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Aportable media player (PMP) ordigital audio player (DAP) is a portableconsumer electronics device capable of storing and playingdigital media such as audio, images, and video files.[1][2] Normally they refer to small,battery-powered devices utilisingflash memory or ahard disk for storing various mediafiles.[3][4]MP3 players has been a popular alternative name used for such devices, even if they also support otherfile formats and media types other thanMP3 (for exampleAAC,FLAC,WMA).[5][6]
Generally speaking, PMPs are equipped with a 3.5 mmheadphone jack which can be used forheadphones or to connect to aboombox,home audio system, or connect tocar audio and homestereos wired or via a wireless connection such asBluetooth, and some may includeradio tuners,voice recording and other features. In contrast, analogueportable audio players play music from non-digital media that useanalogue media, such ascassette tapes orvinyl records. As devices became more advanced, the PMP term was later introduced to describe players with additional capabilities such asvideo playback (they used to also be called "MP4 players"). The PMP term has also been used as an umbrella name to describe any portable device for multimedia, including physical formats (such asportable CD players) orhandheld game consoles with such capabilities.[7][8]
DAPs appeared in the late 1990s, following the creation of the MP3 codec in Germany. MP3-playing devices were mostly pioneered bySouth Korean startups, who by 2002 would control the majority of global sales.[9] However the industry would eventually be defined by the popularApple iPod.[10] In 2006, 20% of Americans owned a PMP, a figure strongly driven by the young; more than half (54%) of American teens owned one, as did 30% of young adults aged 18 to 34.[11] In 2007, 210 million PMPs were sold worldwide, worth US$19.5 billion.[12] In 2008, video-enabled players would overtake audio-only players.[13] Increasing sales ofsmartphones andtablet computers have led to a decline in sales of PMPs,[14][15] leading to most manufacturers having exited the industry during the 2010s.Sony Walkman continues to be in production andportable DVD and BD players, which may be considered variations of PMPs, are still manufactured.[16]
The term portable media player (PMP) generally refers to (but not limited to) playback ofdigital audio files rather than directly on tape or disc.
As of 2025[update], PMPs tend to store such files on internalflash memory or removableflash memory cards, both of which are (along withUSB flash drives) non-mechanicalsolid state devices. Due to technological advances in flash memory, these originally low-capacity storage devices are now available commercially, ranging up to high storage capacities. Because they are solid state and do not have moving parts, they require less battery power, will not skip during playback, and may be more resilient to hazards such asmechanical shock orfragmentation than hard disk drive-based players.
As recently as 2010,hard disk drive based players were common. At the time, these players had capacities ranging up to 500 GB.[17] At typical encoding rates, this means that tens of thousands of songs can be stored on one player. The disadvantages with these units is that a hard drive consumes more power, is larger and heavier and is inherently more fragile than solid-state storage.
Portable CD players that can decode and play MP3 audio files stored on CDROMs (MP3 CDs) are also effectively MP3 players. When the first units of these were released, such players were typically a less expensive alternative than either the hard drive or flash-based players. The blankCD-R media they use is inexpensive. These devices have the feature of being able to play standardaudio CDs. Since a CD can typically hold only around 700 megabytes of data, a large library will typically require multiple discs. However, some higher-end units are also capable of reading and playing back files stored on larger-capacityDVD; some also have the ability to play video content, such as movies.
Players that connect via (Wi-Fi) network to receive and play audio can also be considered PMPs.[18] These units typically do not have significant local storage and must rely on a server, typically a personal computer also on the samenetwork, to provide the audio files for playback.Smartphones can also be considered PMPs as they have most of the media functions of a typical PMP.
