as good at lower bit rates. LAME is an Open source application used to encode audio into the MP3 file format

Decoding audio

Decoding, on the other hand, is carefully defined in the standard. Most decoders are "bitstream compliant", which means that the decompressed output - that they produce from a given MP3 file - will be the same (within a specified degree of rounding tolerance) as the output specified mathematically in the ISO/IEC standard document. For the drum and bass musician see Decoder (artist A decoder is a device which does the reverse of an Encoder, undoing the An elementary stream (ES as defined by MPEG communication protocol is usually the output of an audio or video Encoder. For lip-rounding in phonetics see Labialisation and Roundedness. The MP3 file has a standard format, which is a frame that consists of 384, 576, or 1152 samples (depends on MPEG version and layer), and all the frames have associated header information (32 bits) and side information (9, 17, or 32 bytes, depending on MPEG version and stereo/mono). The header and side information help the decoder to decode the associated Huffman encoded data correctly. History In 1951 David A Huffman and his MIT information theory classmates were given

Therefore, comparison of decoders is usually based on how computationally efficient they are (i. e. , how much memory or CPU time they use in the decoding process).

Audio quality

When performing lossy audio encoding, such as creating an MP3 file, there is a trade-off between the amount of space used and the sound quality of the result. Typically, the creator is allowed to set a bit rate, which specifies how many kilobits the file may use per second of audio, for example, when ripping a compact disc to this format. In Telecommunications and Computing, bitrate (sometimes written bit rate, data rate or as a Variable R or f b A kilobit is a unit of information abbreviated kbit (or kb) The standard definition is 1 kilobit = 103 bit = 1000 Bit. Ripping is the process of copying audio or video content to a Hard disk, typically from Removable media or media streams. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) The lower the bit rate used, the lower the audio quality will be, but the smaller the file size. Likewise, the higher the bit rate used, the higher the quality, and therefore, larger the resulting file will be.

Files encoded with a lower bit rate will generally play back at a lower quality. With too low a bit rate, "compression artifacts" (i. A compression artifact (or artefact) is the result of an aggressive Data compression scheme applied to an Image, audio, or Video e. , sounds that were not present in the original recording) may be audible in the reproduction. Some audio is hard to compress because of its randomness and sharp attacks. When this type of audio is compressed, artifacts such as ringing or pre-echo are usually heard. Pre-echo is an audio Compression artifact where a sound is heard before it occurs (hence the name A sample of applause compressed with a relatively low bitrate provides a good example of compression artifacts.

Besides the bit rate of an encoded piece of audio, the quality of MP3 files also depends on the quality of the encoder itself, and the difficulty of the signal being encoded. As the MP3 standard allows quite a bit of freedom with encoding algorithms, different encoders may feature quite different quality, even when targeting similar bit rates. As an example, in a public listening test featuring two different MP3 encoders at about 128 kbit/s,[11] one scored 3. 66 on a 1–5 scale, while the other scored only 2. 22.

Quality is heavily dependent on the choice of encoder and encoding parameters. While quality around 128 kbit/s was somewhere between annoying and acceptable with older encoders, modern MP3 encoders can provide adequate quality at those bit rates[12] (January 2006). However, in 1998, MP3 at 128 kbit/s was only providing quality equivalent to AAC-LC at 96 kbit/s and MP2 at 192 kbit/s. [13]

The transparency threshold of MP3 can be estimated to be at about 128 kbit/s with good encoders on typical music as evidenced by its strong performance in the above test, however some particularly difficult material, or music encoded for the use of people with more sensitive hearing can require 192 kbit/s or higher. In Data compression or Psychoacoustics, transparency is the ideal result of Lossy data compression. As with all lossy formats, some samples cannot be encoded to be transparent for all users.

