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Believe it or not, the world of audio actually extends beyond iTunes and the iPod. When you’re facing well over a hundred audio-file formats (if you don’t believe us, see www.sonicspot.com/guide/fileformatlist.html and be amazed), understanding the world of digital audio may seem more than a tad overwhelming. Here’s a first step in comprehending the clouded mysteries of the digital-audio world.
Popular Audio File Formats
.AAC Advanced Audio Coding File was declared the new audio-file standard in 1997, designed to replace its predecessor, MP3. It provides better quality at lower bit rates, and it’s Apple’s standard iTunes and iPod audio format.
.AIF(F) Audio Interchange File Format was developed by Electronic Arts and Apple back in the ’80s. AIFF files contain uncompressed audio, resulting in large file sizes.
Apple Lossless This file format uses lossless compressions (see the definition under the Important Terminology section) for digital music. Since it stores data in a MP4 container, it has an .m4a file extension.
.MID(I) MIDI is not a true audio-file format; rather, it’s a music-device-controlling protocol to control instruments using computers - and vice versa - in real time.
.MP3 MPEG Layer 3 is the most popular digital-audio music format, designed by a team of European engineers in 1991 to conserve the quality of a song while presenting it in a small, compact file.
.OGG Ogg Vorbis compressed audio file is one of the most popular license-free, open-source audio-compression formats. It’s efficient for streaming and file compression because it creates smaller files than MP3 while maintaining audio quality. Unfortunately, an unhacked ’Pod can’t play OGG files.
.RA(M) Real Audio Media was developed by RealNetworks in 1995. It has a wide variety of uses, from videos to music, but is mainly used for streaming audio such as that from Internet radio stations.
.WAV Windows WAVE sound file is a an IBM- and Microsoft-developed format popular among PC computer users; it can hold both compressed and uncompressed audio.
.WMA Windows Media Audio was designed by Microsoft to be an MP3 competitor, but with the introduction of iTunes and iPods, it’s fallen far behind MP3 in popularity.
Popular Video File Formats
.FLV Flash Video Format was developed by Macromedia, and is used to deliver video over the Internet (it's the format used by YouTube). It requires the Adobe Flash Player for viewing.
H.264 MPEG-4 Part 10 is a digital video codec standard based on MPEG-4 used to get high data compression while maintaining good image quality.
.MOV QuickTime File Format is a multimedia container file that containers audio and video tracks. The video and audio may be encoded using one of several different QuickTime-supported codecs.
.MP4 and .M4V MPEG Layer 4 is a popular video format defined by the Moving Picture Experts Group. It became a standard in 2000 and was included in QuickTime in 2000.
.MPV MPEG Layer 1 was developed in 1993 by the Moving Picture Experts Group. It's often used with Video CDs (VCDs).
.WMV Windows Media Video is a format developed by Microsoft. Other Windows Media Video formats include .ASF, .AVI, or .MKV.
BIT RATE A song’s bit rate is a measurement of the amount of data being transmitted or processed. As a song is played back or recorded, there is a transfer of data, measured in kbps (kilobits per second; a kilobit is one thousand bits). As the bit rate increases so does the quality of the song. For example, although 128kbps is considered to be the standard for MP3s in terms of quality versus file size, an MP3 file encoded at 192kbps may sound noticeably better.
CODEC An acronym for compression/decompression. Codecs are components - either hardware or software - which compress the size of a media file during saving and decompress the file during playback.
DRM Also known as digital rights management, these copy-protection schemes are used by music distributors such as Apple’s iTunes Music Store to restrict their songs from being played on other computers or digital-music devices.
FAIRPLAY Apple’s form of DRM, which prevents “unauthorized” computers and non-iPod digital music players from playing songs bought from the iTunes Music Store.
ID3 TAG In MP3 files, the ID3 tag allows song information such as the title, artist, album, track number, and so on to be stored in the file itself.
LOSSLESS COMPRESSION This type of codec allows file compression while keeping all of the file’s original quality. Some examples are the Apple Lossless Encoder, FLAC, and the common file-compression format known as ZIP.
LOSSY COMPRESSION This type of codec discards some data in order to make songs small - usually, however, the drop in quality due to the discarded data is not noticeable except to the most discerning ear. MP3, JPEG, and Ogg Vorbis are all lossy-compression formats.
MONO Short for monophonic, a mono audio system pumps all the sound through only one channel - even if you have multiple speakers connected to your audio source, you’ll hear the same sound from each of your speakers.
PLAYSFORSURE Microsoft's form of DRM. iPods and iTunes cannot play music encoded with Microsoft's DRM.
SAMPLE RATE A digital audio file’s sample rate indicates how many times the signal was measured when it was converted from an analog signal to a digital one. Sample rates are measured in Hz, and as the sampling rate increases so does the audio quality. Also note that to maintain sound quality, the sampling rate must be twice the original audio’s highest frequency. The standard CD and MP3 sample rate is 44.100kHz.
STEREO Short for stereophonic, a stereo audio system distributes sound through two separate channels, left and right. The amount of the same sound coming from the two speakers determines where that sound appears to be coming from in the stereo field; a sound coming from only the left speaker, for example, sounds as if it’s coming from - you guessed it - only the left, while an equal amount of a sound coming from both speakers appears to be emanating from the middle of the stereo field.
SURROUND SOUND Sound distribution that involves multiple channels (ranging from three to ten) to create a sense of realism. For example, some DVD movies have audio tracks that can use five different channels.