About Digital Music Technology


"But wait," you might be saying. "I thought compact discs were all about digital audio, which is what made them better than cassette tapes 20 years ago. How is that different from what is considered digital music in the iTunes' world?" And that's a fair question. In fact, it's got a good illustration built right into it. Think of digital music in the iTunes' age as being to CDs what CDs were to tapes. CDs are a digital medium, which means that the player can access any given song on the disc on command; with a CD, you can do such things as program the tracks to play in a certain order, randomly select songs from various discs in a changer, and so on. These features just weren't possible on an analog medium like the cassette tape, where the audio content consists of nothing more than a long, unbroken stream of magnetic material that is interpreted during playback as louder or softer sounds. The same huge leap in flexibility that we enjoyed in moving from tapes or vinyl records to CDs is now present as we move from CDs to pure digital music on our computers: Instead of the music data being stored on a physical disc that has to be moved around and manually loaded into a player, it's stored in the form of easily portable data files that can be played back in any order, modified, or copied from device to device by simply giving a command in software.

To accomplish this quantum leap in portability and control, a certain breakthrough or two was necessary. In the mid-1990s, these breakthroughs occurred. First, a compression algorithm was developed that shrunk the digital audio data from the uncompressed format in which it's stored on CDs (about 10MB per minute, far too large to be practical) to one in which large music collections could be conveniently stored on typical computer hard drives or transferred easily over the Internet. Additionally, processor speeds rose to the point where desktop computers could quickly and easily convert CD music data to the compressed format.

The MP3 Revolution

Developed in the early 1990s, MPEG-1 level 3 (MP3) became the first widely accepted encoding format that enabled the meteoric rise of digital music, even though it was underground and largely illicit at first. College students and young computer geeks with fast Internet connections used free or inexpensive encoding software (licensed from bodies such as the Fraunhofer Institute that holds the rights to the MP3 encoding algorithm) to convert its purchased CDs into MP3 format. After they were converted to the compressed digital form, these files immediately took on a life of their own, taking advantage of the files' relatively small size (usually 3 to 5 megabytes per song) and the explosive growth of the Internet to leap from computer to computer by way of the new breed of "peer-to-peer" software (such as Napster) that allowed MP3 collectors to seek out music on others' computers and quickly download it. Artists and record labels initially dismissed the threat that MP3 file sharing presented to their business model. However, soon it became apparent that the problem was not going to go away on its ownCD sales were slipping noticeably, and it would only get worse with time. A few high-profile lawsuits against MP3 collectors and broadcasters, and the legal shutdown of the Napster service, officially placed free music file sharing into the public eyeto some, an honorable form of rebellion against corporate tyranny ; to others, the very act of killing the goose that lays the golden eggs.

KEY TERM

MPEG-1 level 3 (MP3) The most widely used format for digital music, MP3 files sound pretty good but have no copy protection built in.


There was no denying the benefit of digital music, after all. It's always been perfectly legal to copy a CD to MP3 format for your own use; it's just the unrestricted transmission of these unprotected music files to other, unrelated computer users that's illegal and a violation of copyright law. As long as you're using MP3s responsibly, if you've used them once, it's hard to go back. The convenience of playing a favorite song with a simple double-clickinstead of digging out a CD and skipping to the appropriate numbered track as directed by the liner notesis a difference of night and day. Similarly, CDs simply cannot compare to the organizational benefits of setting the info tags (or ID3 tags ) on files so that you can immediately navigate to them by publication year, genre , track number, beats per minute, or even embedded album art images. Creating a mix CD from MP3 files is a giant leap above manually dubbing songs to a mix cassette tape as in the old daysthen a laborious, hours-long process. Today, it involves little more than arranging the appropriate files in the right order, inserting a writable CD, and clicking a "burn" button.

KEY TERM

Info tags Data fields built into a digital audio file that contain the song's title, artist, album, track number, album art, and other information. Often called ID3 tags in MP3 files; also referred to generically as metadata .


The small size and platform-independence of MP3 files led to the inevitable creation of portable music players such as the iPod. Because MP3 files didn't actually take up any physical space to speak of (unlike music on CDs), the only limitation on how small a portable device could be made was in how large the screen and controls had to be to allow for easy navigation of your music. As an illustration, the iPod can't be made much smaller than the iPod mini varietyeven if hard drive technology allowed the same storage capacity in a smaller packagebecause the user still has to work the wheel and buttons with her thumb, and the screen must be large enough to be readable while still retaining the six or seven lines of textual information that make the iPod's scrolling navigation so usable. These limitations are a far cry from the ones that dictate the shape of a portable CD player: no matter how small the technology of such a device gets, the overall unit can never get smaller than the five-inch bulk of a CD. (Also the user has to hold it horizontally and keep it from being jolted, which is all but an irrelevancy to digital music playersespecially solid-state ones like the iPod shuffle.)

