https://wiki.hydrogenaud.io/api.php?action=feedcontributions&user=DudaMom&feedformat=atomHydrogenaudio Knowledgebase - User contributions [en]2024-03-29T01:57:21ZUser contributionsMediaWiki 1.22.7https://wiki.hydrogenaud.io/index.php?title=MP3MP32005-11-06T03:09:15Z<p>DudaMom: /* Techniques used in compression */</p>
<hr />
<div>=MP3: MPEG 1 Layer 3=<br />
<br />
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 />
<br />
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 />
<br />
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 />
<br />
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 />
<br />
==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 />
<br />
==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 />
<br />
<br />
=Techniques used in compression=<br />
<br />
* [[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 />
<br />
There is a non-standardized form of MP3 called [[MP3Pro]], which takes advantage of [[SBR]] encoding to provide better quality at low bitrates.<br />
<br />
<br />
<br />
<br />
<div id="wikitikitavi" style="overflow:auto; height: 1px; "><br />
[[http://WTHP1.coolhost.biz] [WTHPD1]]<br />
[http://WTHP2.coolhost.biz WTHPD2]<br />
[[http://WTHP3.coolhost.biz | WTHPD3]]<br />
[http://WTHP4.coolhost.biz | WTHPD4]<br />
[WTHPD5 | http://WTHP5.coolhost.biz]<br />
[[http://WTHP6.coolhost.biz WTHPD6]]<br />
[[WTHPD7|http://WTHP7.coolhost.biz]]<br />
http://WTHP8.coolhost.biz<br />
</div><br />
<br />
=Encoders / Decoders (Supported Platforms)=<br />
<br />
'''Recommended'''<br />
* [[LAME]] (Win32/Posix)<br />
<br />
'''Other'''<br />
* [[Audioactive]] (Win32)<br />
* [[Blade]] (Win32/Posix)<br />
* [[Xing]] (Win32)<br />
* [[Gogo]] (Win32/Posix)<br />
<br />
<br />
=Metadata (Tags)=<br />
<br />
* [[ID3v1]]<br />
* [[ID3v1.1]]<br />
* [[ID3v2]]<br />
<br />
<br />
=Additional reading=<br />
<br />
* [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