Fast system and method for computing modulated lapped transforms

A fast computation system stored on computer readable memory of a computer system for computing a spatial transform of an input signal, the fast computation system comprising:

• a window processor having a window function and an operator comprised of a first set of weights, wherein the window processor is preprogrammed for receiving the input signal as sample blocks and the operator is adapted to apply butterfly coefficients determined by the window function to produce resulting vectors, for mapping the input signal to a cascade of butterflies using the first set of weights, and for reordering the cascade of butterflies;
• and
• a transform processor having a transform module for computing a spatial transform from the reordered cascade of butterflies to produce transform coefficients and a coefficient combination operator for combining the transform coefficients to produce an encoded output corresponding to the input signal.

A computer-readable memory device encoded with a set of software instructions for performing a method for computing a spatial transform of an input signal, the set of software instructions having software routines, each routine containing:

• a first parameter value for receiving the input signal as sample blocks and applying butterfly coefficients determined by the first parameter value to the sample blocks to produce resulting vectors, for mapping the input signal with the applied butterfly coefficients to a cascade of butterflies using a first set of weights, and for reordering the cascade of butterflies;
• and
• a second parameter for computing a spatial transform from the reordered cascade of butterflies to produce transform coefficients and for combining the transform coefficients to produce an encoded output corresponding to the input signal.

The method of claim 41, wherein the modulated lapped transform has a sine window.

The method of claim 50, wherein the modulated lapped transform has a sine window.

A fast inverse computation system stored on computer readable memory of a computer system for computing an inverse spatial transform of a preprocessed signal, wherein the preprocessed signal represents an encoded format of an original input signal, the encoded format containing a spatial transform with transform coefficients, the fast inverse computation system comprising:

• an inverse transform processor having a coefficient combination operator for combining the transform coefficients to produce resulting vectors and an inverse transform module for computing an inverse spatial transform from the resulting vectors to produce inverse transform coefficients;
• and
• an inverse window processor having a window function and an operator comprised of a second set of weights, wherein the window processor receives the inverse transform coefficients and is preprogrammed for mapping the inverse transform coefficients to a cascade of butterflies using the second set of weights and reordering the cascade of butterflies and for applying butterfly coefficients determined by a given window function to the mapped inverse transform coefficients to produce a decoded output corresponding to the original input signal.