`
`MP3: The Definitive Guide
`
`Scot Hacker
`
`Publisher: O'Reilly
`
`First Edition March 2000
`ISBN: 1-56592-661-7, 400 pages
`
`
`
`
`MP3: The Definitive Guide introduces the power-user to just
`about all aspects of MP3 technology. It delves into detail on
`obtaining, recording, and optimizing MP3 files using both
`commercial and Open Source methods. Coverage is complete
`for four platforms: Windows, Macintosh, Linux, and BeOS. In-
`depth chapters describe all aspects of the MP3 experience from
`distributing, streaming, broadcasting, converting, and playing
`to archiving your collection. Readers will learn how to test
`their equipment, optimize their encoding times, evaluate their
`playback options, control and organize a collection, and even
`burn their own CD's or distribute their own music to a massive
`worldwide audience over the Internet. In addition, the author
`fills readers in on the complex legal issues surrounding MP3
`files. Everything you need to know to enjoy MP3 today and
`tomorrow is contained in this single volume.
`
`web
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`Distribution
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`$
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`$
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`buy
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`Yes
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`Downloading
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`Reading
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`No
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`Yes
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`Fast
`Network?
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`Copyright © 2000 O'Reilly & Associates, Inc. All rights reserved.
`
`Printed in the United States of America.
`
`Published by O'Reilly & Associates, Inc., 101 Morris Street, Sebastopol, CA 95472.
`
`The O'Reilly logo is a registered trademark of O'Reilly & Associates, Inc. Many of the
`designations used by manufacturers and sellers to distinguish their products are claimed
`as trademarks. Where those designations appear in this book, and O'Reilly & Associates,
`Inc. was aware of a trademark claim, the designations have been printed in caps or initial
`caps. The use of the hermit crab image in association with MP3 is a trademark of
`O'Reilly & Associates, Inc.
`
`While every precaution has been taken in the preparation of this book, the publisher
`assumes no responsibility for errors or omissions, or for damages resulting from the use
`of the information contained herein.
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`
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`Preface
` Conventions in This Book
` How to Contact Us
` Acknowledgments
`
`1. The Nuts and Bolts of MP3
` 1.1 MP3 Basics
` 1.2 Rights, Piracy, and Politics
`
`2. How MP3 Works: Inside the Codec
` 2.1 A "Perceptual" Codec
` 2.2 The Anatomy of an MP3 File
`
`3. Getting and Playing MP3 Files
` 3.1 Choosing and Using an MP3 Player
` 3.2 Players by Platform
` 3.3 Obtaining MP3 Files
` 3.4 Organizing Your Collection
` 3.5 Equipment Considerations
`
`4. Playlists, Tags, and Skins: MP3 Options
` 4.1 MP3 Options and Considerations
` 4.2 Equalization and Sound Quality
` 4.3 ID3 Tags and Playlists: The Virtual Database
` 4.4 Skins: Dressing Up MP3 Players
` 4.5 Plug-ins: Extending Your Reach
` 4.6 Listening to MP3 Streams
` 4.7 Performance Considerations
`
`5. Ripping and Encoding: Creating MP3 Files
` 5.1 General Encoding Principles
` 5.2 General Ripping Principles
` 5.3 Ripping and Encoding Tools
` 5.4 Ripping from Other Sources
` 5.5 Roll Your Own Compact Discs
`
`6. Hardware, Portables, Home Stereos, and Kits
` 6.1 Playing MP3 Through Your Home Stereo
` 6.2 Portable Players
` 6.3 Hand-Held Computers and Other Devices
` 6.4 Home Stereo MP3 Players
` 6.5 Car Players
` 6.6 Kit Players
`
`7. The Not-So-Fine-Print: Legal Bits and Pieces
` 7.1 The Rules of Engagement
` 7.2 The Players
`
`8. Webcasting and Servers: Internet Distribution
` 8.1 The Fundamentals of Internet Distribution
` 8.2 Offering Files for Download
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` 8.3 Webcasting: Real-Time MP3 Broadcasting
` 8.4 An Interview with MP3.com's "High Geek"
`
`9. Competing Codecs and Other File Formats
` 9.1 The Architectures
` 9.2 The Codecs
`
`A. Appendix: ID3v1 Genres
`
`Glossary
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`Preface
`
`This book has a simple premise: People want to build MP3 collections of the music they
`like and respect. To do justice to that music requires that the MP3 files constituting a
`personal music collection be of a high audio quality. But MP3 is generally considered to
`be a convenience format, not an audiophile format—its main advantages are its flexibility
`and its portability.