The simplest type of MP3 file uses one bit rate for the entire file — this is known as Constant Bit Rate (CBR) encoding. Constant bitrate (CBR is a term used in Telecommunications, relating to the Quality of service. Using a constant bit rate makes encoding simpler and faster. However, it is also possible to create files where the bit rate changes throughout the file. These are known as Variable Bit Rate (VBR) files. Variable bitrate ( VBR) or less commonly variable bit rate, is a term used in Telecommunications and Computing that relates to the The idea behind this is that, in any piece of audio, some parts will be much easier to compress, such as silence or music containing only a few instruments, while others will be more difficult to compress. So, the overall quality of the file may be increased by using a lower bit rate for the less complex passages and a higher one for the more complex parts. With some encoders, it is possible to specify a given quality, and the encoder will vary the bit rate accordingly. Users who know a particular "quality setting" that is transparent to their ears can use this value when encoding all of their music, and not need to worry about performing personal listening tests on each piece of music to determine the correct settings.

In a listening test, MP3 encoders at low bit rates performed significantly worse than those using more modern compression methods (such as AAC). In a 2004 public listening test at 32 kbit/s,[14] the LAME MP3 encoder scored only 1. 79/5 — behind all modern encoders — with Nero Digital HE AAC scoring 3. Nero Digital is a brand name applied to a suite of MPEG-4 -compatible video and audio compression Codecs developed by Nero AG of Germany and 30/5.

Perceived quality can be influenced by listening environment (ambient noise), listener attention, and listener training and in most cases by listener audio equipment (such as sound cards, speakers and headphones).

Bit rate

Several bit rates are specified in the MPEG-1 Layer 3 standard: 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 192, 224, 256 and 320 kbit/s, and the available sampling frequencies are 32, 44. Sampling theorem The Nyquist–Shannon sampling theorem states that perfect reconstruction 1 and 48 kHz. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. A sample rate of 44. 1 kHz is almost always used, because this is also used for CD audio, the main source used for creating MP3 files. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) A greater variety of bit rates are used on the Internet. 128 kbit/s is the most common, because it typically offers adequate audio quality in a relatively small space. 192 kbit/s is often used by those who notice artifacts at lower bit rates. As the Internet bandwidth availability and hard drive sizes have increased, 128 kbit/s bitrate files are slowly being replaced with higher bitrates like 192 kbit/s, with some being encoded up to MP3's maximum of 320 kbit/s. In Computer networking and Computer science, digital bandwidth or just bandwidth is the capacity for a given system to transfer data over a connection It is unlikely that higher bit rates will be popular with any lossy audio codec as higher bit rates than 320 kbit/s encroach on the domain of lossless codecs such as FLAC. A lossy compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original but is close enough to be useful Lossless data compression is a class of Data compression Algorithms that allows the exact original data to be reconstructed from the compressed data Free Lossless Audio Codec ( FLAC) is a File format for lossless Audio data compression.

By contrast, uncompressed audio as stored on a compact disc has a bit rate of 1,411. A Compact Disc (also known as a CD) is an Optical disc used to store digital data, originally developed for storing digital audio 2 kbit/s (16 bits/sample × 44100 samples/second × 2 channels / 1000 bits/kilobit).

Some additional bit rates and sample rates were made available in the MPEG-2 and the (unofficial) MPEG-2. 5 standards: bit rates of 8, 16, 24, and 144 kbit/s and sample rates of 8, 11. 025, 12, 16, 22. 05 and 24 kHz.

Non-standard bit rates up to 640 kbit/s can be achieved with the LAME encoder and the freeformat option, although few MP3 players can play those files. LAME is an Open source application used to encode audio into the MP3 file format According to the ISO standard, decoders are only required to be able to decode streams up to 320 kbit/s. [15]

