ABSTRACT
The modified discrete cosine transform (MDCT) is a lapped transform and a type of linear discrete block transformation where the basic functions of the transformation overlap the block boundaries. The MDCT is compared to other Fourier-related transforms in that it has half as many outputs as inputs. The MDCT is equivalent to a Shifted discrete Fourier transform. The Properties of the MDCT is not an orthogonal transform. The MDCT becomes an orthogonal transform if the signal length is infinite. The MDCT is employed in most modern lossy audio formats such as MP3, Vorbis, Windows Media Audio, Cook and Advanced audio coding which are different lossy audio compression codecs. The MDCT spectrum of a signal is the Fourier spectrum of the signal mixed with its alias. This compromises the performance of MDCT as a Fourier spectrum analyzer and leads to possible mismatch problems between MDCT- and discrete Fourier transform -based perceptual models.