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Digital sampling is used to convert an audio wave to a sequence of binary numbers that can be stored in a digital format, such as MP3. Common features of all MP3 players are a memory storage device, such as flash memory or a miniature hard disk drive, anembedded processor, and an audiocodec microchip to convert the compressed file into an analogue sound signal. During playback, audio files are read from storage into aRAM based memory buffer, and then streamed through an audio codec to produce decodedPCM audio. Typically audio formats decode at double to more than 20 times real speed on portable electronicprocessors,[19] requiring that the codec output be stored for a time until theDAC can play it. To save power, portable devices may spend much or nearly all of their time in a low power idle state while waiting for the DAC to deplete the output PCM buffer before briefly powering up to decode additional audio.
Most DAPs are powered byrechargeable batteries, some of which are not user-replaceable. They have a 3.5 mm stereo jack; music can be listened to withearbuds orheadphones, or played via an external amplifier andspeakers. Some devices also contain internal speakers, through which music can be listened to, although these built-in speakers are typically of very low quality.
Nearly all DAPs consists of some kind of display screen, although there are exceptions, such as theiPod Shuffle, and a set of controls with which the user can browse through the library of music contained in the device, select a track, and play it back. The display, if the unit even has one, can be anything from a simple one or two line monochromeLCD display, similar to what are found on typicalpocket calculators, to large, high-resolution, full-color displays capable of displaying photographs or viewing video content on. The controls can range anywhere from the simple buttons as are found on most typicalCD players, such as for skipping through tracks or stopping/starting playback to full touch-screen controls, such as that found on theiPod Touch or theZune HD. One of the more common methods of control is some type of thescroll wheel with associated buttons. This method of control was first introduced with the Apple iPod and many other manufacturers have created variants of this control scheme for their respective devices.
A standard PMP uses a 5-wayD-pad to navigate. Many alternatives have been used, most notably the wheel and touch mechanisms seen on players from theiPod andSansa series. Another popular mechanism is the swipe-pad, or 'squircle', first seen on theZune. Additional buttons are commonly seen for features such as volume control.
Content is placed on DAPs typically through a process called "syncing", by connecting the device to a personal computer, typically viaUSB, and running any special software that is often provided with the DAP on aCD-ROM included with the device, or downloaded from the manufacturer's website. Some devices simply appear as an additional disk drive on the host computer, to which music files are simply copied like any other type of file. Other devices, most notably the Apple iPod or MicrosoftZune, requires the use of special management software, such asiTunes or Zune Software, respectively. Over the years, increasingly the players were natively recognised by the operating system throughUniversal Mass Storage (UMS) orMedia Transfer Protocol (MTP).
The music, or other content such as TV episodes or movies, is added to the software to create a "library". The library is then "synced" to the DAP via the software. The software typically provides options for managing situations when the library is too large to fit on the device being synced to. Such options include allowing manual syncing, in that the user can manually "drag-n-drop" the desired tracks to the device, or allow for the creation ofplaylists. In addition to the USB connection, some of the more advanced units are now starting to allow syncing through a wireless connection, such as viaWi-Fi orBluetooth.[20]
Content can also be obtained and placed on some DAPs, such as the iPod Touch or Zune HD by allowing access to a "store" or "marketplace", most notably theiTunes Store orZune Marketplace, from which content, such as music and video, and even games, can be purchased and downloaded directly to the device.
PMPs are capable of playingdigital audio,images, and/orvideo. Usually, a colourliquid crystal display (LCD) ororganic light-emitting diode (OLED) screen is used as a display for PMPs that have a screen. Various players include the ability to record video, usually with the aid of optional accessories or cables, and audio, with a built-inmicrophone or from aline out cable orFM tuner. Some players include readers formemory cards (such asCompactFlash (CF),Secure Digital (SD), andMemory Sticks), which are advertised to equip players with extra storage or transferring media. In some players, features of apersonal organiser are emulated, or support forvideo games, like theiRiver Clix (through compatibility ofAdobe Flash Lite) or thePlayStation Portable, is included. Only mid-range to high-end players support "savestating" for power-off (i.e. leaves off song/video in progress similar to tape-based media).