`
`While the press generally refers to MP3 audio as being "near CD quality," audiophiles
`often point to anomalies in the fidelity of the typical MP3 download. But there's a big
`difference between the average MP3 file downloaded from the Internet and a file you
`encode yourself, at a decent bitrate, from your own source material, using the encoder
`you feel yields the highest quality. MP3 is very much capable of achieving CD quality—
`you just have to pay a little attention to the variables. As I began to research the MP3
`scene in earnest, I found that only a small fraction of available resources were paying
`close attention to MP3 quality issues. As a hobbyist audiophile, I found this dissatisfying,
`and felt that it was important to provide readers with a "no-compromise" approach to
`MP3—you can have your convenience factors and a quality audio experience at the same
`time.
`
`While this book provides plenty of introductory material that will coach any reader
`through the basic mechanics of MPEG audio, it puts quite a bit of emphasis on fidelity
`issues, in addition to some of the peripheral topics not covered in depth in other books
`and online resources. Beyond the basics, for example, we'll be taking a close look at the
`many legal issues surrounding the MP3 scene, the challenges of building your own MP3
`playback hardware, the technical details involved in setting up your own MP3 streaming
`server, and more.
`
`It was also important to me that this book not be overly Windows-centric. Microsoft
`Windows may be king in terms of both the number of users and the number of MP3
`applications available, but I'm not convinced it's the best possible MP3 playback and
`creation platform, for reasons we'll go into elsewhere in the book. The number of MacOS
`users is increasing once again, Linux use is rising at an incredible clip, and BeOS is
`highly optimized for media content creation and consumption, with lots of built-in MP3-
`specific goodies. Accordingly, I've tried to balance coverage of non-Windows operating
`systems evenly throughout this book. Even if you use only one operating system, I hope
`you'll find reading about some of the alternative approaches illuminating.
`
`It practically goes without saying that the amount and variety of available MP3 playback
`and creation software is growing at an incredible rate, as are the number of MP3
`hardware options available. I don't pretend to have covered everything available in this
`book, and plenty of new applications and gear not covered here will undoubtedly be
`available by the time you read this. I've tried to structure the coverage of available
`products with an eye toward concepts, rather than specifics, so that the provided coverage
`will (hopefully) be applicable even to products that have yet to be invented. Please regard
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`the coverage in this book, even where application-specific, as a guide to MP3 creation
`and playback principles in general.
`
`MP3 is a truly amazing codec and a great feat of engineering. In conjunction with the
`huge array of "peripheral" technologies and tools available, MP3 has single-handedly
`ushered in a new era of file-based digital music distribution. It is my hope that this book
`will help you get the most out of the codec and its surrounding technology, so you can get
`back down to what this is all supposed to be about: enjoying the music you love.
`
`Conventions in This Book
`
`The following typographical conventions are used in this book:
`
`Constant width
`
`Indicates command-line elements, computer output, and code examples.
`
`Italic
`
`Introduces new terms and URLs, commands, file extensions, filenames, directory or
`folder names, and UNC pathnames.
`
`Indicates a tip, suggestion, or general note. For
`example, we'll tell you how to increase performance or
`save space, or we'll list links to useful web sites.
`
`
`
`
`
`Indicates a warning or caution. For example, we'll
`warn you about easy-to-overwrite traps, crucial plug-
`ins you should not delete, or where it is important to
`re-encode your material.
`
`
`
`
`
`
`
`How to Contact Us
`
`We have tested and verified the information in this book to the best of our ability, but you
`may find that features have changed (or even that we have made mistakes!). Please let us
`know about any errors you find, as well as your suggestions for future editions, by
`writing to:
`
`O'Reilly & Associates, Inc.
