Glossary

AAC (Advanced Audio Coding): Also called MPEG-4 AAC, this audio codec is the continuation of the MP3 codec created by Fraunhofer-Gesellschaft. Due to advances in the technology, AAC files encoded at a 96 kbps bit rate sound slightly better than MP3s encoded at 128 kbps.
ADPCM (Adaptive Differential Pulse Code Modulation): This method of encoding sound data files takes up less storage space than the regular PCM format used by WAV and AIFF files--and CD audio for that matter. ADPCM comes in more than one flavor: IMA's ADPCM, for example, is used on the Sony MiniDisc to cram more data onto a smaller platter; Microsoft's ADPCM is used as part of Windows canon of audio codecs. Many MP3 players use ADPCM for their voice-recording feature.
AIFF: An uncompressed Macintosh audio format, functionally identical to Windows' WAV. Uncompressed, sound files occupy a huge amount of disk space, thus the need for compressed formats, such as MP3.
album: A collection of tracks, usually 10 songs or so.
ATRAC: Sony's audio codec used by MiniDisc players. It involves dropping all frequencies below and above the human hearing range (20Hz to 20KHz).
ATRAC3: Sony's audio codec used by MDLP MiniDisc players and Sony portable players. It allows twice the data compression of ATRAC.
audio compression: Audio compression works by setting a limit for how loud sound can get while raising low parts of a song a certain extent, depending on the level of compression. Basically, the lowest and highest volume levels of a song get closer together.
bit rate: A measure of how many bits of information describe each sound in an audio file. A low bit rate means lower quality and a smaller file size, while a high bit rate means better quality and larger files.
CDA (Compact Disk Audio): The format of audio on a standard RedBook CD; can be extracted to your hard drive by a ripper into WAV (Windows) or AIFF (Macintosh) files.
Codec: An algorithm for compressing and decompressing the data that makes up audio and video files. Once a file has been compressed by a codec like MP3 or RealAudio, it is smaller and easier to transmit across the Web, and, in most cases, still sounds fairly true to the original.
CBR (Constant Bit Rate): A method of encoding the music from the CD at a fixed number of bits throughout the song. It pays no attention to the music levels it is encoding.
DAC (Digital-to-Analog Converter): A circuit that turns the digital 1s and 0s representing a sound to an analog waveform (which, in turn, is usually amplified and turned into audible sound).
Digital music service: A provider of online music that sells tracks and albums (like a store), a subscription to streaming audio (typically on-demand streaming), or a hybrid of the two. Some services also offer premium radio and CD burning. Music is delivered using a software application (usually as part of a media player), or a standard Web browser. See the Digital Music Services section of our Tech Guide for up-to-date information about each of the major services.
DRM (Digital Rights Management): A variety of systems that enable the copyright owner of a piece of intellectual property (such as music, video, or text) to specify what someone else can do with it. Typically, this is used to offer downloads without having to worry that the user is freely distributing the file over the Web without any compensation to the copyright holder.
DSP (Digital Signal Processing): The (usually real-time) processing of an audio signal in such a way that it sounds different from the original. Examples include: bass boost; 3D simulation; and Rock, Jazz, and Classical presets.
DVD-R (Digital Versatile Disk): DVD-R Probably one of the most common DVD formats and accepted by the widest number of DVD players on the market.
Encoder: Software that turns uncompressed WAV (Windows) or AIFF files into compressed files, using a CODEC such as MP3 or RealAudio.
FLAC: A codec similar to MP3, but "lossless" in that it completely preserves a file's audio fidelity (at the price of a larger file size than "lossy"). FLAC is free and its source code is open, so users and developers are able to view code and extend its functions.
flash player: A portable player that stores songs on a solid state chip. This has many advantages over hard drives, except that it is much more expensive per megabyte. With capacities ranging from 32MB to 1GB, flash players won't store thousands of songs. But because they have no moveable parts, they're small, don't skip even during jarring impact, and make batteries last significantly longer than other types of MP3 player.
hard drive player: A portable player that stores songs on a hard drive disk, as opposed to flash memory. They range in size from 1GB to 80GB and (potentially) upwards. The advantage is mainly the cheap, massive storage capability allowed by these drives, which are typically 1.8" or smaller in diameter. The disadvantage is that a hard drive contains movable parts, and as such is susceptible to knocks, and general wear. Hard drives also slower to load music than flash memory, and use more battery power.
ID3: A "tag" or collection of data, embedded in MP3 files, which identifies the song with information like artists, title, album and genre. These tags can be edited.
ID3v2: An updated and expanded version of ID3 tagging that allows much more data.
Jukebox: A multipurpose audio program that usually incorporates an audio player, a ripper, an encoder, and a file organizer.