File structure

An MP3 file is made up of multiple MP3 frames, which consist of the MP3 header and the MP3 data. This sequence of frames is called an Elementary stream. An elementary stream (ES as defined by MPEG communication protocol is usually the output of an audio or video Encoder. Frames are not independent items ("byte reservoir") and therefore cannot be extracted on arbitrary frame boundaries. The MP3 data is the actual audio payload. The diagram shows that the MP3 header consists of a sync word, which is used to identify the beginning of a valid frame. In computing a syncword is used to synchronize data For example an audio receiver is receiving a bit stream of data This is followed by a bit indicating that this is the MPEG standard and two bits that indicate that layer 3 is used; hence MPEG-1 Audio Layer 3 or MP3. The Moving Picture Experts Group, commonly referred to as simply MPEG, is a Working group of ISO / IEC charged with the development of video and After this, the values will differ, depending on the MP3 file. ISO/IEC 11172-3 defines the range of values for each section of the header along with the specification of the header. The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes Most MP3 files today contain ID3 metadata, which precedes or follows the MP3 frames; this is also shown in the diagram. ID3 is a Metadata container most often used in conjunction with the MP3 Audio file format. Metadata ( meta data, or sometimes metainformation) is "data about data" of any sort in any media

Design limitations

There are several limitations inherent to the MP3 format that cannot be overcome by any MP3 encoder. Newer audio compression formats such as Vorbis, WMA Pro and AAC no longer have these limitations. Vorbis is a free and open source, lossy audio Codec project headed by the Xiph Windows Media Audio ( WMA) is an Audio data compression technology developed by Microsoft. Advanced Audio Coding ( AAC) is a standardized lossy compression and encoding scheme for Digital audio. In technical terms, MP3 is limited in the following ways:

ID3 and other tags

Main articles: ID3 and APEv2 tag

A "tag" in a compressed audio file is a section of the file that contains metadata such as the title, artist, album, track number or other information about the file's contents. ID3 is a Metadata container most often used in conjunction with the MP3 Audio file format. Metadata ( meta data, or sometimes metainformation) is "data about data" of any sort in any media

As of 2006, the most widespread standard tag formats are ID3v1 and ID3v2, and the more recently introduced APEv2. ID3 is a Metadata container most often used in conjunction with the MP3 Audio file format.

APEv2 was originally developed for the MPC file format (see the APEv2 specification). Musepack or MPC is an Open source lossy audio codec, specifically optimized for transparent compression of stereo audio at bitrates of 160&ndash180 APEv2 can coexist with ID3 tags in the same file or it can be used by itself.

Tag editing functionality is often built-in to MP3 players and editors, but there also exist tag editors dedicated to the purpose (see filerename.co.uk for a free open source example). A tag editor (or tagger) is a piece of Software that supports editing Metadata of Multimedia File formats rather than the actual file

Volume normalization

As compact discs and other various sources are recorded and mastered at different volumes, it may be useful to store volume information about a file in the tag so that at playback time, the volume can be dynamically adjusted. A Compact Disc (also known as a CD) is an Optical disc used to store digital data, originally developed for storing digital audio

A few standards for encoding the gain of an MP3 file have been proposed. The idea is to normalize the average volume (not the volume peaks) of audio files, so that the volume does not change between consecutive tracks. This should not be confused with dynamic range compression (DRC), which is a form of normalization used in audio mastering. Dynamic range compression, also called DRC (often seen in DVD player settings or simply compression, is a process that reduces the Dynamic range of Audio normalization is the process of increasing (or decreasing the Amplitude of an Audio signal

Listeners who prefer to experience music as it was intended to be heard on the original compact disc may prefer to not use volume normalization, because the average volume of each track was set intentionally by a professional mastering engineer. Audio normalization is the process of increasing (or decreasing the Amplitude of an Audio signal

One of the most popular and widely used solution for storing replay gain is known simply as "Replay Gain". Replay Gain is a proposed standard published in 2001 to normalize the perceived Loudness of computer audio formats such as MP3 and Typically, the average volume and clipping information about the audio track is stored in its metadata tag.

Licensing and patent issues

A large number of different organizations have claimed ownership of patents necessary to implement MP3 (decoding and/or encoding). These different claims have led to a number of legal actions, and legal threats, from a variety of sources, resulting in uncertainty about what is necessary to legally create products with MP3 support in countries where those patents are valid.

