Editing Portable media player (section)

==Operation==
[[File:Sansa Clip (Clip).JPG|thumb|A [[SanDisk Sansa|Sansa Clip]] player with a clip to attach on a person's clothing]]
[[Sampling (signal processing)|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, an [[embedded processor]], and an audio [[codec]] microchip to convert the compressed file into an analogue sound signal. During playback, audio files are read from storage into a [[RAM]] based memory buffer, and then streamed through an audio codec to produce decoded [[PCM]] audio. Typically audio formats decode at double to more than 20 times real speed on portable electronic [[Central processing unit|processors]],<ref>{{cite web |title=Codec Performance Comparison |url=http://www.rockbox.org/wiki/CodecPerformanceComparison |url-status=live |archive-url=https://web.archive.org/web/20120528090734/http://www.rockbox.org/wiki/CodecPerformanceComparison |archive-date=28 May 2012 |access-date=10 November 2012 |publisher=rockbox.org |df=dmy-all}}</ref> requiring that the codec output be stored for a time until the [[Digital-to-analog converter|DAC]] 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 by [[rechargeable batteries]], some of which are not user-replaceable. They have a 3.5&nbsp;mm stereo jack; music can be listened to with [[Headphones|earbuds]] or [[headphones]], or played via an external amplifier and [[loudspeaker|speakers]]. Some devices also contain internal speakers, through which music can be listened to, although these built-in speakers are typically of very low quality.

=== Display and interface ===
[[File:IPodShuffle.jpg|thumb|left|An [[iPod Shuffle]] DAP, featuring no display screen]]
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. The display, if the unit even has one, can be anything from a simple one or two line monochrome [[LCD]] display, similar to what are found on typical [[pocket calculator]]s, 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 typical [[CD player]]s, such as for skipping through tracks or stopping/starting playback to full touch-screen controls, such as that found on the [[iPod Touch]] or the [[Zune HD]]. One of the more common methods of control is some type of the [[scroll 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-way [[D-pad]] to navigate. Many alternatives have been used, most notably the wheel and touch mechanisms seen on players from the [[iPod]] and [[SanDisk Sansa|Sansa series]]. Another popular mechanism is the swipe-pad, or 'squircle', first seen on the [[Zune]]. Additional buttons are commonly seen for features such as volume control.

=== Syncing and software ===
[[File:Sandisk Sansa Clip.JPG|thumb|right|200px|Connecting a computer to a [[SanDisk Sansa|Sansa Clip]] DAP to transfer content by "syncing"]]
[[File:NETrax mp3 player with docking station.png|thumb|An early DAP (NETrax, from 1999) in its dedicated [[docking station]] for charging and connecting to a PC]]
Content is placed on DAPs typically through a process called "syncing", by connecting the device to a personal computer, typically via [[USB]], and running any special software that is often provided with the DAP on a [[CD-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 Microsoft [[Zune]], requires the use of special management software, such as [[iTunes]] or Zune Software, respectively. Over the years, increasingly the players were natively recognised by the operating system through [[USB mass storage device class|Universal Mass Storage]] (UMS) or [[Media 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 of [[playlist]]s. In addition to the USB connection, some of the more advanced units are now starting to allow syncing through a wireless connection, such as via [[Wi-Fi]] or [[Bluetooth]].<ref>{{cite web |title=MP3 streaming over Bluetooth |url=http://www.clarinox.com/docs/whitepapers/Whitepaper_05_MP3.pdf |url-status=live |archive-url=https://web.archive.org/web/20110219200056/http://www.clarinox.com/docs/whitepapers/Whitepaper_05_MP3.pdf |archive-date=19 February 2011 |access-date=4 August 2010 |publisher=clarinox |df=dmy-all}}</ref>

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 the [[iTunes Store]] or [[Zune Marketplace]], from which content, such as music and video, and even games, can be purchased and downloaded directly to the device.