Difference between revisions of "MP3"

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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.
 
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 + [http://www.codingtechnologies.com/products/sbr.htm SBR (Spectral Band Replication)]. (Standard MP3 decoders can decode mp3PRO encoded files/streams but without [http://www.codingtechnologies.com/products/sbr.htm SBR] you do not get the full quality. A [http://www.codingtechnologies.com/products/sbr.htm SBR] decoder could be share code with a aacPlus decoder as aacPlus also uses [http://www.codingtechnologies.com/products/sbr.htm SBR]).
  
 
[[Category:Audio Codecs]]
 
[[Category:Audio Codecs]]

Revision as of 04:05, 6 October 2007

  • Microsoft Audio ID: 0x0055
  • QuickTime FOURCCs: CBR: ('m', 's', 0x00, 0x55); VBR: '.mp3'
  • Patents: US5214678, US5323396, US5777992

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 a aacPlus decoder as aacPlus also uses SBR).