Nearly all players[21][failed verification] are compatible with the MP3 audio format, and many others supportWindows Media Audio (WMA),Advanced Audio Coding (AAC) andWAV. Some players are compatible with open-source formats likeOgg Vorbis and theFree Lossless Audio Codec (FLAC). Audio files purchased fromonline stores may includedigital rights management (DRM) copy protection, which many modern players support.
TheJPEG format is widely supported by players. Some players, like theiPod series, provide compatibility to display additional file formats likeGIF,PNG, andTIFF, while others are bundled with conversion software.
Most newer players support theMPEG-4 Part 2 video format, and many other players are compatible withWindows Media Video (WMV) andAVI. Software included with the players may be able to convert video files into a compatible format.
Many players have a built-inelectret microphone which allows recording. Usually recording quality is poor, suitable for speech but not music. There are also professional-quality recorders suitable for high-quality music recording with external microphones, at prices starting at a few hundred dollars.
The recording capability means that these players canencode directly to MP3 or other digital audio formats directly from aline-level audio signal.[citation needed]
Some DAPs haveFM radio tuners built in. Many also have an option to change the band from the usual 87.5 – 108.0 MHz to the Japanese band of 76.0 – 90.0 MHz. DAPs typically never have an AM band, or evenHD Radio since such features would be either cost-prohibitive for the application, or because of AM's sensitivity to interference.
Newer portable media players are now coming with Internet access viaWi-Fi. Examples of such devices areAndroid OS devices by various manufacturers, andiOS devices on Apple products like theiPhone,iPod Touch, andiPad. Internet access has even enabled people to use the Internet as an underlying communications layer for their choice of music for automated music randomisation services likePandora, to on-demand video access (which also has music available) such as YouTube. This technology has enabled casual and hobbyist DJs to cue their tracks from a smaller package from an Internet connection, sometimes they will use two identical devices on a crossfade mixer. Many such devices also tend to besmartphones.
Many mobile digital media players havelast position memory, in which when it is powered off, a user does not have to worry about starting at the first track again, or even hearing repeats of others songs when a playlist, album, or whole library is cued forshuffle play, in which shuffle play is a common feature, too. Early playback devices to even remotely have "last position memory" that predated solid-state digital media playback devices were tape-based media, except this kind suffered from having to be "rewound", whereas disc-based media suffered from no native "last position memory", unless disc-players had their own last position memory. However, some models of solid-state flash memory (or hard drive ones with some moving parts) are somewhat the "best of both worlds" in the market.
Media players' firmware may be equipped with a basicfile manager and a text reader.[22] Some portable media players have recently added features such as simple camera, built-in game emulation (playingNintendo Entertainment System or other game formats from ROM images) and simple text readers and editors. Newer PMPs have been able to tell time, and even automatically adjust time according to radio reception, and some devices like the 6th-geniPod Nano even have wristwatch bands available.
Modern MP4 players can playvideo in a multitude ofvideo formats without the need to pre-convert them or downsize them prior to playing them. Some MP4 Players possessUSB ports, to allow users to connect it to apersonal computer tosideload files. Some models also havememory card slots to expand the memory of the player instead of storing files in the built-in memory.
PMPs may come in different form factors such as portrait styled, landscape styled, or keydrive type.Modular MP3keydrive players are composed of twodetachable parts: the head (or reader/writer) and the body (the memory). They can be independently obtained and upgradable (one can change the head or the body; i.e. to add more memory).Display sizes range all the way up to 7 inches (18 cm). Most screens come with a colour depth of 16-bit, but higher quality video-oriented devices may range all the way to 24-bit, otherwise known astrue colour, with the ability to display 16.7 million distinct colours. Screens commonly have a matte finish but may also come in glossy to increase colour intensity and contrast. More and more devices are now also coming with touch screen as a form of primary or alternate input. This can be for convenience and/or aesthetic purposes. Certain devices, on the other hand, have no screen whatsoever, reducing costs at the expense of ease of browsing through the media library.