The various patents claimed to cover MP3 by different patent-holders have many different expiration dates, ranging from 2007 to 2017 in the U. S. [16]

Thomson Consumer Electronics claims to control MP3 licensing of the MPEG-1/2 Layer 3 patents in many countries, including the United States, Japan, Canada and EU countries. Thomson SA (,) formerly known as Thomson Multimedia is an international provider of solutions for the creation management delivery and access of video for the The United States of America —commonly referred to as the For a topic outline on this subject see List of basic Japan topics. Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page [17] Thomson has been actively enforcing these patents.

For current information about Fraunhofer IIS and Thomson's patent portfolio and licensing terms and fees see their website mp3licensing.com. The Fraunhofer Society (Fraunhofer-Gesellschaft is a German research organization with 58 institutes spread throughout Germany each focusing on different fields of applied A patent portfolio is a collection of Patents owned by a single entity such as an individual or Corporation. MP3 license revenues generated ca. 100 million Euro revenue to the Fraunhofer Society in 2005. [18]

In September 1998, the Fraunhofer Institute sent a letter to several developers of MP3 software stating that a license was required to "distribute and/or sell decoders and/or encoders". The letter claimed that unlicensed products "infringe the patent rights of Fraunhofer and THOMSON. To make, sell and/or distribute products using the [MPEG Layer-3] standard and thus our patents, you need to obtain a license under these patents from us. "[19]

These patent issues significantly slowed the development of unlicensed MP3 software and led to increased focus on creating and popularizing alternatives such as Vorbis, AAC, and WMA. Vorbis is a free and open source, lossy audio Codec project headed by the Xiph Advanced Audio Coding ( AAC) is a standardized lossy compression and encoding scheme for Digital audio. Windows Media Audio ( WMA) is an Audio data compression technology developed by Microsoft. Microsoft chose to move away from MP3 to its own proprietary Windows Media format to avoid licensing issues associated with these patents. Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer Windows Media is a Multimedia framework for media creation and distribution for Microsoft Windows. Until the key patents expire, unlicensed encoders and players could be infringing in countries where the patents are valid. Patent infringement is the act of utilizing a patented Invention without permission from the Patent holder

In spite of the patent restrictions, the perpetuation of the MP3 format continues. The reasons for this appear to be the network effects caused by:

Additionally, patent holders declined to enforce license fees on free and open source decoders, which allows many free MP3 decoders to develop. Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified Open source is a development methodology which offers practical accessibility to a product's source (goods and knowledge [20] Furthermore, while attempts have been made to discourage distribution of encoder binaries, Thomson has stated that individuals who use free MP3 encoders are not required to pay fees. Thus, while patent fees have been an issue for companies that attempt to use MP3, they have not meaningfully impacted users, which allows the format to grow in popularity.

Sisvel S.p.A. and its U. S. subsidiary Audio MPEG, Inc. previously sued Thomson for patent infringement on MP3 technology,[21] but those disputes were resolved in November 2005 with Sisvel granting Thomson a license to their patents. Motorola also recently signed with Audio MPEG to license MP3-related patents.

In September 2006 German officials seized MP3 players from SanDisk's booth at the IFA show in Berlin after an Italian patents firm won an injunction on behalf of Sisvel against SanDisk in a dispute over licencing rights. SanDisk Corporation ( is an American Multinational corporation which designs and markets Flash memory card products The IFA or Internationale Funkausstellung Berlin (International radio exhibition Berlin) is one of the oldest Industrial exhibitions in Germany The injunction was later reversed by a Berlin judge;[22] but that reversal was in turn blocked the same day by another judge from the same court, "bringing the Patent Wild West to Germany" in the words of one commentator. [23]

On February 16, 2007, Texas MP3 Technologies sued Apple, Samsung Electronics and Sandisk with a patent-infringement lawsuit regarding portable MP3 players. Events 1249 - Andrew of Longjumeau is dispatched by Louis IX of France as his ambassador to meet with the Khan of the Mongols Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. The suit was filed in Marshall, Texas; this is a common location for patent infringement suits due to speedy trials. The United States District Court for the Eastern District of Texas is the Federal district court with jurisdiction over the eastern part of Texas and is a part of Texas MP3 Technologies claimed infringement with U. S. patent 7,065,417, awarded in June 2006 to multimedia chip-maker SigmaTel, covering "an MPEG portable sound reproducing system and a method for reproducing sound data compressed using the MPEG method. "[24]