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`
`101 Morris Street
`
`Sebastopol, CA 95472
`
`(800) 998-9938 (in the U.S. or Canada)
`
`(707) 829-0515 (international/local)
`
`(707) 829-0104 (FAX)
`
`You can also send us messages electronically. To be put on the mailing list or request a
`catalog, send email to:
`
`info@oreilly.com
`
`To ask technical questions or comment on the book, send email to:
`
`bookquestions@oreilly.com
`
`We have a web site for the book, where we'll list examples, errata, and any plans for
`future editions. You can access this page at:
`
`http://www.oreilly.com/catalog/mp3/
`
`For more information about this book and others, see the O'Reilly web site:
`
`http://www.oreilly.com
`
`Acknowledgments
`
`As with any book of this scope, I did not work alone. I am much indebted to my editor,
`Simon Hayes, for helping to get this project off the ground and for his guidance in
`structuring and shaping this book in the "big picture." I am also most grateful for the
`many contributions made by our pool of technical editors:
`
`mp3tech.org's Gabriel Bouvigne, who possesses a nearly encyclopedic knowledge of
`MPEG's technical arcana and who helped to flesh out the details of this book in numerous
`ways.
`
`Lifelong audiophile Mike Knapp, who can build high-end amplifiers in his sleep and who
`contributed immeasurably to Hi-Fi issues throughout the book.
`
`Bruno Prior, who literally built a house around an extensive room-to-room home MP3
`network, and who seems to have used every MP3 tool on the planet extensively. Prior
`also contributed much on the topic of encoding from analog sources.
`
`MP3.com's "High Geek" Sander van Zoest, who offered much behind the scenes
`information, especially on the broadcasting and streaming side of things, and who turned
`me on to MP3 products and technologies before they happened.
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`In addition, I'd like to thank the members of the WinAmp, mp3stereo, SHOUTcast, and
`icecast mailing lists, as well as the community inhabiting various MP3 USENET groups.
`The following individuals have also offered assistance: John Hedtke, Malcolm Humes,
`Michael James, Henry Kingman, Bruce Lash, Marco Nelissen, Peter Urbanec, Rob
`Voisey, and Franc Zijderveld.
`
`This book is dedicated to my wife, Amy Kubes, who cheerfully put up with the endless
`stream of music (both good and bad) flowing from my office over the past year, and for
`her unwavering support during the course of this project.
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`Chapter 1. The Nuts and Bolts of MP3
`
`In April of 1999, the term "MP3" surpassed "sex" as the most-searched-on term at some
`of the Internet's top search engines—a phenomenal achievement for a complicated digital
`music encoding algorithm devised over the course of a decade by a few scientists and
`audiophiles in an obscure German laboratory.
`
`What is it about MP3 that inspires such unprecedented levels of enthusiasm? For some,
`it's the prospect of being able to store vast quantities of music on a computer's hard drive,
`and to shuffle and rearrange tracks from that collection around at a moment's notice. For
`others, it's the promise of an entirely new model for the music universe—one that allows
`creative artists to publish their own work without the assistance of the established
`industry. But for millions of users, the thrill of MP3 is more simple than that: it's the
`possibility of getting their hands on piles of high-quality music, free of charge.
`
`In this chapter, we'll get a bird's-eye view of the format and the MP3 phenomenon: what
`it is, how it works, how to download and create MP3 files, and how to listen to them.
`Then we'll take a look at some of the many issues surrounding MP3, including piracy,
`politics, digital rights, and the recording industry's stance on the matter. Finally, we'll
`examine the correlation between the MP3 and open source software movements, and find
`out why file-based digital music distribution is here to stay.
`
`1.1 MP3 Basics
`
`If you're new to the MP3 game, you'll want to know exactly what MP3 files are, where to
`get them, how they work, and how to make the most of a growing MP3 collection. As
`you read through this brief overview, keep in mind that these topics are covered in much
`greater detail elsewhere in this book.
`
`1.1.1 What Is MP3?