Today, every smartphone also serves as a portable media player; however, prior to the rise of smartphones in the 2007–2012 time frame, a variety of handheld players were available to store and play music. The immediate predecessor to the portable media player was theportable CD player and prior to that, thepersonal stereo. In particular,Sony'sWalkman andDiscman are the ancestors of digital audio players such as the Apple iPod.[23]
There are several types of MP3 players:
British scientistKane Kramer invented the first digital audio player,[24] which he called theIXI.[25] His 1979 prototypes were capable of up to one hour of audio playback but did not enter commercial production. His UK patent application was not filed until 1981 and was issued in 1985 in the UK and 1987 in the US.[26] However, in 1988 Kramer's failure to raise the £60,000 required to renew the patent meant it entered the public domain.[27]Apple Inc. hired Kramer as a consultant and presented his work as an example ofprior art in the field of digital audio players during their litigation withBurst.com almost two decades later.[28] In 2008, Apple acknowledged Kramer as the inventor of the digital audio player[24][29]
The Listen Up Player was released in 1996 by Audio Highway, an American company led byNathan Schulhof. It could store up to an hour of music, but despite getting an award at CES 1997 only 25 of the devices were made.[30][31] That same yearAT&T developed the FlashPAC digital audio player which initially used AT&T'sPerceptual Audio Coder (PAC)[32] for music compression, but in 1997 switched toAAC.[33] At about the same time AT&T also developed an internal Web-based music streaming service that had the ability to download music to FlashPAC.[34] AAC and such music downloading services later formed the foundation for the Apple iPod and iTunes.[35]
The first production-volume portable digital audio player wasThe Audible Player (also known as MobilePlayer, or Digital Words To Go) fromAudible.com available for sale at the end of 1997, for $199. It only supported playback of digital audio in Audible's proprietary, low-bitrate format which was developed for spoken word recordings. Capacity was limited to 4 MB of internal flash memory, or about 2 hours of play, using a custom rechargeable battery pack. The unit had no display and rudimentary controls.[36][37]
MP3 was introduced as anaudio coding standard in 1992.[38] It was based on severalaudio data compression techniques, including themodified discrete cosine transform (MDCT),FFT andpsychoacoustic methods.[39] MP3 became a popular standard format and as a result most digital audio players after this supported it and hence were often calledMP3 players.
While popularly being called MP3 players at the time, most players could play more than just the MP3 file format. Players also sometimes supportedWindows Media Audio (WMA),Advanced Audio Coding (AAC),Vorbis,FLAC,Speex andOgg.
The first portable MP3 player was launched in 1997 bySaeHan Information Systems,[40] which sold itsMPMan F10 player inSouth Korea in spring 1998.[41][42] In mid-1998, the South Korean company licensed the players for North American distribution to Eiger Labs, which rebranded them as the EigerMan F10 and F20.[43] The flash-based players were available in 32 MB or 64 MB (6 or 12 songs) storage capacity and had a LCD screen to tell the user the song currently playing.
The first car audio hard drive-based MP3 player was also released in 1997 by MP32Go and was called the MP32Go Player. It consisted of a 3 GB IBM 2.5" hard drive that was housed in a trunk-mounted enclosure connected to the car's radio system. It retailed for $599 and was a commercial failure.[44]
TheRio PMP300 fromDiamond Multimedia was introduced in September 1998, a few months after the MPMan, and also featured a 32 MB storage capacity. It was a success during the holiday season, with sales exceeding expectations.[45] Interest and investment in digital music were subsequently spurred from it.[46] TheRIAA soon filed a lawsuit alleging that the device abetted illegal copying of music, but Diamond won a legal victory on the shoulders ofSony Corp. of America v. Universal City Studios, Inc. and MP3 players were ruled legal devices. Because of the player's notoriety as the target of a major lawsuit,[47] the Rio is erroneously assumed to be the first digital audio player.[48]
Eiger Labs and Diamond went on to establish a new segment in the portable audio player market and the following year saw several new manufacturers enter this market. The PMP300 would be the start of theRio line of players. Noticeably, major technology companies did not catch on with the new technology, and instead young startups would come to dominate the early era of MP3 players.
