MIDI (Musical Instrument Digital Interface)
MIDI (Musical Instrument Digital Interface) is a protocol designed for recording and playing back music on digital synthesizers that is supported by many makes of personal computer sound cards. Originally intended to control one keyboard from another, it was quickly adopted for the personal computer. Rather than representing musical sound directly, it transmits information about how music is produced. The command set includes note-ons, note-offs, key velocity, pitch bend and other methods of controlling a synthesizer. The sound waves produced are those already stored in a wavetable in the receiving instrument or sound card.
Since a MIDI file only represents player information, it is far more concise than formats that the sound directly. An advantage is very small file size. A disadvantage is the lack of specific sound control.
With a program that provides this interface, you can create music using a standard keyboard or other input device. You or others can then play your MIDI-conforming creation with the same or another program and a sound card as a music synthesizer. The MIDI program may come with a graphical user interface that looks like a sound studio control room. Many sound cards come as a package with MIDI software (for example, Media Vision's Pro Audio Studio 16).
The MIDI protocol uses eight-bit serial transmission with one start bit and one stop bit, has a 31.25 Kbs data rate, and is asynchronous. Connection is made through a five-pin DIN plug, of which three pins are used.
MP3 (MPEG-1 Audio Layer-3)
MP3 (MPEG-1 Audio Layer-3) is a standard technology and format for compressing a sound sequence into a very small file (about one-twelfth the size of the original file) while preserving the original level of sound quality when it is played. MP3 files (identified with the file name suffix of ".mp3") are available for downloading from a number of Web sites. Many Windows 98 users will find that they have a player built into their operating system. Otherwise, you can download a player from one of several popular MP3 sites. MP3 files are usually download-and-play files rather than streaming sound files that you link-and-listen-to with RealPlayer and similar products (However, streaming MP3 is possible.) Winamp (PC), MacAmp (Mac), and mpeg123 (UNIX) are popular MP3 players, but there are many others. To create an MP3 file, you use a program called a ripper to get a selection from a CD onto your hard drive and another program called an encoder to convert the selection to an MP3 file. Most people, however, simply download MP3s from someone else and play them.
Digital audio is typically created by taking 16 bit samples a second of the analog signal. Since this signal is typically spread out over a spectrum of 44.1 thousand cycles per second (kHz), this means that one second of CD quality sound requires 1.4 million bits of data. Using their knowledge of how people actually perceive sound, the developers of MP3 devised a compression algorithm that reduces data about sound that most listeners can not perceive. MP3 is currently the most powerful algorithm in a series of audio encoding standards developed under the sponsorship of the Motion Picture Experts Group (MPEG) and formalized by the International Organization for Standardization (ISO).
Since it is relatively easy to create MP3 files from CD selections and make them available on Web sites for downloading, companies and sites that promote the MP3 format are sometimes accused of encouraging copyright violations. (It is illegal to copy music from a CD and redistribute it unless you have the copyright owner's permission.) On the other hand, MP3 enthusiasts claim that what CD publishers are afraid of is any kind of non-CD distribution. While there are several proposals for how to discourage such piracy, there is currently no secure distribution and copyright management standard that publishers and other parties agree upon.
Several Web sites are promoting MP3 as both a high-quality audio format and as a way in which self-publishers can gain ready access to an audience. Currently, some music publishers are providing sample cuts in the MP3 format as a way to entice users to buy a CD. However, not much mainstream copyrighted material is available except as an illegal download.
As an alternative approach to individual MP3 downloads, IBM and five recording companies plan to offer entire CD downloads to users with access to high-bandwidth cable modem service. Formerly called Madison, the service, which will be tested during 1999, will ensure royalty payment to the artists and publishers. The Recording Industry Association of America (RIAA) is also working on a Secure Digital Music Initiative (SDMI).
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