Alcatel-Lucent also claims ownership of several patents relating to MP3 encoding and compression, inherited from AT&T-Bell Labs. Alcatel-Lucent is one of the world's biggest industry players in Telecommunications that provides hardware software and services to Service Providers Enterprises and In November 2006, (prior to the companies' merger) Alcatel filed a lawsuit against Microsoft (see Alcatel-Lucent v. Microsoft), alleging infringement of seven of its patents. Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer Origin of the cases The dispute between Microsoft and Lucent (and later Alcatel-Lucent began in 2003 when Lucent Technologies (acquired On February 23, 2007 a San Diego court upheld the suit, and awarded Alcatel-Lucent a record-breaking US$1. Events 1455 - Traditional date for the publication of the Gutenberg Bible, the first Western Book printed from Movable Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Alcatel-Lucent is one of the world's biggest industry players in Telecommunications that provides hardware software and services to Service Providers Enterprises and 52 billion in damages. [25] Microsoft has said it will appeal the verdict, maintaining that the federal jury's decision is "unsupported by the law or facts", since Microsoft had already paid US$16 million to license the technology from Fraunhofer IIS, which, it claims, is "the industry-recognized rightful licensor". Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer The Fraunhofer Society (Fraunhofer-Gesellschaft is a German research organization with 58 institutes spread throughout Germany each focusing on different fields of applied [26] A week later on March 2, U. Events 986 - Louis V becomes King of the Franks. 1127 - Assassination of Charles the Good S. District Judge Rudi Brewster ruled from the bench in a related suit and dismissed all of Alcatel-Lucent's patents claims relating to speech recognition. Alcatel-Lucent plans to appeal the ruling. [27]

In short, with Thomson, Fraunhofer IIS, Sisvel (and its U. S. subsidiary Audio MPEG), Texas MP3 Technologies, and Alcatel-Lucent all claiming legal control of relevant MP3 patents related to decoders, the legal status of MP3 remains unclear in countries where those patents are valid.

Alternative technologies

Main article: List of codecs

Many other lossy and lossless audio codecs exist. Alcatel-Lucent is one of the world's biggest industry players in Telecommunications that provides hardware software and services to Service Providers Enterprises and The Fraunhofer Society (Fraunhofer-Gesellschaft is a German research organization with 58 institutes spread throughout Germany each focusing on different fields of applied The following is a list of Codecs Audio codecs See also Audio codec Non-compression formats Audio Interchange File Format A codec is a device or program capable of encoding and/or decoding a Digital Data stream or signal. Among these, mp3PRO, AAC, and MP2 are all members of the same technological family as MP3 and depend on roughly similar psychoacoustic models. mp3PRO is an Audio compression algorithm (or Codec) that combines the MP3 audio format with Spectral band replication compression methods Advanced Audio Coding ( AAC) is a standardized lossy compression and encoding scheme for Digital audio. Psychoacoustics is the study of subjective human Perception of Sounds Alternatively it can be described as the study of the Psychological correlates The Fraunhofer Gesellschaft owns many of the basic patents underlying these codecs as well, with others held by Dolby Labs, Sony, Thomson Consumer Electronics, and AT&T. The Fraunhofer Society (Fraunhofer-Gesellschaft is a German research organization with 58 institutes spread throughout Germany each focusing on different fields of applied A patent is a set of Exclusive rights granted by a State to an inventor or his assignee for a fixed period of time in exchange for a disclosure of an is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with Thomson SA (,) formerly known as Thomson Multimedia is an international provider of solutions for the creation management delivery and access of video for the Before proposing a merge request please see Talk and see if the merger you propose has recently been made and