Other early MP3 portables included theCreative Labs Nomad and theRCA Lyra. These portables were small and light, but had only enough memory to hold around 7 to 20 songs at normal 128 kbit/s compression rates. They also used slower parallel port connections to transfer files from PC to player, necessary as most PCs then used theWindows 95 andNT operating systems, which did not have native support forUSB connections.
In 1999 the first hard drive based DAP using a 2.5" laptop drive, thePersonal Jukebox (PJB-100) designed byCompaq and released byHango Electronics Co with 4.8 GB storage, which held about 1,200 songs, and pioneered what would be called the jukebox segment of digital music portables.[49] This segment eventually became the dominant type of digital music player.
Also at the end of 1999 the first in-dash MP3 player appeared. TheEmpeg Car[a] offered players in several capacities ranging from 5 to 28 GB. The unit did not catch on and was discontinued in the fall of 2001.
For the next couple of years, there were offerings fromSouth Korean companies, namely the startupsiRiver (brand of Reigncom),Mpio (brand of DigitalWay) andCowon. At its peak, these Korean makers held as much as 40% world market share in MP3 players.[50] These manufacturers however lost their way after 2004 as they failed to compete with newiPods. By 2006 they were also overtaken by the South Korean giantSamsung Electronics.[51]
Sony entered the digital audio player market in 1999 with theVaio Music Clip andMemory StickWalkman,[52] however they were technically not MP3 players as it did not support the MP3 format but instead Sony's ownATRAC format andWMA. The company's first MP3-supporting Walkman player did not come until 2004.[53] Over the years, various hard-drive-based and flash-based DAPs and PMPs have been released under the Walkman range.
TheSamsung YEPP line was first released in 1999 with the aim of making the smallest music players on the market.[54] In 2000,Creative released the 6 GB hard-drive-basedCreative NOMAD Jukebox. The name borrowed thejukebox metaphor popularised byRemote Solution, also used byArchos. Later players in the Creative NOMAD range usedmicrodrives rather than laptop drives. In October 2000, South Korean software companyCowon Systems released their first MP3 player, the CW100, under the brand nameiAUDIO. In December 2000, some months after the Creative'sNOMAD Jukebox,Archos released itsJukebox 6000 with a 6 GB hard drive.Philips also released a player called the Rush.[55]
On 23 October 2001, Apple unveiled thefirst generation iPod, a 5 GB hard drive based DAP with a 1.8" hard drive and a 2" monochrome display. With the development of a spartanuser interface and a smaller form factor, the iPod was initially popular within theMacintosh community. In July 2002, Apple introduced the second generation update to the iPod, which was compatible withWindows computers throughMusicmatch Jukebox. iPods quickly became the most popular DAP product and led the fast growth of this market during the early and mid 2000s.
In 2002,Archos released the first PMP, theArchos Jukebox Multimedia[56] with a little 1.5" colour screen. The next year, Archos released another multimediajukebox, theAV300, with a 3.8" screen and a 20 GB hard drive. In the same year,Toshiba released the firstGigabeat. In 2003,Dell launched a line of portable digital music players calledDell DJ. They were discontinued by 2006.[57]
The nameMP4 player was a marketing term for inexpensive portable media players, usually from little-known or generic device manufacturers.[58] The name itself is amisnomer, since most MP4 players through 2007 were incompatible with theMPEG-4 Part 14 or the.mp4 container format. Instead, the term refers to their ability to play more file types than just MP3. In this sense, in some markets like Brazil, any new function added to a given media player is followed by an increase in the number, for example an MP5 or MP12 Player,[59] despite there being no such corresponding MPEG standards.
iRiver of South Korea originally made portable CD players and then started making digital audio players and portable media players in 2002. Creative also introduced theZEN line. Both of these attained high popularity in some regions.
