AUDIO FILE FORMAT Kalpita Potawad M.L.I.SC 2012-2013
CONTENT Definition History Types Audio file formats extensions Advantages and Disadvantages of audio file format Three categories Examples
DEFINITIONAn audio file format is a file format forstoring digital audio data on a computersystem. This data can be storeduncompressed, or compressed to reducethe file size. It can be a raw bitstream, butit is usually a container format or an audiodata format with defined storage layer.
HISTORYPhonographIn the early 19th century, it was allbut impossible to imagine whatgreat changes were in store for theworld of audio. Although the firstsuccessful recording device wasdeveloped in 1855, it wasnt untilThomas Edisons phonograph(invented in 1877) and EmileBerliners Gramophone (patented in1887) that the phonograph startedto come into its own.
RADIOIts hard to imagine a world without radio,but the technology has only been aroundsince the 1920s.The theoretical basis ofthe propagation of electromagnetic waveswas first described in 1873 by JamesClerk Maxwell in his paper to the RoyalSociety A dynamical theory of theelectromagnetic field, which followed hiswork between 1861 and 1865.
8-TRACKInvented in the early 1960s by WilliamPowell Lear, and heavily marketed and usedin the 70s, the 8-track was the premierportable audio format for almost 15 years.The 8-track was designed around a single reelwith the two ends of the plastic recordingtape joined with a piece of conductive foiltape to make one continuous loop.
CASSETTE TAPE The cassette as we know it didnt come into the average home until the late 1970s. However, magnetic tape recording got its start in music studios around 1950. Musicians could record in longer sessions, and seamless splice editing allowed artists and producers to select and combine the best cuts into polished songs. The allure of magnetic tape as a recording medium blossomed.
COMPACT DISCA compact disc (or CD) is an optical disc used forstoring digital data. It was originally invented fordigital audio and is also used as a data storagedevice, a CD-ROM. CD-ROM reading devices arefrequently included as a component in personalcomputers. In general, audio CDs are distinctfrom CD-ROMs, and CD players intended forlistening to audio cannot make sense of the dataon a CD-ROM, though personal computers cangenerally play audio CDs.
DIGITAL AUDIO TAPES (DAT) Introduced in 1987 for the studio market, digital audio tapes quickly became de rigueur in professional recording industry circles. Although DATs never fully caught on in the consumer market because of the high cost of DAT players, they remain a mainstay of the pro-audio world because of their low price and enhanced digital storage capabilities. Another factor helped keep DATs from catching on with consumers: A tax was added to each tape sold, earmarked to compensate music companies for songs that could be pirated. Most DAT users today use computer- grade DAT tape to circumvent the tax.
MINIDISC MiniDisc (MD) is a disc-based data storage device for storing any kind of data, usually audio. The technology was announced by Sony in 1991 and introduced January 12, 1992. MD Data, a version for storing computer data was announced by Sony in 1993, but it never gained significant ground, so today MDs are used primarily for audio storage. The audio discs can be premastered or recordable (blank).
MP3 Invented in 1989 in Erlangen, Germany, MP3 has quickly come to symbolize a paradigm shift in the way many people access their music. The home computer revolution, along with the Internet, has allowed millions of Net- connected music fans to take advantage of the latest audio medium. AACAAC is a new audio compression technology, AdvancedAudio Coding. This new standard, developed by Dolby, theFraunhofer Institute, and others, may become the majoringredient in 21st century digital music distribution. TheAAC codec was formally introduced to the world at theConsumer Electronics Show 2001, along with dozens ofnew digital audio players able to play AAC files.
TYPES There are three major groups of audio file formats: Uncompressed audio formats, such as WAV, AIFF, AU or raw header-less PCM; Formats with lossless compression, such as FLAC, Monkeys Audio (filename extension APE), WavPack (filename extension WV), TTA, ATRAC Advanced Lossless, Apple Lossless (filename extension m4a), MPEG-4 SLS, MPEG-4 ALS, MPEG-4 DST, Windows Media Audio Lossless (WMA Lossless), and Shorten (SHN). Formats with lossy compression, such as MP3, Vorbis, Musepack, AAC, ATRAC and Windows Media Audio Lossy (WMA lossy)).
AUDIO FILE FORMATS EXTENSION.mid MIDI (Musicl Instrument Digital Interface).wav Waveform Extension.aif Audio Interchange Format Motion Picture Expert Group Audio -.mp2 also referred to as MPEG-1 layer-2 or.mp3 MPEG-1 Layer-3.ra.ram Real Audio.rpm
ADVANTAGE AND DISADVANTAGE OF AUDIO FILEFORMATS The following is a list of the more common audio file formats along with the advantages and disadvantages of each for Web design.
.MID Wide support in many browsers with no need for a plugin. They can have very good sound quality, but this can vary somewhat with the quality of the sound card. Very small file size for a lengthy selection. The files are instrumental only. The files can not be recorded. They must be synthesized on a computer with special hardware and software.
.WAV Very good sound quality. Widely supported in many browsers with no need for a plugin. You can record your own .wav files from a CD, tape, microphone, etc. The very large file sizes severely limit the length of the sound clips that you can use on your Web pages.
.AIF Very good sound quality. Widely supported in many browsers with no need for a plugin. You can record your own .aif files from a CD, tape, microphone, etc. The very large file sizes severely limit the length of the sound clips that you can use on your Web pages.
.MP2/.MP3 This is a compressed format which makes the sound files substantially smaller. The sound quality is very good. If an MP3 file is recorded and compressed properly, the quality can rival that of an actual CD. New technology is emerging that will allow you to "stream" the file so that the audience doesnt have to wait for the entire file to download before they can hear it. The file size is still larger than a Real Audio file and a whole song would still take quite awhile to download over a normal phone line connection. Your audience must download and install a helper application or plugin to hear the sounds.
.RA/.RAM/.RPM Very high degree of compression with smaller file sizes than .mp2 or .mp3. Whole songs files are reasonable to download. The files can be "streamed" from a normal Web server without any special software so that the audience can begin listening to the sound before the file has completely downloaded. Whole songs will start paying within seconds over normal phone line connections. The sound quality is poorer than the quality of the .mp2 or .mp3 files, but the new G2 player and encoder have increased the quality considerably. Your audience must download and install a helper application or plugin in order to appreciate the excellent quality of the new G2 standard. However, browser manufacturers are beginning to include a plug-in for the older version 5 player with the browser downloads.
THREE CATEGORIES Uncompressed audio formats A WAV audio file is an example of an uncompressed audio file. Lossless compression The WMA audio file format uses lossless compression. Lossy compression MP3 and Real Audio files use a lossy compression.
EXAMPLE Example 1: audio-info (content): A song called "Hung Up" by "Madonna" File-format (format): 4.5MB MP3 file encoded at 192Kbps bitrate. Example 2: audio-info (content): A music video called "Hung Up" by "Madonna" file-format (format): 35MB AVI file, MP3 audio codec encoded at 192Kbps, DiVX video codec encoded at 600Kbps