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Entries found for search: MPEG

MPEG/MPEG-1 : Moving Picture Expert Group. A body that defined a standard for data compression specifically for moving images: animation, audio, and video. This compression scheme includes its own file format. It is a type of delta modulation (differential) compression and hence very efficient, but not useful for nonlinear editing applications. Compression ratios are up to 200:1, lossy but acceptable. There are three layers of MPEG1 encoding of increasing complexity, each layer with its own format. Layer I is fast with typically a 4:1 reduction in data rate with a 32-band filter bank, but offers less compression for comparable quality. Layer II (.MP2 files) is a popular compromise for use with audio files with ratios of 5:1 to 12:1, retaining much of the original sound fileís quality by employing more complex spectral analysis. At a ratio of 8:1, CD-rate audio exhibits little audible loss. Layer III takes longer to compress, but offers higher ratios while retaining much of the audio quality by varying filter bank bandwidths to better simulate the critical bands in human hearing as well as some nonlinear quantizing to increase the efficiency of the data reduction. See MPEG-2, MPEG-3, MPEG-4, DLS-2."

MPEG-2 : A professional standard for MPEG requiring specialized hardware and software; not used in consumer systems. MPEG-2 is an extension of MPEG-1 providing multichannel surround-sound capabilities such as 5.1, although other mixes are also supported. The original MPEG-2 was designed to be backward compatible with MPEG-1, although an incompatible MPEG-2 NBC standard has gained approval for DVDs and broadcast applications.

MPEG-3 : A later MPEG standard which uses a compression ratio of approximately 13:1. The format is fast enough and good enough that this format is widely used to send digital music over data lines (the internet), and is supported by Mac, PC, and UNIX platforms. In addition, the MPEG-3 compressed file format is compatible with all computers.

MPEG-4 : Heavily influenced by Apple computerís QuickTime™, MPEG-4 is aimed primarily at game applications. In addition to streaming video and digital audio, it allows for the transmission of MIDI, provides a GM-compatible synthesizer, facilitates the transfer and playback of DLS-2 and MIDI files, and incorporates a user-configurable synthesis language. This latter feature is called the Structured Audio Orchestra (SAOL) allowing the user to specify almost any existing synthesis method and create algorithms at one end, and have the sound played back identically at the end-userís player. The MPEG-4 specification includes: DLS-2, MIDI/DLS sync, SAOL, digital audio transmission, audio spatialization, and text-to-speech.



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