In 2004,Microsoft attempted to take advantage of the growing PMP market by launching thePortable Media Center (PMC) platform. It was introduced at the 2004Consumer Electronics Show with the announcement of theZen Portable Media Center,[60] which was co-developed byCreative. The MicrosoftZune series would later be based on theGigabeat S, one of the PMC-implemented players.
In May 2005, flash memory maker SanDisk entered the PMP market with theSansa line of players, starting with the e100 series, and then following up with the m200 series, and c100 series.
Inexpensive generic MP3 players also became popular during the mid 2000s. Many of these were based on theS1 MP3 player and included knock-offs of official brands.
In 2007, Apple introduced theiPod Touch, the first iPod with a multi-touch screen. Some similar products existed before such as theiRiver Clix in 2006. In South Korea, sales of MP3 players peaked in 2006, but started declining afterwards. This was driven partly by the launch of mobile television services (DMB), which along with increased demand of movies on the go led to a transition away from music-only players to PMPs.[61] By 2008, more video-enabled PMPs were sold than audio-only players.[13]
By the mid-2000s and the years after, Apple with its iPod was the best-selling DAP or PMP by a significant margin, with one out of four sold worldwide being an iPod. It was especially dominant in the United States where it had over 70% of sales at different points in time,[12] is nearest competitor in 2006 beingSanDisk.[62] Apple also led in Japan over homegrown makersSony andPanasonic during this time,[62] although the gap between Apple and Sony had closed by about 2010.[63] In South Korea, the market was led by local brands iRiver, Samsung andCowon as of 2005.[64]
European buying patterns differed; while Apple was in a particularly strong position in the United Kingdom, continental Western Europe generally preferred cheaper, often Chinese rebranded players under local brands such asGrundig.[12] Meanwhile, in Eastern Europe including Russia, higher priced players with improved design or functionality were preferred instead. In South Korea makers like iRiver and Samsung were particularly popular, as well as such OEM models under local brands.Creative was the top-selling maker in its home country of Singapore. In China, local brands Newman, DEC and Aigo were noted as the top vendors as of 2006.[62]
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TheSamsung SPH-M2100, the first mobile phone with built-in MP3 player was produced inSouth Korea in August 1999.[65][66] TheSamsung SPH-M100 (UpRoar) launched in 2000 was the first mobile phone to have MP3 music capabilities[67] in the US market. The innovation spread rapidly and by 2005, more than half of all music sold in South Korea was sold directly to mobile phones and all major handset makers in the world had released MP3 playing phones. By 2006, more MP3-playing mobile phones were sold than all stand-alone MP3 players. Apple cited the rapid rise of the media player in phones as a primary reason for developing theiPhone.[citation needed] In 2007, the number of phones that could play media was over 1 billion.[citation needed] Some companies created music-centric sub-brands for mobile phones, for example the formerSony Ericsson'sWalkman range orNokia'sXpressMusic range, which have extra emphasis on music playback and typically have features such as dedicated music buttons.[68]
Mobile phones with PMP functionalities such as video playback also started appearing in the 2000s. Other non-phone products such as thePlayStation Portable andPlayStation Vita have also been considered to be PMPs.
PMPs have declined in popularity after the late 2000s due to increasing worldwide adoption ofsmartphones that include PMP functionalities. Sales peaked in 2007 and market revenue peaked in 2008 atUS$21.6 billion. Mobile phones that could play music outsold DAPs by almost three to one in 2007.[12]
In theEU, demand for MP3 players peaked in 2007 with 43.5 million devices sold, totalling€3.8 billion. Both sales and revenue experienced a double-digit shrinkage for the first time in 2010.[69] In India, sales of PMPs decreased for the first time in 2012, a few years after the decline in developed economies.[70]
Meanwhile, sales of Apple's best-selling PMP product, the iPod, were eclipsed by theiPhone in 2011.[71]
DAPs continue to be made in lower volumes by manufacturers such as SanDisk, Sony, iRiver, Philips, Cowon, and a range of Chinese manufacturers namely Aigo, Newsmy, PYLE and ONDA.[72] They often have specific selling points in the smartphone era, such as portability or for high quality sound suited foraudiophiles.
