Portable media player
[19] Apple Inc. hired Kramer as a consultant and presented his work as an example of prior art in the field of digital audio players during their litigation with Burst.com almost two decades later.
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.
[30] It was based on several audio data compression techniques, including the modified discrete cosine transform (MDCT), FFT and psychoacoustic methods.
[33][34] 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.
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.
With the development of a spartan user interface and a smaller form factor, the iPod was initially popular within the Macintosh community.
In 2004, Microsoft attempted to take advantage of the growing PMP market by launching the Portable Media Center (PMC) platform.
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.
[56] 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 as Grundig.
DAPs and PMPs have declined in popularity after the late 2000s due to increasing worldwide adoption of smartphones that already come with PMP functionalities.
[64] They often have specific selling points in the smartphone era, such as portability (for small sized players) or for high quality sound suited for audiophiles.
In some players, features of a personal organiser are emulated, or support for video games, like the iRiver Clix (through compatibility of Adobe Flash Lite) or the PlayStation Portable, is included.
Audio files purchased from online stores may include digital rights management (DRM) copy protection, which many modern players support.
Some players, like the iPod series, provide compatibility to display additional file formats like GIF, PNG, and TIFF, while others are bundled with conversion software.
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.
For later players, however, these are usually available online via the manufacturers' websites, or increasingly natively recognised by the operating system through Universal Mass Storage (UMS) or Media Transfer Protocol (MTP).
[73] The MTV video format (no relation to the cable network) consists of a 512-byte file header that operates by displaying a series of raw image frames during MP3 playback.
[73] 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.
Nearly all DAPs consists of some kind of display screen, although there are exceptions, such as the iPod 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.
Natural mode is characterised by subjective effect of balance of different frequency sounds, regardless of level of distortion, appearing in the reproduction device.
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 assess frequency response function (FRF) of mediaplayer or any other sound reproduction device, in accordance with audibility threshold in silence (subjective for each person),[80] and to apply gain modifying factor.
The Recording Industry Association of America (RIAA) filed a lawsuit in late 1998 against Diamond Multimedia for its Rio players,[39][82] alleging that the device encouraged copying music illegally.
Such listening habits may result in temporary or permanent hearing loss, tinnitus, and difficulties understanding speech in noisy environments.
The World 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.
[85] 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.
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.
[88] A study by the National 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.