See also

References

  1. ^ Jayant, N. For processes which reduce the amount of time it takes to listen to and understand a recording see Time-compressed speech. The following tables compare general and technical information for a variety of Audio codecs For Listening tests comparing the perceived audio quality of audio codecs see the 'Copyright infringement' (or copyright violation) is the unauthorized use of material that is covered by Copyright law in a manner that violates A digital audio player, more commonly referred to as an MP3 player, is a Consumer electronics device that stores organizes and plays audio files Some ID3 is a Metadata container most often used in conjunction with the MP3 Audio file format. In Audio engineering, joint refers to a joining of several channels of similar information in order to obtain higher quality or smaller file size LRC is a Computer file format that synchronizes song Lyrics with an audio file such as MP3, Vorbis or MIDI. Media Player was a media player originally included in Windows 3 An MP3 blog is a type of Blog in which the creator makes music files normally in the MP3 format available for download MP3 Surround is a type of MP3 that supports 51 channels of audio Streaming multimedia is Multimedia that is constantly received by and normally presented to an end-user while it is being delivered by a streaming provider (the DJ digital controllers are MIDI controllers for playing computer based music tracks normally at clubs or events Advanced Audio Coding ( AAC) is a standardized lossy compression and encoding scheme for Digital audio. Vorbis is a free and open source, lossy audio Codec project headed by the Xiph S. , Johnston, J. D. and Safranek, R. J. (1993–10). "Signal compression based on models of human perception". . Proc. IEEE, Oct. 1993, pp. 1385-1422
  2. ^ "Optimizing Digital Speech Coding by Exploiting Masking Properties of the Human Ear"; M. R. Schroeder, B. S. Atal and J. L. Hall; J. Acoust. Soc. Am. ; received 8 June 1979; accepted for publication 13 August 1979; Dec. 1979
  3. ^ "Digital Encoding of Speech and Audio Signals Based on the Perceptual Requirements of the Auditory System"; M. A. Krasner; Massachusetts Institute of Technology Lincoln Laboratory Technical Report 535; 18 June 1979
  4. ^ "On the Psycho-acoustical Equivalent of Tuning Curves"; E. F. Zwicker; Proceedings of the Symposium on Psychophysical Models and Physiological Facts in Hearing; held at Tuzing, Oberbayern, April 22–26, 1974
  5. ^ "The ASA Edition of Speech and Hearing in Communication", edited by J. B. Allen, Acoustical Society of America, reprinted in 1995
  6. ^ IEEE Jour. Selected Areas in Commun. , vol. 6, no. 2, Feb 1988
  7. ^ K. Brandenburg, D. Seitzer; Universitaet Erlangen-Nuernberg, Erlangen (November 3–6 1988). "OCF: Coding High Quality Audio with Data Rates of 64 KBit/sec". . Audio Engineering Society, 85th Convention
  8. ^ Johnston, J. D. , “Transform coding of audio signals using perceptual noise criteria,” IEEE Jour. Selected Areas in Commun. , vol. 6, no. 2, Feb 1988, pp. 314-323
  9. ^ Jack Ewing (March 5, 2007). How MP3 Was Born. BusinessWeek. com. Retrieved on 2007-07-24. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1132 - Battle of Nocera between Ranulf II of Alife and Roger II of Sicily.
  10. ^ Press Release - Status report of ISO MPEG
  11. ^ [|Amorim, Roberto] (2003-08-03), Results of 128 kbit/s Extension Public Listening Test, <http://www.rjamorim.com/test/128extension/results.html>. Retrieved on 17 March 2007 
  12. ^ [|Mares, Sebastian] (2006–01), Results of Public, Multiformat Listening Test @ 128 kbit/s, <http://www.listening-tests.info/mf-128-1/results.htm>. Retrieved on 17 March 2007 
  13. ^ David Meares, Kaoru Watanabe & Eric Scheirer (1998–02). "Report on the MPEG-2 AAC Stereo Verification Tests" (PDF). . International Organisation for Standardisation Retrieved on 2007-03-17. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 45 BC - In his last victory Julius Caesar defeats the Pompeian forces of Titus Labienus and Pompey the Younger
