Discrete Cosine Transform
From Hydrogenaudio Knowledgebase
The DCT is similar to the discrete fourier transform: It transforms a signal from the time domain to the frequency domain. Just as the fourier transform uses sine and cosine waves to represent a signal, the DCT only uses cosine waves. While DCT is mostly used in image compression, MDCT (modified DCT) is used in audio encoding. The DCT is an invertible, discrete orthogonal transformation.
