iPod.

The iPod is a line of portable media players and multi-purpose pocket computers designed and marketed by Apple Inc. The first line was released on October 23, 2001, about 8½ months after iTunes (Macintosh version) was released. The most recent iPod redesigns were announced on July 15, 2015. There are three current versions of the iPod: the ultra-compact iPod Shuffle, the compact iPod Nano and the touchscreen iPod Touch.

Like other digital music players, iPods can serve as external data storage devices. Storage capacity varies by model, ranging from 2 GB for the iPod Shuffle to 128 GB for the iPod Touch (previously 160 GB for the iPod Classic, which is now discontinued).

Apple's iTunes software (and other alternative software) can be used to transfer music, photos, videos, games, contact information, e-mail settings, Web bookmarks, and calendars, to the devices supporting these features from computers using certain versions of Apple Macintosh and Microsoft Windows operating systems.

Before the release of iOS 5, the iPod branding was used for the media player included with the iPhone and iPad, a combination of the Music and Videos apps on the iPod Touch. As of iOS 5, separate apps named "Music" and "Videos" are standardized across all iOS-powered products. While the iPhone and iPad have essentially the same media player capabilities as the iPod line, they are generally treated as separate products. During the middle of 2010, iPhone sales overtook those of the iPod.

In mid-2015, a new model of the iPod Touch was announced by Apple, and was officially released on the Apple store on July 15, 2015. The sixth generation iPod Touch includes a wide variety of spec improvements such as the upgraded A8 processor and higher-quality screen. The core is over 5 times faster than previous models and is built to be roughly on par with the iPhone 5S. It is available in 5 different colors: Space grey, pink, gold, silver and Product (red).

Hardware

Chipsets and Electronics
Chipset or Electronic	Product(s)	Component(s)
Microcontroller	iPod Classic 1st to 3rd generations	Two ARM 7TDMI-derived CPUs running at 90 MHz
	iPod Classic 4th and 5th generations, iPod Mini, iPod Nano 1st generation	Variable-speed ARM 7TDMI CPUs, running at a peak of 80 MHz to save battery life
	iPod Classic 6th generation, iPod Nano 2nd generation onwards, iPod Shuffle 2nd generation onwards	Samsung System-on-a-chip, based around an ARM processor.
	iPod Shuffle 1st generation	SigmaTel D-Major STMP3550 chip running at 75 MHz that handles both the music decoding and the audio circuitry.
	iPod Touch 1st and 2nd generation	ARM 1176JZ(F)-S at 412 MHz for 1st gen, 533 MHz for 2nd gen.
	iPod Touch 3rd and 4th generation	ARM Cortex A8 at 600 MHz for 3rd gen, 800 MHz for 4th gen.
	iPod Touch 5th generation	ARM Cortex A9 at 800 MHz
	iPod Touch 6th generation	Apple ARMv8-A "Typhoon" at 1.1 GHz
Audio Chip	iPod Classic 1st to 5th generation, iPod Touch 1st generation, iPod Nano 1st to 3rd generation, iPod Mini	Audio Codecs developed by Wolfson Microelectronics
	iPod Classic 6th generation, iPod Touch 2nd generation onwards, iPod Shuffle, iPod Nano 4th generation onwards	Cirrus Logic Audio Codec Chip
Storage Medium	iPod Classic	45.7 mm (1.8 in) hard drives (ATA-6, 4200 rpm with proprietary connectors) made by Toshiba
	iPod Mini	25.4 mm (1 in) Microdrive by Hitachi and Seagate
	iPod Nano	Flash Memory from Samsung, Toshiba, and others
	iPod Shuffle and Touch	Flash Memory
Batteries	iPod Classic 1st and 2nd generation	Internal Lithium Polymer Batteries
	iPod Classic 3rd generation onwards, iPod Mini, iPod Nano, iPod Touch, iPod Shuffle	Internal Lithium-Ion Batteries
Display	iPod Nano 7th generation	2.5-inch (diagonal) Multi-Touch, 432-by-240 resolution at 202 pixels per inch
	iPod Classic 5th and 6th generation	2.5-inch (diagonal) color LCD with LED backlight, 320-by-240 resolution at 163pixels per inch
	iPod Touch 5th and 6th generation	4-inch (diagonal) widescreen Multi-Touch, 1136-by-640 resolution at 326 pixels per inch

