MP3: Difference between revisions
(→mp3PRO: identifying/locating side data) |
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* Microsoft Audio ID: 0x0055 | * Microsoft Audio ID: 0x0055 | ||
* QuickTime FOURCCs: CBR: ('m', 's', 0x00, 0x55); VBR: '.mp3' | * QuickTime FOURCCs: CBR: ('m', 's', 0x00, 0x55); VBR: '.mp3' | ||
* Patents | * [[MP3 Patents|Patents]] | ||
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. |
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
- See this MPlayer patch: http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2007-March/050609.html
GAIN (MP3Gain) header
There is two versions of this header: one for MP3 and one for AAC.