`
`Simply put, MP3 is an audio compression technique. Raw audio files—such as those
`extracted from an audio CD—are very large, consuming around 10 MB of storage space
`per minute. But MP3 files representing the same audio material may consume only 1 MB
`of space per minute while still retaining an acceptable level of quality. By drastically
`reducing the size of digital audio files, it has become feasible for music lovers to transfer
`songs over the Internet, for users to build enormous digital music collections on their
`hard drives, to play them back in any order at any time, and to move them around
`between different types of playback hardware. These possibilities have far-reaching
`ramifications not just for music lovers, but for artists and the recording industry as well.
`We'll explore the politics and philosophical issues raised by MP3 in the second part of
`this chapter.
`
`1.1.1.1 Why the term "MP3?"
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`"MP3" is the quick way of referring to an encoding algorithm called "MPEG-1, Layer
`III," developed primarily by a German technology group called Fraunhofer and Thomson
`and now officially codified by the International Standards Organization, or ISO. The
`name, of
`course,
`corresponds
`to
`the
`extension
`found on MP3
`files:
`After_the_Goldrush.mp3, for example. More on Fraunhofer and Co. can be found in
`Section 1.1.3 later in this chapter.
`
`1.1.1.2 Small is beautiful: How MP3 works
`
`Raw audio does not compress well via traditional techniques: if you try to zip up a WAV
`file, for instance, you'll find that the resulting archive is only marginally smaller than the
`uncompressed original.
`
`MP3 takes a different tack on the compression problem. Rather than just seeking out
`redundancies like zip does, MP3 provides a means of analyzing patterns in an audio
`stream and comparing them to models of human hearing and perception. Also unlike zip
`compression, MP3 actually discards huge amounts of information, preserving only the
`data absolutely necessary to reproduce an intelligible signal. The amount of data
`preserved is configurable by the person doing the compressing, so an optimal balance
`between file size and quality can be achieved. The tool or software used to achieve the
`compression is called an "encoder," while the playback software is called a "decoder" or,
`more simply, an "MP3 player."
`
`By running uncompressed audio files through an MP3 encoder, files can shrink to around
`one-tenth of their original size, while still retaining most of their quality. By compressing
`a little less (to around one-eighth of the original size), MP3 quality can be virtually
`indistinguishable from that of the original source material. As a result, a three-minute
`song can be transformed into a 3 MB file, which is something most people can find room
`for on their hard drives, and that most web surfers can download in a reasonable time
`frame. In other words, a 640 MB compact disc stuffed full of MP3 files rather than
`uncompressed audio can store around 10-11 hours worth of music. And since DVDs store
`around eight times as much as compact discs, a recordable DVD could hold nearly five
`days worth of continuous music on a single 5" platter.
`
`The mechanics of the MP3 codec and perceptual encoding principles can be found in
`Chapter 2.
`
`1.1.2 Working with MP3 Files
`
`If you know how to download files from the Internet, have a grasp of basic file
`management concepts, and aren't afraid to experiment with new applications, you can
`probably get started on your own MP3 collection without much coaching. However, there
`are a lot of options and considerations to take into account, including the quality and
`efficiency of MP3 encoders and players, advanced features and functions, techniques
`used for organizing and customizing large MP3 collections, and so on. We've dedicated
`all of Chapter 3, and Chapter 4, to these topics. For now, here's a brief tour of the
`basics.
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`1.1.2.1 Downloading MP3s
`
`
`
`In order to start playing MP3 files, you'll need to get your hands on some, of course.
`There are two ways to do this: You can either download MP3s that other people have
`created, or you can create them from the music you already own.
`
`
`
`Before you start downloading MP3s, you should know that the vast
`majority of files available out there are distributed illegally. Many
`people encode music they legally own, and then make it available on
`the Internet to people who do not own that music, which is illegal
`(see Chapter 7, for more information). Whether you choose to
`download pirated music is a moral choice that only you can make.
`The wide availability of pirated music, however, should not stop you
`from seeking out legal MP3s. While there are far fewer of these
`available, you'll be surprised by the quality of the gems you'll find
`hiding out in the haystacks. A great place to find legal MP3s is
`MP3.com, though that site is certainly not the only source of
`legitimate files. If you use a commercial MP3 tool like RealJukebox
`(Chapter 3), you'll probably find a button or link in the interface
`that will take you directly to an MP3 download site.
