https://wiki.hydrogenaudio.org/api.php?action=feedcontributions&feedformat=atom&user=DudaMomHydrogenaudio Knowledgebase - User contributions [en]2026-04-28T20:11:25ZUser contributionsMediaWiki 1.44.2https://wiki.hydrogenaudio.org/index.php?title=MP3&diff=9189MP32005-11-06T03:09:15Z<p>DudaMom: /* Techniques used in compression */</p>
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<div>=MP3: MPEG 1 Layer 3=<br />
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The MP3 algorithm development started in 1987, with a joint cooperation of [http://www.iis.fraunhofer.de/ Fraunhofer IIS-A] and the University of Erlangen. It is standardized as ISO-MPEG Audio Layer-3 (IS 11172-3 and IS 13818-3).<br />
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It soon became the de facto standard for lossy audio encoding, due to the high [[compression rates]] (1/11 of the original size, still retaining considerable quality), the high availability of decoders and the low CPU requirements for playback. (486 DX2-100 is enough for real-time decoding)<br />
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It supports [[multichannel]] files (Although there's no implementation yet), [[sampling rate]]s from 16kHz to 24kHz (MPEG2 Layer 3) and 32kHz to 48kHz (MPEG1 Layer 3)<br />
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Formal and informal listening tests have shown that MP3 at the 160-224 kbps range provide encoded results undistinguishable from the original materials in most of the cases.<br />
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==Pros==<br />
* Widespread acceptance, support in nearly all hardware audio players and devices<br />
* An [[ISO]] standard, part of MPEG specs<br />
* Fast decoding, lower complexity than [[AAC]] or [[Ogg Vorbis|Vorbis]]<br />
* Anyone can create their own implementation (Specs and demo sources available)<br />
* Relaxed licensing schedule<br />
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==Cons==<br />
* Lower performance / efficiency than modern codecs.<br />
* Problem cases that trip out all transform codecs.<br />
* Sometimes, maximum bitrate (320kbps) isn't enough.<br />
* No multichannel implementations.<br />
* Unusable for high definition audio (sampling rates higher than 48kHz).<br />
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=Techniques used in compression=<br />
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* [[Huffman coding]]<br />
* [[Quantization]]<br />
* [[Joint stereo|M/S matrixing]]<br />
* [[Intensity stereo]]<br />
* Channel coupling<br />
* Modified discrete cosine transform ([[MDCT]])<br />
* Polyphase filter bank<br />
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There is a non-standardized form of MP3 called [[MP3Pro]], which takes advantage of [[SBR]] encoding to provide better quality at low bitrates.<br />
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=Encoders / Decoders (Supported Platforms)=<br />
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'''Recommended'''<br />
* [[LAME]] (Win32/Posix)<br />
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'''Other'''<br />
* [[Audioactive]] (Win32)<br />
* [[Blade]] (Win32/Posix)<br />
* [[Xing]] (Win32)<br />
* [[Gogo]] (Win32/Posix)<br />
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=Metadata (Tags)=<br />
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* [[ID3v1]]<br />
* [[ID3v1.1]]<br />
* [[ID3v2]]<br />
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=Additional reading=<br />
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* [http://www.audiocoding.com/modules/wiki/?page=MP3 MP3 at Audiocoding Wiki]<br />
* [[MPEG1 Layer 3]] - Technical explanation of MP3 encoding.<br />
* [http://www.rjamorim.com/test/mp3-128/results.html Roberto's listening test] featuring MP3 encoders<br />
* [http://uncyclopedia.org/wiki/MP3 MP3 definition at Uncyclopedia]</div>DudaMom