 

Audio

 

The third-generation iPod had a weak bass response, as shown in audio tests. The combination of the undersized DC-blocking capacitors and the typical low-impedance of most consumer headphones form a high-pass filter, which attenuates the low-frequency bass output. Similar capacitors were used in the fourth-generation iPods. The problem is reduced when using high-impedance headphones and is completely masked when driving high-impedance (line level) loads, such as an external headphone amplifier. The first-generation iPod Shuffle uses a dual-transistor output stage, rather than a single capacitor-coupled output, and does not exhibit reduced bass response for any load.

For all iPods released in 2006 and earlier, some equalizer (EQ) sound settings would distort the bass sound far too easily, even on undemanding songs. This would happen for EQ settings like R&B, Rock, Acoustic, and Bass Booster, because the equalizer amplified the digital audio level beyond the software's limit, causing distortion (clipping) on bass instruments.

From the fifth-generation iPod on, Apple introduced a user-configurable volume limit in response to concerns about hearing loss. Users report that in the sixth-generation iPod, the maximum volume output level is limited to 100 dB in EU markets. Apple previously had to remove iPods from shelves in France for exceeding this legal limit. However, users that have bought a new sixth-generation iPod in late 2013 have reported a new option that allowed them to disable the EU volume limit. It has been said that these new iPods came with an updated software that allowed this change. Older sixth-generation iPods, however, are unable to update to this software version.

 

Connectivity

 

Four iPod wall chargers for North America, all made by Apple. These have FireWire (left) and USB (right three) connectors, which allow iPods to charge without a computer. The units have been miniaturized over time.

Originally, a FireWire connection to the host computer was used to update songs or recharge the battery. The battery could also be charged with a power adapter that was included with the first four generations.

The third generation began including a 30-pin dock connector, allowing for FireWire or USB connectivity. This provided better compatibility with non-Apple machines, as most of them did not have FireWire ports at the time. Eventually Apple began shipping iPods with USB cables instead of FireWire, although the latter was available separately. As of the first-generation iPod Nano and the fifth-generation iPod Classic, Apple discontinued using FireWire for data transfer (while still allowing for use of FireWire to charge the device) in an attempt to reduce cost and form factor. As of the second-generation iPod Touch and the fourth-generation iPod Nano, FireWire charging ability has been removed. The second-, third-, and fourth-generation iPod Shuffle uses a single 3.5 mm minijack phone connector which acts as both a headphone jack and a data port for the dock.

The dock connector also allowed the iPod to connect to accessories, which often supplement the iPod's music, video, and photo playback. Apple sells a few accessories, such as the now-discontinued iPod Hi-Fi, but most are manufactured by third parties such as Belkin and Griffin. Some peripherals use their own interface, while others use the iPod's own screen. Because the dock connector is a proprietary interface, the implementation of the interface requires paying royalties to Apple.

Apple introduced a new 8-pin dock connector, named Lightning, on September 12, 2012 with their announcement of the iPhone 5, the fifth generation iPod Touch, and the seventh generation iPod Nano, which all feature it. The new connector replaces the older 30-pin dock connector used by older iPods, iPhones, and iPads. Apple Lightning cables have pins on both sides of the plug so it can be inserted with either side facing up.

Software

The iPod line can play several audio file formats including MP3, AAC/M4A, Protected AAC, AIFF, WAV, Audible audiobook, and Apple Lossless. The iPod photo introduced the ability to display JPEG, BMP, GIF, TIFF, and PNG image file formats. Fifth and sixth generation iPod Classics, as well as third generation iPod Nanos, can additionally play MPEG-4 (H.264/MPEG-4 AVC) and QuickTime video formats, with restrictions on video dimensions, encoding techniques and data-rates. Originally, iPod software only worked with Mac OS; iPod software for Microsoft Windows was launched with the second generation model. Unlike most other media players, Apple does not support Microsoft's WMA audio format—but a converter for WMA files without Digital Rights Management (DRM) is provided with the Windows version of iTunes. MIDI files also cannot be played, but can be converted to audio files using the "Advanced" menu in iTunes. Alternative open-source audio formats, such as Ogg Vorbis and FLAC, are not supported without installing custom firmware onto an iPod (e.g., Rockbox).

