Difference between revisions of "MP3"

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(link to the MP3 patents page)
 
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* Patents: US5214678, US5323396, US5777992
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* Company: Fraunhofer
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* Microsoft Audio ID: 0x0055
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* QuickTime FOURCCs: CBR: ('m', 's', 0x00, 0x55); VBR: '.mp3'
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* [[MP3 Patents|Patents]]
  
Lossy audio coding using a time-frequency transform consisting of a 32-subband QM filter followed by an 18-point MDCT on blocks of 576 samples.  In addition, coded frames may be padded by 1 bit as necessary to maintain a strict CBR.  This rather odd design was meant to provide backwards compatibility with the blocksize and bit rates of the existing MP2 format.  Although it is less efficient than using a pure MDCT (eg AAC and Ogg Vorbis) MP3 has become a de facto standard since it was the first widely available format.
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Lossy audio coding using a time-frequency transform consisting of a 32-subband polyphase quadrature filter followed by an 18-point [[Discrete Cosine Transform|MDCT]] on blocks of 576 samples.  Each coded frame is padded to a byte boundary.  In addition, coded frames may be padded by 1 byte as necessary to maintain a strict CBR.  This rather odd design was meant to provide backwards compatibility with the blocksize and bit rates of the existing [[MP2]] format.  Although it is less efficient than using a pure MDCT (e.g. [[AAC]] and [[Vorbis]]) MP3 has become a de facto standard since it was the first widely available format.
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== Extensions ==
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=== mp3PRO ===
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mp3PRO is MP3 + [[Spectral Band Replication|SBR (Spectral Band Replication)]]. (Standard MP3 decoders can decode mp3PRO encoded files/streams but without SBR you do not get the full quality. A SBR decoder could be share code with an [[AAC#HE-AAC|HE-AAC]] (aacPlus) decoder as HE-AAC also uses SBR).
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A [http://www.google.com/patents?id=XLmWAAAAEBAJ US Patent application] explains how to identify and locate the SBR data.
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=== mp3HD ===
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mp3HD is MP3-based lossless audio codec. This codec has backward compatibility to MP3 and extensions are in ID3 tag.
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=== XING and VBRI headers ===
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* See this MPlayer patch: http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2007-March/050609.html
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=== GAIN ([http://mp3gain.sourceforge.net MP3Gain]) header ===
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There is two versions of this header: one for MP3 and one for [[AAC]].
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[[Category:Audio Codecs]]

Latest revision as of 23:50, 30 May 2010

  • Company: Fraunhofer
  • Microsoft Audio ID: 0x0055
  • QuickTime FOURCCs: CBR: ('m', 's', 0x00, 0x55); VBR: '.mp3'
  • Patents

Lossy audio coding using a time-frequency transform consisting of a 32-subband polyphase quadrature filter followed by an 18-point MDCT on blocks of 576 samples. Each coded frame is padded to a byte boundary. In addition, coded frames may be padded by 1 byte as necessary to maintain a strict CBR. This rather odd design was meant to provide backwards compatibility with the blocksize and bit rates of the existing MP2 format. Although it is less efficient than using a pure MDCT (e.g. AAC and Vorbis) MP3 has become a de facto standard since it was the first widely available format.


Extensions

mp3PRO

mp3PRO is MP3 + SBR (Spectral Band Replication). (Standard MP3 decoders can decode mp3PRO encoded files/streams but without SBR you do not get the full quality. A SBR decoder could be share code with an HE-AAC (aacPlus) decoder as HE-AAC also uses SBR).

A US Patent application explains how to identify and locate the SBR data.

mp3HD

mp3HD is MP3-based lossless audio codec. This codec has backward compatibility to MP3 and extensions are in ID3 tag.

XING and VBRI headers

GAIN (MP3Gain) header

There is two versions of this header: one for MP3 and one for AAC.