`
`
`
`1.1.2.2 Finding MP3 files
`
`While most users start out by simply typing "MP3" into their favorite search engine, that
`probably isn't the most efficient way of going about things. You might want to start
`instead at a major site dedicated to indexing or distributing MP3 files, such as
`http://www.mp3.lycos.com,
`http://www.listen.com,
`http://www.scour.net, or http://www.rioport.com. Search engines can,
`however, be very useful for finding smaller sites run by individuals—but be prepared to
`encounter lots of broken links and unresponsive sites. Because many user-run sites are
`quickly shut down by Internet Service Providers (ISPs) under pressure from record labels,
`search engines often index links to sites that no longer exist.
`
`The Web isn't the only way to find MP3 files—you'll also find plenty of files on FTP
`servers, in binary Usenet groups, and in IRC channels. Details on using these venues for
`MP3 downloading can be found in Chapter 3 and Chapter 4.
`
`
`
`Users looking to swap MP3 files easily with music fans all over the
`world
`may
`want
`to
`check
`out
`Napster
`(http://www.napster.com), which is a sort of combined IRC,
`FTP, and search client with a twist. Rather than searching the Web,
`you'll be searching the hard drives of other Napster users for songs
`you like. Since you'll only see files on the systems of people
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`currently using the service, you won't have to worry about broken
`links and downed servers. Log in to the Napster server, register your
`collection with a specific genre, and you'll be able to search for files
`on other people's systems by song name or artist. Find a song or
`songs you like and transfer them to your hard drive, while other
`people do the same with your music collection. Meanwhile, you can
`chat with other music lovers in the background as your transfer
`proceeds. Great idea, but the potential for copyright abuse inherent
`in this product is extreme, and none of the music we found during
`testing was legitimate. Nevertheless, Napster has single-handedly
`ushered in a whole new era of user-to-user file sharing, and has the
`music industry more worried than ever.
`
`
`
`1.1.2.3 Creating your own MP3 files
`
`Creating your own MP3s is only slightly more difficult than downloading them, but the
`payoff is worth it. You know for a fact that the music in your collection is the music you
`like, you can personally control the quality of the encodings, and you don't have to worry
`about whether any of your tracks are illegal.
`
`Encoding tracks from your CD collection is a two-step process. First, bits from an audio
`CD must be transferred to your system as uncompressed audio, typically as a WAV file.
`This extraction process is known as ripping . The uncompressed audio is then run
`through an MP3 encoder to create an MP3 file. However, there are dozens of tools
`available that take care of all the hard work behind the scenes, ripping and encoding
`transparently in a single step. You'll meet a handful of ripper/encoder combination tools
`in Chapter 5.
`
`1.1.2.4 Playback basics
`
`Think of an MP3 file like any other document you might store on your computer and
`open in an application. You can open a document by using an application's File Open
`menu, by double-clicking a document icon, or by dragging a document onto the
`application's icon. MP3 files are no different, and can typically be played in any of these
`ways. There are hundreds of MP3 players available for virtually all operating systems,
`and all of them are capable of playing all MP3 files. As a user, you have tons of options
`when it comes to picking your tools. In Chapter 3, you'll meet some of the most
`popular MP3 players available for Windows, MacOS, Linux, and BeOS, and be
`introduced to the fundamental principles of MP3 playback.
`
`1.1.2.5 Playlists
`
`One of the most liberating aspects of working with file-based music (as opposed to music
`stored on media such as CDs, tapes, or LPs) is the fact that you suddenly gain the ability
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`to organize, randomize, and mix the tunes in your music collection in an infinitude of
`ways. If you've ever created custom mixed-music cassette tapes, you know how fun—and
`how time consuming—this can be. MP3 playlists let you enjoy the fun part while
`skipping the time-consuming part.
`
`The vast majority of MP3 players include a "playlist" window or editor, into which you
`can drag any random collection of tracks. Any playlist can be saved for posterity, to be
`played again at a later date. A playlist can be as short as a single song or as long as your
`entire collection (some people have playlists referencing months of nonrepeating music).
`A playlist can reference all the music in a folder or an entire directory structure, or can be
`composed by querying your system for all songs matching a certain criteria. For example,
`you can create playlists of all country music written prior to 1965, or all of your acid jazz
`tracks, or all of your schmaltzy disco. Playlist creation and manipulation is covered in
`detail in Chapter 4.