Liquid Audio: A company (and a file type) that offers a proprietary combination of digital rights management and compressed audio.
Lossless: A method of file compression in which audio data is not permanently discarded. While keeping all of a song's information results in a much bigger sound file, if preserving full audio fidelity is of highest importance, this is the way to go.
Lossy: A type of file compression in which audio data is thrown away, or lost, as a way of shrinking file size. MP3, for instance, is a lossy format, but, like other lossy formats, tries very hard to discard only data that is not usually heard.
M3U: When you create a playlist in some media players, like Winamp, the playlist file contains the extension M3U. Clicking an M3U file will bring up all of the songs in the playlist in your default audio player.
MDLP (Minidisk Long Play): (Minidisk Long-Play) - A method for doubling or quadrupling the amount of audio that a MiniDisc can hold, using ATRAC3 compression.
Media player: A program that allows you to play and manage audio and video files. Some programs also offer ripping, burning, and visual effects. Examples include: iTunes, Winamp, Windows Media Player, Sonique, Quintessential, Musicmatch Jukebox.
MP3: Short for MPEG-1, Layer 3, this is a codec that, for a number of reasons, became the most popular format for digital music as its popularity hit critical mass. Now, "MP3" is commonly used as shorthand for any type of digital music file.
MP3 player / device: Hardware or software device for playing audio files encoded using MPEG1 layer 3 (mp3).
MPEG (Moving Pictures Experts Group): Created by a working group of the International Standards Organization, MPEG is a standard for compressing sound and movie files into an attractive format for downloading--or even streaming--across the Internet. The MPEG-1 standard streams video and sound data at 150 kilobytes per second--the same rate as a single-speed CD-ROM drive--which it manages by taking key frames of video and filling only the areas that change between the frames.
OGG (Ogg Vorbis): This is an open-source codec, meaning (among other things) that no one has to pay licensing fees when it's used, unlike proprietary codecs such as MP3, WMA, or AAC.
playlist: A list of songs for playback that can include CD audio, MP3s, WMAs, or any other kind of audio file. Playlists can be randomized to create a mix and saved to hard drives and CD-Rs.
portable player: A physical device for playing audio, such as an iPod or Rio, small enough to be carried around.
RA (Real Audio): A codec created by Real, mainly used for streaming audio using the RealPlayer software. This format has been around since 1995, and has many users, particularly for song samples, live events, and lower-fidelity audio such as radio shows.
RAX (RealAudio 10): The latest version of the RealAudio format, used for both streaming and downloading. At low bit rates, RealAudio 10 uses the same high-compression codecs as previous versions of RealAudio, but above 128 kbps switches to AAC, allowing for better fidelity and compatibility with AAC-enabled players. The file extension for RealAudio 10 is .rax.
RedBook CD: A CD filled with uncompressed audio in the CDA format used by CD burning software in the audio mode; also, the type of CD you buy in stores.
sampling rate: The precision with which a digital file describes the analog sound it represents. Basically, a lower rate produces files that sound worse and take up less drive space than those with a higher rate. CDs have a sampling rate of 44.1 kHz, and DAT machines have a sampling rate of 48 kHz. MiniDisc player/recorders with a built-in sampling rate converter can handle both rates.
Sound card: A piece of circuitry added to your computer that allows it to play and record sound. Sound cards have outputs on the back in a variety of formats that enables sound to travel to headphones, speakers, stereos, MiniDisk players, and so on. Typically, sound cards accept and emit analog signals, but some specialized sound cards handle digital input and output.
SBR (standard bit rate): The standard type of compression wherein an entire audio file is encoded at the same bit rate, as opposed to variable bit rate encoding.
stereo: Two channels of audio. When you listen to something in stereo, different sounds come out of the left and right speakers or headphones. Since stereo tracks contain twice the information of an equivalent mono file, they are twice the size.
Track: A piece of audio, such as a song.
USB (1.1 or 2.0): MP3 players that support USB (Universal Serial Bus) 1.1 are compatibly with a wide range of computers, since most Mac, Windows, and Linux machines support it. Newer Windows and Linux machines tend to support USB 2.0, which transfers files at much faster speeds - great for syncing music to a high-capacity hard drive player.
(VBR) variable bit rate: A method of compressing and encoding audio at a bit rate optimized for each section, or "frame," of sound, depending on the part's complexity. This allows for high fidelity, while helping to keep file size down.
WAV: An uncompressed Windows audio file, equivalent to AIFF in Mac OS. WAV files occupy a large amount of disk space, thus the need for compressed formats, such as MP3.
WMA (Windows Media Format): The Windows Media Player format, which (according to independent testing) sounds as good as MP3 at half the bit rate (and therefore half the file size).