  14. ^ [|Amorim, Roberto] (2004-07-11), Results of Dial-up bit rate public Listening Test, <http://www.rjamorim.com/test/32kbps/results.html>. Retrieved on 17 March 2007 
  15. ^ [|Bouvigne, Gabriel] (2006-11-28), freeformat at 640 kbit/s and foobar2000, possibilities?, <http://www.hydrogenaudio.org/forums/index.php?s=&showtopic=38808&view=findpost&p=452751>. Retrieved on 17 March 2007 
  16. ^ tunequest (2007-02-26). Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 747 BC - Epoch (origin of Ptolemy 's Nabonassar Era 364 - Valentinian I is proclaimed Big List of MP3 Patents (and supposed expiration dates).
  17. ^ Acoustic Data Compression -- MP3 Base Patent. Foundation for a Free Information Infrastructure (January 15, 2005). Retrieved on 2007-07-24. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1132 - Battle of Nocera between Ranulf II of Alife and Roger II of Sicily.
  18. ^ Muzinée Kistenfeger (May, 2006). The Fraunhofer Society (Fraunhofer-Gesellschaft, FhG). British Consulate-General Munich. Retrieved on 2007-07-24. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1132 - Battle of Nocera between Ranulf II of Alife and Roger II of Sicily.
  19. ^ Early MP3 Patent Enforcement. Chilling Effects Clearinghouse (September 1, 1998). Retrieved on 2007-07-24. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1132 - Battle of Nocera between Ranulf II of Alife and Roger II of Sicily.
  20. ^ Glyn Moody (June 15, 2007). Should We Fight for Ogg Vorbis? (Internet Archive copy). The Internet Archive ( IA) is a Nonprofit organization dedicated to maintaining an on-line Library and archive of Web and Linux Journal. Linux Journal is a monthly Magazine published by Belltown Media Inc Retrieved on 2008-04-06. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 46 BC - Julius Caesar defeats Caecilius Metellus Scipio and Marcus Porcius Cato in the Battle of Thapsus
  21. ^ Audio MPEG and Sisvel: Thomson sued for patent infringement in Europe and the United States - MP3 players stopped by customs. ZDNet India (October 6, 2005). Retrieved on 2007-07-24. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1132 - Battle of Nocera between Ranulf II of Alife and Roger II of Sicily.
  22. ^ Erica Ogg (September 7, 2006). SanDisk MP3 seizure order overturned. CNET News. com. Retrieved on 2007-07-24. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1132 - Battle of Nocera between Ranulf II of Alife and Roger II of Sicily.
  23. ^ Sisvel brings Patent Wild West into Germany. IPEG blog (September 7, 2006). Retrieved on 2007-07-24. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1132 - Battle of Nocera between Ranulf II of Alife and Roger II of Sicily.
  24. ^ Martyn Williams (2007-02-26). Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 747 BC - Epoch (origin of Ptolemy 's Nabonassar Era 364 - Valentinian I is proclaimed Texas MP3 Technologies claims the companies infringed its patent covering 'an MPEG portable sound reproducing system'. IDG News Service.
  25. ^ BBC report of the Alcatel-Lucent lawsuit verdict: Microsoft faces $1.5bn MP3 payout (February 22, 2007). Retrieved on 2007-07-24. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1132 - Battle of Nocera between Ranulf II of Alife and Roger II of Sicily.
  26. ^ Joe Wilcox (2007-02-23). Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1455 - Traditional date for the publication of the Gutenberg Bible, the first Western Book printed from Movable Microsoft's Patent Disputes with Alcatel-Lucent, AT&T Make Waves.
  27. ^ Anne Broache (2007-03-02). Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 986 - Louis V becomes King of the Franks. 1127 - Assassination of Charles the Good Microsoft wins in second Alcatel-Lucent patent suit. CNET News. com, published on ZDNet news.

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