`
`
`
`Playlists are simple text files listing references to the actual locations
`of MP3 files on your system or on a network. As such, they consume
`almost no disk space. Because playlists reference songs on your
`system, it is usually not useful to trade them with other users. There
`are, however, playlists comprised only of URLs to MP3 files on the
`Internet, and these will, of course, work on anyone's system.
`
`
`
`
`
`1.1.2.6 ID3 tags
`
`MP3 files are capable of storing a certain amount of "meta-data"—extra information
`about each file—inside the file itself. Data on track title, artist, album, year, genre, and
`your personal comments on the track can all be stored in an MP3 file's ID3 tags. These
`tags will be inserted automatically by most tools as you rip and encode, or can be added
`or edited later on, often directly through your MP3 player's interface. ID3 tags become
`more important as your collection grows, especially when you start using database-
`oriented MP3 organizers, as described in Chapter 4.
`
`1.1.2.7 Internet radio
`
`Some people have neither the time nor the inclination to create and manage a huge MP3
`collection. Fortunately, they don't have to. Thanks to the rise of outfits like SHOUTcast
`(http://www.shoutcast.com) and icecast (http://www.icecast.org), thousands
`of users are streaming MP3 audio from their computers to the Internet at large, running
`live broadcasts much like a radio station. There are several key differences between MP3
`downloads and MP3 streaming:
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`MP3 broadcasts aren't saved to the listener's hard disk, unlike MP3
`downloads. When you tune in to a broadcast, the only thing that's
`saved to disk is a tiny text file containing some meta-data about the
`broadcast in question, including the server's address and a playlist.
`This file is passed to the MP3 player, which in turn receives and
`handles (buffers) the ongoing broadcast.
`
`Broadcasts are synchronous, while downloads are asynchronous. In
`other words, when you tune in to a broadcast, you hear exactly what's
`being played from a given server at that moment in time, just like the
`radio. When you download a file, you get to listen to it any time you
`want.
`
`Because of bandwidth constraints on most listeners, broadcasts are
`typically of a lower fidelity than MP3 downloads. MP3 broadcast
`servers usually send out MP3s that have either been down-sampled to
`a lower frequency, encoded at a lower-than-normal bitrate, or sent as
`a mono rather than stereo stream.
`
`Full details on tuning in to MP3 broadcasts can be found in Chapter 4. The process of
`running your own Internet radio station is described in Chapter 8.
`
`1.1.2.8 Beyond the computer
`
`While you'll almost certainly create all of your MP3 files on your computer, and will
`most likely begin your MP3 explorations by playing them back through your computer as
`well, part of the magic of file-based digital audio is the flexibility. There's no reason an
`MP3 file can't be transferred to any device that includes a storage and playback
`mechanism. And sure enough, a whole new class of devices has arisen to meet this need:
`portable units similar to the classic Sony Walkman but geared for MP3 playback, rather
`than tape or CD, are becoming hugely popular. Meanwhile, we're beginning to see the
`emergence of a whole new range of home stereo MP3 components, capable of storing
`gigabytes of digital audio and being operated just like any other home stereo component.
`Of course, the technology is being applied to car stereos as well. Even hand-held
`computers such as the Handspring Visor are gaining MP3 playback capabilities.
`
`Users with some technical know-how and a soldering iron are hacking out techniques for
`building MP3 playback hardware of their own, free from SDMI and other security
`mechanisms (see Chapter 7 for more about MP3 security and legal issues) that
`ultimately limit the functionality of commercial MP3 hardware. Chapter 6, includes
`comparative analysis of MP3 portables, an early look at a few MP3 home stereo
`components, and introduces the concepts of building your own MP3 hardware from
`scratch.