There are three categories of audio formats:
There are also royalty-free lossy formats likeVorbis for general music andSpeex andOpus used for voice recordings. When "ripping" music from CDs, many people recommend the use oflossless audio formats to preserve the CD quality in audio files on a desktop, and to transcode the music tolossy compression formats when they are copied to a portable player.[74] The formats supported by a particular audio player depends upon itsfirmware; sometimes a firmware update adds more formats. MP3 andAAC are dominant formats,[74] and are almost universally supported.[75]
Chipsets and file formats that are particular to some PMPs:
The image compression algorithm of this format[78] is inefficient by modern standards (about 4 pixels per byte, compared with over 10 pixels per byte forMPEG-2). There are a fixed range of resolutions (96 × 96 to 208 × 176 pixels) and framerates (12 or 16frames) available. However it can be used with limited hardware requirements. A 30-minute video would have a filesize of approximately 100 MB at a 160 × 120 resolution.[79]
The MTV video format (no relation to thecable network) consists of a 512-byte file header that operates by displaying a series of raw image frames duringMP3 playback.[79] During this process, audio frames are passed to the chipset's decoder, while the memory pointer of the display's hardware is adjusted to the next image within the video stream. This method does not require additional hardware for decoding, though it will lead to a higher amount of memory consumption. For that reason, the storage capacity of an MP4 player that uses MTV files is effectively less than that of a player that decompresses files on the fly.
A growing number of portable media players are including audio processing chips that allow digital effects like3D audio effects,dynamic range compression andequalisation of thefrequency response.[80][81][82][83] Some devices adjust loudness based onFletcher–Munson curves. Some media players are used withNoise-cancelling headphones that useActive noise reduction to remove background noise.
De-noise mode is an alternative toActive noise reduction. It provides for relatively noise-free listening to audio in a noisy environment. In this mode, audio intelligibility is improved due to selective gain reduction of the ambient noise. This method splits external signals into frequency components by "filterbank" (according to the peculiarities of human perception of specific frequencies) and processing them using adaptiveaudio compressors. Operation thresholds in adaptive audio compressors (in contrast to "ordinary" compressors) are regulated depending onambient noise levels for each specific bandwidth. Reshaping of the processed signal from adaptive compressor outputs is realised in a synthesis filterbank. This method improves the intelligibility of speech signals and music. The best effect is obtained while listening to audio in the environment with constant noise (in trains, automobiles, planes), or in environments with fluctuating noise level (e.g. in a metro). Improvement of signal intelligibility in condition of ambient noise allows users to hear audio well and preserve hearing ability, in contrast to regular volume amplification.
Natural mode is characterised by subjective effect of balance of different frequency sounds, regardless of level of distortion, appearing in the reproduction device. It is also regardless of personal user's ability to perceive specific sound frequencies (excluding obvious hearing loss). The natural effect is obtained due to special sound processing algorithm (i.e. "formula of subjective equalisation of frequency-response function"). Its principle is to assessfrequency response function (FRF) of mediaplayer or any other sound reproduction device, in accordance with audibility threshold in silence (subjective for each person),[84] and to apply gain modifying factor. The factor is determined with the help of integrated function to test audibility threshold: the program generates tone signals (with divergent oscillations – from minimum volume 30–45 Hz to maximum volume appr. 16 kHz),[85] and user assess their subjective audibility. The principle is similar toin situ audiometry, used in medicine to prescribe a hearing aid. However, the results of test may be used to a limited extent as far as FRF of sound devices depends on reproduction volume. It means correction coefficient should be determined several times – for various signal strengths, which is not a particular problem from a practical standpoint.
