US 5,349,549 A · Forward transform processing apparatus and inverse processing apparatus for modified discrete cosine transforms, and method of performing spectral and temporal analyses including simplified forward and inverse orthogonal transform processing

Abstract

A method for performing a simplified digital spectral analysis on a block of N samples representing an information signal in the time domain, in which the block of N samples is multiplied by a forward transform window to provide a block of N processed samples. The block of processed samples is digitally preprocessed to provide a block of N/4 complex numbers, which is orthogonally transformed, using digital processing equivalent of a Fast Fourier Transform, to provide a block of N/4 transformed complex numbers. The block of transformed complex numbers is then digitally post-processed to provide a block of N/2 spectral coefficients representing the information signal in the frequency domain. In a method of performing a simplified digital temporal analysis on a block of N/2 spectral coefficients representing the information signal in the frequency domain, the block of spectral coefficients is digitally pre-processed to provide a block of N/4 frequency domain complex numbers, which is orthogonally transformed into a block of N/4 time domain complex numbers by digital processing equivalent to a Fast Fourier Transform. The block of N/4 time domain complex numbers is digitally post processed to provide a block of N/2 processed time domain samples, which is re-arrayed and multiplied by an inverse transform window to provide a block of N samples representing the information signal in the time domain.

Claims23

Dependent claims

A forward transform processing apparatus for carrying out a modified discrete cosine transform on a digital input signal, the digital input signal comprising plural samples in the time domain, the apparatus comprising:

(1) means for dividing the digital input signal blocks of N samples, where N is a positive multiple of four;
(2) a multiplier, the multiplier multiplying each block of N samples by a forward transform window to provide a block of N forward transform window processed samples;
and
(3) transform means for transforming the block of N forward transform window processed samples to provide a block of N/2 spectral coefficients, the transform means including:
(a) a preprocessing means for preprocessing the block of N forward transform window processed samples to provide a block of N/4 complex numbers,
(b) an FFT means for performing processing equivalent to a Fast Fourier Transform on the block of N/4 complex numbers to provide a transformed block of N/4 complex numbers;
and
(c) a postprocessing means for post-processing the transformed block of complex numbers to provide the block of N/2 spectral coefficients.

5 more elements

An inverse transform processing apparatus for carrying out a inverse modified discrete cosine transform on spectral coefficients in the frequency domain to provide a digital output signal in the time domain, the apparatus comprising:

(1) means for dividing the spectral coefficients into blocks of N/2 spectral coefficients, where N is a multiple of 4;
(2) inverse transform means for inversely transforming each block of N/2 spectral coefficients to provide a block of N/2 processed samples in the time domain, the inverse transform means including:
(a) a pre-processing means for pre-processing the spectral coefficients in the block of N/2 spectral coefficients to provide a block of N/4 frequency domain complex numbers,
(b) an FFT means for performing processing equivalent to a Fast Fourier Transform on the block of N/4 frequency domain complex numbers to provide a block of N/4 time domain complex numbers, and
(c) a post-processing means for post-processing the block of N/4 time domain complex numbers to provide the block of N/2 processed samples in the time domain;
(3) a means for re-arraying the block of N/2 processed samples in the time domain to provide a block of N samples in the time domain;
(4) a multiplier, the multiplier multiplying the block of N samples in the time domain by an inverse transform window to provide a windowed block of N samples in the time domain;
(5) means for providing successive windowed blocks of N samples in the time domain as the digital output signal.

5 more elements

A method of performing a simplified digital spectral analysis of a block of N samples representing an information signal in the time domain, the spectral analysis providing a block of N/2 spectral coefficients representing the information signal in the frequency domain, the method comprising the steps of:

(1) multiplying the block of N samples representing the information signal in the time domain by a forward transform window to provide a block of N forward transform window processes samples;
(2) digitally preprocessing the block of N forward transform window processed samples to provide a block of N/4 complex numbers;
(3) performing digital processing equivalent to a Fast Fourier Transform on the block of N/4 complex numbers to provide a transformed block of N/4 complex numbers;
and
(4) digitally post-processing the transformed block of complex numbers to provide the block of N/2 spectral coefficients representing the information signal in the frequency domain.

2 more elements

A method of performing a simplified digital temporal analysis of a block of N/2 spectral coefficients representing an information signal in the frequency domain, the temporal analysis providing a block of N samples representing the information signal in the time domain, the method comprising the steps of:

(1) digitally pre-processing the block of N/2 spectral coefficients representing the information signal in the frequency domain to provide a block of N/4 frequency domain complex numbers, where N is a multiple of 4;
(2) performing digital processing equivalent to a Fast Fourier Transform on the block of N/4 frequency domain complex numbers to provide a block of N/4 time domain complex numbers;
(3) digitally post-processing the block of N/4 time domain complex numbers to provide a block of N/2 processed samples in the time domain;
and
(4) digitally re-arraying and multiplying the block of N/2 processed samples in the time domain by an inverse transform window to provide the block of N samples representing the information signal in the time domain.

2 more elements

A medium for storing a compressed digital signal derived from a digital input signal composed of plural samples in the time domain by a method comprising the steps of:

(1) dividing the digital input signal into blocks of N samples, where N is a multiple of four;
(2) multiplying each block of N samples by a forward transform window to provide a block of N forward transform window processed samples;
(3) digitally preprocessing the block of N forward transform window processed samples to provide a block of N/4 complex numbers;
(4) digitally performing processing equivalent to a Fast Fourier Transform on the block of N/4 complex numbers to provide a transformed block of N/4 complex numbers;
(5) digitally post-processing the transformed block of complex numbers to provide a block of N/2 spectral coefficients;
(6) deriving a block of the compressed digital signal from the block of N/2 spectral coefficients;
and
(7) recording successive blocks of the compressed digital signal on the medium.

5 more elements

Dependencies are inferred from the claim text.

Forward transform processing apparatus and inverse processing apparatus for modified discrete cosine transforms, and method of performing spectral and temporal analyses including simplified forward and inverse orthogonal transform processing

Life of this patent

Forward transform processing apparatus and inverse processing apparatus for modified discrete cosine transforms, and method of performing spectral and temporal analyses including simplified forward and inverse orthogonal transform processing

Life of this patent

Abstract

Claims23