`
`1.1.3 About the Codec
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`So, what exactly is MPEG audio compression, and MP3 specifically? Technically, that's
`a bit of a long story, so we'll go into great detail on that in Chapter 2. You don't need to
`know how MP3 works in order to start playing with it, but to shed a little light on the
`subject now, MPEG audio compression is a "psychoacoustic" technique that exploits
`various limitations in both the human ear and the mind's ability to process certain kinds
`of sounds at very high resolutions. MPEG encoders store "maps" of human auditory
`perception in a table, and compare an incoming bitstream to those maps. The person
`doing the encoding gets to specify how many bits per second will be allocated to storing
`the final product. Taking note of that restriction, the encoder does its best to strip away as
`much data as possible (within the specified data storage limitation, or "bitrate") while still
`retaining the maximum possible audio quality. The more bits per second the user allows,
`the better described the final output will be, and the larger the resulting file. With fewer
`bits per second, the user will get a smaller file (better compression), and a corresponding
`decrease in audio quality. Again, we'll go into the process in greater detail in Chapter 2.
`
`1.1.3.1 The MPEG family
`
`MPEG is not a single standard, but rather a "family" of standards defined by the Moving
`Picture Experts Group, which was formed in 1998 to arrive at a single compression
`format for digital audio and avoid a standards war between various competing
`technologies. All of the MPEG standards are used for the coding of audio-visual data into
`compressed formats.
`
`
`
`Coding in this sense of the word refers to the process of running a
`stream of bits through an algorithm, or set of rules. Encoding is the
`process of taking an uncompressed bitstream and running it through
`the algorithm to generate a compressed bitstream or file. Decoding
`is, naturally, the opposite—taking a compressed bitstream and
`turning it into an uncompressed file or an audible signal. The term
`codec is short for compressor/decompressor,[1] and refers to any
`algorithm capable of performing this bidirectional function.
`
`[1] In some circles, the term stands for enCOder/DECoder, though
`this interpretation has lost favor to compressor/decompressor.
`
`
`
`The MPEG family is broken down into major classes (MPEG-1, MPEG-2, MPEG-4),
`which are further broken down into sub-classifications called layers . Each major class
`and layer is optimized for specific real-world applications, such as compressed movie
`soundtracks, broadcast, or file-based musical coding. Each successive layer is more
`complex than the preceding layer. For example, a layer III decoder will be 2.5 times more
`complex than a layer I decoder. The MPEG "layers" are described in sub-documents of
`each class, with audio coding schemes described in a document labeled "ISO/IEC11172-
`3." The MPEG coding technique that interests us in this book is MPEG-1/MPEG-2 Layer
`III, referred to throughout this book simply as "MP3."
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`Technically, MPEG-1 Layer III and MPEG-2 Layer III are both
`referred to as MP3, as are the rather obscure MPEG 2.5 extensions.
`MPEG-1 Layer III is used for 32, 44.1, and 48kHz sampling rates,
`while MPEG-2 Layer III is for 16, 22.05, and 24kHz sampling rates.
`The MPEG 2.5 extensions allow for 8 and 11kHz. MP3 players can
`play any of these, and the specs are very similar.[2] The vast majority
`of files you'll encounter in the wild are simple MPEG-1 Layer III.
`
`[2] MPEG-2 also allows for multichannel extensions of up to five
`channels, though few people have ever actually seen this in action.
`Multichannel efforts are concentrated on MPEG-4, covered in
`Chapter 9.
`
`
`
`Do not confuse MPEG-1 Layer III (MP3) with MPEG-3—there is no such animal. There
`was once an MPEG-3 classification in development, which was intended to address high-
`quality video. However, MPEG-2 was shown to deliver sufficiently high quality, so
`MPEG-3 was conjoined with the existing MPEG-2 specification. The spec now skips
`from MPEG-2 to MPEG-4.
`
`1.1.3.2 The MP3 patent
`
`The fact that the MP3 spec is maintained by the MPEG Working Group doesn't mean
`they invented the technology. The working group merely codifies standards to guarantee
`interoperability between various applications, operating systems, and implementations.
`One of the very first tasks of the working group was to circumscribe the conditions of the
`ownership of intellectual property under the umbrella of international standards. Their
`conclusion was that patented technologies are allowed to be codified as standards, but
`that those patents must be fairly and equitably licensable to all comers, so that no single
`company could gain a monopoly on a specific audio/video compression technology.
`
`The MP3 codec itself was devised by the Fraunhofer Institute of Germany and