Sound around mode allows for real time overlapping of music and the sounds surrounding the listener in their environment, which are captured by a microphone and mixed into the audio signal. As a result, the user may hear playing music and external sounds of the environment at the same time. This can increase user safety (especially in big cities and busy streets), as a user can hear amugger following them or hear an oncoming car.
Although these issues are not usually controversial within digital audio players, they are matters of continuing controversy and litigation, including but not limited to content distribution and protection, anddigital rights management (DRM).
TheRecording Industry Association of America (RIAA) filed a lawsuit in late 1998 againstDiamond Multimedia for itsRio players,[47][86] alleging that the device encouraged copying music illegally. But Diamond won a legal victory on the shoulders of theSony Corp. v. Universal City Studios case and DAPs were legally ruled as electronic devices.[87]
According to theScientific Committee on Emerging and Newly Identified Health Risks, the risk ofhearing damage from digital audio players depends on both sound level and listening time. The listening habits of most users are unlikely to cause hearing loss, but some people are putting their hearing at risk, because they set the volume control very high or listen to music at high levels for many hours per day. Such listening habits may result in temporary or permanent hearing loss,tinnitus, and difficulties understanding speech in noisy environments.TheWorld Health Organization warns that increasing use of headphones and earphones puts 1.1 billion teenagers and young adults at risk of hearing loss due to unsafe use of personal audio devices.[88] Manysmartphones and personal media players are sold with earphones that do a poor job of blocking ambient noise, leading some users to turn up the volume to the maximum level to drown out street noise.[89] People listening to their media players on crowded commutes sometimes play music at high volumes feel a sense of separation, freedom and escape from their surroundings.[90][91]
The World Health Organization recommends that "the highest permissible level of noise exposure in the workplace is 85 dB up to a maximum of eight hours per day" and time in "nightclubs, bars and sporting events" should be limited because they can expose patrons to noise levels of 100 dB. The report states
Teenagers and young people can better protect their hearing by keeping the volume down on personal audio devices, wearing earplugs when visiting noisy venues, and using carefully fitted, and, if possible,noise-cancelling earphones/headphones. They can also limit the time spent engaged in noisy activities by taking short listening breaks and restricting the daily use of personal audio devices to less than one hour. With the help of smartphone apps, they can monitor safe listening levels.
The report also recommends that governments raise awareness of hearing loss, and to recommend people visit a hearing specialist if they experience symptoms of hearing loss, which include pain, ringing or buzzing in the ears.[92]
A study by theNational Institute for Occupational Safety & Health found that employees at bars, nightclubs or other music venues were exposed to noise levels above the internationally recommended limits of 82–85 dBA per eight hours. This growing phenomena has led to the coining of the term music-induced hearing loss, which includes hearing loss as a result of overexposure to music on personal media players.[93]
In 2009 the European Union drafted a law to force manufacturers to cap the maximum volume output on players to 80 dB.[94]
Some MP3 players have electromagnet transmitters, as well as receivers. Many MP3 players have built-in FM radios, butpersonal FM transmitters are not usually built-in due to liability of transmitterfeedback from simultaneous transmission and reception of FM. Also, certain features like Wi-Fi and Bluetooth can interfere with professional-grade communications systems such as aircraft at airports.[95]
Most support the patented MP3 codec, but not all. To call such players 'MP3 players' is not only confusing,... We suggest the terms 'digital audio player,' or simply 'audio player' if context permits.
{{cite magazine}}:Missing or empty|title= (help)Virtual Stereo Surround – Multiband Compressor – Tone Control – Bass Manager – Bass Enhancer – Dynamic Volume Leveler – Multichannel Surround – Crossbar Mixer – Speaker Protection – Dolby Digital Post-processing Support
bass management, 3D virtual surround, Lucasfilm THX5.1, soundfield processing, and advanced equalization
{{cite web}}: CS1 maint: archived copy as title (link)
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