This overview of sound formats generally used in the Internet intends to help you to find your way around. The formats we generally use are WAVE, AIFF, and MP3.

AIFF, AIFF-C
General MIDI (GM)
General Synthesizer (GS)
MIDI
MPEG, MP3
RealAudio, RealVideo
WAVE
XG

The Audio Interchange File Format is a file format for audio files developed by Apple. Aside from the non-compressed audio data it contains the number of channels (mono or stereo), the number of Bits (8 or 16), the sample rate (e.g. 44.1 kHz), and application-specific data parts.

The AIFF format is the Apple standard. AIFF-C is AIFF plus compression. AIFF files on PC are identified by their .aif ending their file names. The operating system supports recording and playback of these formats without requiring any special software. Since standard Internet browsers also support this format, an AIFF file in the Internet can be heard simply by clicking on it.

More information
Technical details: http://www.borg.com/~jglatt/tech/aiff.htm

An extension to the MIDI standard that determines which sounds are assigned to which program numbers; e.g. the GM standard for program number 0 is a piano sound.

An extension to the General-MIDI standard by Roland.

Actually Musical Instruments Digital Interface is not a sound format. Nevertheless, it should be mentioned in this context as the distinction is sometimes not correctly understood. A MIDI file does not contain sound information like a CD; much rather it should be seen as a simple text file that may contain e.g.: "Send program change command 12 to channel 3, hit note C4, duration...".

MIDI is also a succession of commands with the help of which a device is controlled. In many cases this device will be a synthesizer, a keyboard, a sound module, or a sound card, that will produce a sound as a result of this strain of commands. MIDI is also used to remote control other devices, such as effect machines (effect level, various parameters) or amplifiers (volume, channel switching).

Of course in practice this means MIDI files may have the big advantage of being very small (which is especially important in the internet), however, the quality of the reproduced sound depends on the sound producer implemented (sound card). Sound producers of an older make may not even reproduce the correct instrument. The General-MIDI-Standard has remedied this problem, because it determines which sound is connected to which program number.

MPEG is abbreviated for Moving Picture Experts Group, a group that develops different transmission and encryption procedures for audio and video sequences. The standards currently in use are MPEG-1 and MPEG-2. There is no such thing as an MPEG-3-standard. The term MP3 has developed from the data name ending of such files. The correct term would be MPEG Layer 3.

Layer 3 is a part of the MPEG-1 and MPEG-2 standards that compresses audio information. Audio can be compressed either to layer 1, 2 or 3, with the compression and decompression procedures (Codecs) involving different levels of complexity. Layer 3 applies a compression procedure that cleverly takes advantage of the limits of human hearing, filtering out information from the sound source without losing too much quality. In comparison to CD quality (44.1 kHz, 16 bit, stereo), this method achieves a compression rate of up to 1:12, with almost no audible loss of quality.

The great popularity of MP3 files is due to the fact that they have made it possible to download high-quality adio files from the Internet with the bandwidths currently available and within tolerable waiting periods. MP3 is often assoicated with illegal. However, this controversy does not refer to the MP3 format per se or downloading or owning MP3 files. Only some MP3 sites are operated illegally because they offer music (in the MP3 format) without having acquired the according publishing rights.

You need a special player (to palyback) or an encoder (to record) in order to be able to playback or record (code) MP3 files. They are available for download on many Internet pages. Windows98 already includes an MP3 player. MP3 files in the Internet need to be downloaded before they can be played back using a player because current standard browsers do not support the MP3 format.

More information
Official MPEG site: http://drogo.cselt.stet.it/mpeg/
Frauenhofer Institut Integrierte Schaltungen: http://www.iis.fhg.de/amm/techinf/layer3/
Collection of MPEG resources: http://www.mpeg.org/
Commercial MP3 site: http://www.mp3.com/
MP3 software: Tools
Other links in Link Collection

RealAudio and RealVideo are proprietary formats of Real Corporation. They were designed especially for the purpose of audio and video data network transmission. This format supports so-called streaming, i.e. the file is played back as soon as the data becomes to come in (live, so to speak). This is why you do not need to download the entire file before you can play it back as is the case with most other formats. The compression methods applied vary depending on the assigned purpose (voice, music, ...).

You need a special player or encoder in order to be able toplayback RealAudio files. The newer standard browser versions include this player.

More information
Real: http://www.real.com
RealAudio software: Tools
Find more links in our collection of Music Links

The WAVE format was developed by Microsoft and IBM for the Windows platform and is the Windows standard. Aside from the uncompressed audio information, a WAVE file also contains information pertaining to the number of channels (mono or stereo), the sample rate (e.g. 44,1 kHz), and the number of bits (8 or 16). There are several compression codes for the WAVE format, such as Microsoft ADPCM.

Tools for playing back and recording WAVE files are included in all Windows operating systems. You can download and playback WAVE files you find on websites with standard browsers.

More information
Technical details: http://www.borg.com/~jglatt/tech/wave.htm

Yamaha's extension of the General MIDI standard. The XG standard is even more comprehensive than Roland's GS standard.