During installation, an iPod is associated with one host computer. Each time an iPod connects to its host computer, iTunes can synchronize entire music libraries or music playlists either automatically or manually. Song ratings can be set on an iPod and synchronized later to the iTunes library, and vice versa. A user can access, play, and add music on a second computer if an iPod is set to manual and not automatic sync, but anything added or edited will be reversed upon connecting and syncing with the main computer and its library. If a user wishes to automatically sync music with another computer, an iPod's library will be entirely wiped and replaced with the other computer's library.

 

Interface

 

The signature iPod click wheel.

iPods with color displays use anti-aliased graphics and text, with sliding animations. All iPods (except the 3rd-generation iPod Shuffle, the 6th & 7th generation iPod Nano, and iPod Touch) have five buttons and the later generations have the buttons integrated into the click wheel – an innovation that gives an uncluttered, minimalist interface. The buttons perform basic functions such as menu, play, pause, next track, and previous track. Other operations, such as scrolling through menu items and controlling the volume, are performed by using the click wheel in a rotational manner. The 3rd-generation iPod Shuffle does not have any controls on the actual player; instead it has a small control on the earphone cable, with volume-up and -down buttons and a single button for play and pause, next track, etc. The iPod Touch has no click-wheel; instead it uses a 3.5" touch screen along with a home button, sleep/wake button and (on the second and third generations of the iPod Touch) volume-up and -down buttons. The user interface for the iPod Touch is identical to that of the iPhone. Differences include a lack of a phone application. Both devices use iOS.

iTunes Store

The iTunes Store (introduced April 29, 2003) is an online media store run by Apple and accessed through iTunes. The store became the market leader soon after its launch and Apple announced the sale of videos through the store on October 12, 2005. Full-length movies became available on September 12, 2006.

At the time the store was introduced, purchased audio files used the AAC format with added encryption, based on the FairPlay DRM system. Up to five authorized computers and an unlimited number of iPods could play the files. Burning the files with iTunes as an audio CD, then re-importing would create music files without the DRM. The DRM could also be removed using third-party software. However, in a deal with Apple, EMI began selling DRM-free, higher-quality songs on the iTunes Stores, in a category called "iTunes Plus." While individual songs were made available at a cost of US$1.29, 30¢ more than the cost of a regular DRM song, entire albums were available for the same price, US$9.99, as DRM encoded albums. On October 17, 2007, Apple lowered the cost of individual iTunes Plus songs to US$0.99 per song, the same as DRM encoded tracks. On January 6, 2009, Apple announced that DRM has been removed from 80% of the music catalog, and that it would be removed from all music by April 2009.

iPods cannot play music files from competing music stores that use rival-DRM technologies like Microsoft's protected WMA or RealNetworks' Helix DRM. Example stores includeNapster and MSN Music. RealNetworks claims that Apple is creating problems for itself by using FairPlay to lock users into using the iTunes Store. Steve Jobs stated that Apple makes little profit from song sales, although Apple uses the store to promote iPod sales. However, iPods can also play music files from online stores that do not use DRM, such as eMusic or Amie Street.

Universal Music Group decided not to renew their contract with the iTunes Store on July 3, 2007. Universal will now supply iTunes in an 'at will' capacity.

Apple debuted the iTunes Wi-Fi Music Store on September 5, 2007, in its Media Event entitled "The Beat Goes On...". This service allows users to access the Music Store from either an iPhone or an iPod Touch and download songs directly to the device that can be synced to the user's iTunes Library over a Wifi connection, or, in the case of an iPhone, the telephone network.

Timeline of iPod models and related products

Source: https://en.wikipedia.org/wiki/IPod