Going Legit

MP3 had its day in the sun, symbolizing the freedom of digital music as well as the irresponsibility that inevitably comes with such freedom. However, it was not to last. If digital music were to become a mainstream medium to rival or even replace CDs, it could not be on the MP3 formatbecause as soon as a record label sold an MP3, the purchaser could immediately turn around and broadcast it onto the peer-to-peer file-sharing networks (which have never gone awayrather, they've merely become more and more sneaky and undetectable by the authorities). Some online digital music stores, such as MP3.com and eMusic.com, have attempted to make a business case on selling MP3s created by artists who don't care about piracy and are only interested in exposure to their fansbut those artists are relatively few and don't include any of the big- name stars whose music most listeners want to buy.

The answer finally came when Apple introduced Advanced Audio Coding ( AAC ) , a digital music format similar to MP3 but protected with digital signatures that ensure that only a limited number of "authorized" computers can open or play a given file. This format was introduced at the same time as the iTunes Music Store, which opened the doors of legal music downloads for both Mac and Windows users. AAC files' Digital Rights Management ( DRM ) technology gave the record industry the assurance it needed that the products it sold would not be devalued through immediate and uncontrollable duplication.

KEY TERM

Digital Rights Management (DRM) Software algorithms that provide "copy protection" for digital music, usually enforced with digital "keys."


Because of the DRM-protected flavor of the AAC format, record labels at last gave the nod to Apple, and it's because of the selection of popular music made available by that deal that the iTunes Music Store has become so popular where other similar ventures without industry-placating safeguards have failed. Built directly into iTunes, the Music Store is an online library of over a million downloadable tracks in thousands of albums by the most popular commercial artists and obscure cult idols alike. Leading the market by a wide margin, the iTunes Music Store lets you buy music through an online account and download it directly into your iTunes Music Library . A single customer's purchased music, in AAC format, can be copied and played back on as many as five different computers, whether Windows PCs or Macs. This requires an Internet-based authorization process for each computer, however, and without that authorization the files cannot be opened. To read more about the details of the DRM technology used in iTunes and the AAC format, turn to 17 About Digital Rights Management Technology .

Fortunately, AAC files bring more to the table than just DRM restrictions; they also boast better audio quality and compression efficiency than MP3 files, making them smaller and clearer than MP3 files under most circumstances, with true separate stereo tracks and a more efficient codec (encoding and decoding) algorithm. This gives users their own good reasons to opt for AAC (which can be optionally encoded without any DRM restrictions, for example if you're importing your own CDs) instead of MP3.

NOTE

Windows Media Audio (WMA) provides similar features and benefits over MP3, although the DRM infrastructure used in WMA files (depending on the specific implementation used by a retailer) can be more restrictive than what is found in AAC.


The downside of AAC files is that they're not as widely used as MP3 or even WMA files. Nearly all digital audio players can play MP3 files, and many can now handle WMA files as well. However, only the iPod can play AAC files. Considering that the iPod is the world's most popular portable digital music player by a huge margin, though, perhaps that is no drawback.

NOTE

iTunes supports several digital music formats other than MP3 and AAC, as described in fuller detail in 8 About Music Formats. AIFF and WAV , both uncompressed formats, preserve flawless CD-quality audio at the expense of disk space. Apple Lossless is a format that halves the size of uncompressed CD audio with no loss of quality. iTunes for Windows can even import unprotected WMA files by converting them to AAC format; see 2 Run iTunes for the First Time and 11 Add a Music File to Your iTunes Library for more information.


With today's computer-component technology, a desktop PC or Mac can encode a full-length CD to MP3 or AAC format in as little as 1/20th the time it takes to play it all the way through at normal speed. The resulting files usually take up between 30 and 70 megabytes of space on your disk; this means that on a 120GB hard disk (a typical mid-range size for a desktop computer in 2005), you can potentially store about 2,500 CDs' worth of music, or 30,000 individual songs.

Besides which, with iTunes and the iPod, you can immediately dial up exactly the song, artist, or album you want to hear, without having to get up from your seat. That's a lot better than keeping your music discs in a disorganized, overflowing rack against your wall, isn't it?



iPod + iTunes for Windows and Mac in a Snap
iPod + iTunes for Windows and Mac in a Snap (2nd Edition)
ISBN: 0672328992
EAN: 2147483647
Year: 2005
Pages: 152
Authors: Brian Tiemann

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