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The 'Music' category is merely a guideline on commercialized uses of a particular format, not a technical assessment of its capabilities. For example, MP3 and AAC dominate the personal audio market in terms of market share, though many other formats are comparably well suited to fill this role from a purely technical standpoint.
The modified discrete cosine transform (MDCT) is a transform based on the type-IV discrete cosine transform (DCT-IV), with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset, where subsequent blocks are overlapped so that the last half of one block coincides with the first half of the next block.
Discrete cosine transform (DCT), developed by Nasir Ahmed, T. Natarajan and K. R. Rao in 1974, [8] provided the basis for the modified discrete cosine transform (MDCT) used by modern audio compression formats such as MP3 [9] and AAC. MDCT was proposed by J. P. Princen, A. W. Johnson and A. B. Bradley in 1987, [10] following earlier work by ...
AAC-LD uses a version of the modified discrete cosine transform (MDCT) audio coding technique called the LD-MDCT. [8] AAC-LD is widely used by Apple as the voice-over-IP (VoIP) speech codec in FaceTime .
The MDCT is used in most modern audio compression formats, such as Dolby Digital (AC-3), [22] [23] MP3 (which uses a hybrid DCT-FFT algorithm), [24] Advanced Audio Coding (AAC), [25] and Vorbis . [26] Nasir Ahmed also developed a lossless DCT algorithm with Giridhar Mandyam and Neeraj Magotra at the University of New Mexico in 1995.
The modified discrete cosine transform (MDCT) is used in the LD-MDCT technique used by the AAC-LD format introduced in 1999. [10] MDCT has since been widely adopted in voice-over-IP (VoIP) applications, such as the G.729.1 wideband audio codec introduced in 2006, [ 11 ] Apple 's FaceTime (using AAC-LD) introduced in 2010, [ 12 ] and the CELT ...
AAC uses only a modified discrete cosine transform (MDCT) algorithm, giving it higher compression efficiency than MP3, which uses a hybrid coding algorithm that is part MDCT and part FFT. [4] AAC is the default or standard audio format for iPhone, iPod, iPad, Nintendo DSi, Nintendo 3DS, Apple Music, [a] iTunes, DivX Plus Web Player, PlayStation ...
The usage profile HE-AAC v1 uses spectral band replication (SBR) to enhance the modified discrete cosine transform (MDCT) compression efficiency in the frequency domain. [3] The usage profile HE-AAC v2 couples SBR with Parametric Stereo (PS) to further enhance the compression efficiency of stereo signals.