There is a set of standards for video labelled MPEG. Some apply to video; others apply to audio. This note will cover only the basic features; for details see the usual sites as linked under URLs. Like all lossy compression schemes, the quality of the output of MPEG encoding is less than that of the original video or audio source. In general, the user has enough control to select a balance in compression between loss of quality and reduction of file size, but one should not hope for miracles. Experimentation is needed to determine what looks and sounds right for you.
MPEG video was to be available in three flavors. MPEG 1 can be produced and played back (encoded and decoded) in software alone and on a fast system can provide reasonable quality at 352x240 pixels or about half of the usual minimum screen size. MPEG 2 is more efficient, supports higher resolution and requires specialized (and costly) hardware to encode and moderately priced hardware to decode; it is currently used for DVD playback. MPEG 3 is still higher quality and was intended for high-definition television (HDTV), but it has been suspended until requirements can be fully defined.
MPEG 1 is readily produced on a PC and is suitable for recording from and to VHS videotape. 'Readily' must be taken with a large grain of salt, however, since software encoding takes many times real-time. The MPEG codec is quite efficient in storage requirements and provides a high-quality picture at reasonable file sizes by video standards. A properly encoded MPEG 1 file can be turned into VCD (Video CD) with Easy CD Creator and played on a suitable set-top player. More useful for many is that it can be played on a personal computer and even accessed by a WWW browser with a suitable helper application. Many other codecs (coder/decoder) are available for video; their products are usually in the form of avi or mov files depending on whether they are packaged in Windows AVI or Mac/Windows QuickTime envelopes.
MPEG Layer 1 is a moderately compressed audio format which is used in some video to reduce decompression load. Layer 2 is usefully compressed and can be generated easily in software encoders. The usual extension for MPEG Layer 2 is .mp2. Layer 3 is still more highly compressed; the shareware program l3enc (with its companion l3dec) appears to be the most popular choice for that process. Other mp3 encoders are available or on their way.
MP2 and MP3 playback require an appropriate application; usually both are provided in a single program. One with several advantages is the inexpensive shareware WinAmp (and the companion MacAmp) from Nullsoft (http://www.nullsoft.com/ ) It offers a great deal of flexibility so that good results can be obtained on a slower computer; a graphic equalizer with some compression of dynamic range; and even the ability to export an MPEG file in decompressed form in the wav format. Since CD-DA is uncompressed, an MPEG file cannot be the starting point for recording an audio CD-R. An MPEG can be stored on a disc, but to make it useful in a CD player, it must be decompressed to wav before burning.
Streaming video and audio refers to the ability to play the picture and sound as it is being received. In general, that requires special capability on the server side and is not available from a CD-R. The formats used for streaming include RealAudio, RealVideo and TrueVoice. The RealMedia capabilities are very inexpensive, but require that the user either download or buy the player program. Efficiency and quality for video are less than MPEG, but more than some video codecs; RealAudio options are quite attractive, but no converter is available to produce wav files from ra. In addition, the author of a RealMedia file may mark it so that from a streaming server it cannot be saved to disc by the user.
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