METHODS AND DEVICES FOR PERFORMING A FAST MODIFIED DISCRETE COSINE TRANSFORM OF AN INPUT SEQUENCE

摘要

An improved fast N-point MDCT process and encoder/decoder is disclosed. The N-
point
MDCT may be realized through an N/2-point DCT algorithm. The N/2 DCT transform

matrix is directly factored and the factored DCT transform matrices are used
to develop a
set of equations for realizing the N-point MDCT coefficients from an input
sequence.
The factoring of the DCT transform matrix may include expressing the DCT
transform as
a multiplication of matrices and exploiting mirror images within the matrices.
It may
further include simplifying at least one of the matrices by eliminating a
variable based on
trigonometric identity