Apparatus and method for generating audio subband values and apparatus and method for generating time-domain audio samples

Patent metadata

Field	Value
Publication number	US-RE50132-E
Application number	US-200717845465-A
Country	US
Kind code	E1
Filing date	Oct 23, 2007
Priority date	Oct 25, 2006
Publication date	Sep 17, 2024
Grant date	Sep 17, 2024

Abstract

An embodiment of an apparatus for generating audio subband values in audio subband channels includes an analysis windower for windowing a frame of time-domain audio input samples being in a time sequence extending from an early sample to a later sample using an analysis window function including a sequence of window coefficients to obtain windowed samples. The analysis window function includes a first number of window coefficients derived from a larger window function including a sequence of a larger second number of window coefficients, wherein the window coefficients of the window function are derived by an interpolation of window coefficients of the larger window function. The apparatus further includes a calculator for calculating the audio subband values using the windowed samples.

First claim

The invention claimed is:

1. An apparatus for generating audio subband values in audio subband channels, comprising:
an analysis windower for windowing a frame of time−domain audio input samples being in a time sequence extending from an early sample to a later sample using an analysis window function comprising a sequence of window coefficients to acquire windowed samples, the analysis window function comprising a first number of window coefficients derived from a larger window function comprising a sequence of a larger second number of window coefficients, wherein the window coefficients of the window function are derived by an interpolation of window coefficients of the larger window function; and wherein the second number is an even number; and a calculator for calculating the audio subband values using the windowed samples.

2. The apparatus according to claim 1 , wherein the apparatus is adapted to interpolating the window coefficients of the larger window function to acquire the window coefficients of the window function.

3. The apparatus according to claim 1 , wherein the apparatus or the analysis windower is adapted such that the window coefficients of the window function are linearly interpolated.

4. The apparatus according to claim 1 , wherein the apparatus or the analysis windower is adapted such that the window coefficients of the analysis window function are interpolated based on two consecutive window coefficients of the larger window function according to the sequence of the window coefficients of the larger window function to acquire one window coefficient of the window function.

5. The apparatus according to claim 1 , wherein the apparatus or the analysis windower is adapted to acquire the window coefficients c(n) of the analysis window function based on the equation
c(n)=½(c 2 (2n)+c 2 (2n+1)),

wherein n is an integer indicating an index of the window coefficients c(n), and c 2 (n) is a window coefficient of the larger window function.

6. The apparatus according to claim 5 , wherein the apparatus or the analysis windower is adapted such that the window coefficients c 2 (n) of the larger window function obey the relations given in the table in Annex 4.

7. The apparatus according to claim 1 , wherein the analysis windower is adapted such that windowing comprises multiplying the time−domain audio input samples x(n) of the frame to acquire the windowed samples z(n) of the windowed frame based on the equation
z(n)=x(n)·c(n)

wherein n is an integer indicating an index of the sequence of window coefficients in the range of 0 to T·N−1, wherein c(n) is the window coefficient of the analysis window function corresponding to the index n, wherein x(N·T−1) is the latest time−domain audio input sample of a frame of time−domain audio input samples, wherein the analysis windower is adapted such that the frame of time−domain audio input samples comprises a sequence of T blocks of time−domain audio input samples extending from the earliest to the latest time−domain audio input samples of the frame, each block comprising N time−domain audio input samples, and wherein T and N are positive integers and T is larger than 4.

8. The apparatus according to claim 1 , wherein the analysis windower is adapted such that the analysis window function comprises a first group of window coefficients comprising a first portion of the sequence of window coefficients and a second group of window coefficients comprising a second portion of the sequence of window coefficients, wherein the first portion comprises less window coefficients than the second portion, wherein an energy value of the window coefficients in the first portion is higher than an energy value of the window coefficients of the second portion, and wherein the first group of window coefficients is used for windowing later time−domain samples and the second group of window coefficients is used for windowing earlier time−domain samples.

9. The apparatus according to claim 1 , wherein the apparatus is adapted to using an analysis window function being a time−reversed or index-reversed version of a synthesis window function to be used for the audio subband values.

10. The apparatus according to claim 1 , wherein the analysis windower is adapted such that the larger window function is asymmetric with respect to the sequence of window coefficients.

11. An apparatus for generating time−domain audio samples, comprising:
a calculator for calculating a sequence of intermediate time−domain samples from audio subband values in audio subband channels, the sequence comprising earlier intermediate time−domain samples and later time−domain samples;
a synthesis windower for windowing the sequence of intermediate time−domain samples using a synthesis window function comprising a sequence of window coefficients to acquire windowed intermediate time−domain samples, the synthesis window function comprising a first number of window coefficients derived from a larger window function comprising a sequence of a larger second number of window coefficients,
wherein the window coefficients of the window function are derived by an interpolation of window coefficients of the larger window function; and
wherein the second number is even; and
an overlap-adder output stage for processing the windowed intermediate time−domain samples to acquire the time−domain samples.

12. The apparatus according to claim 11 , wherein the apparatus is adapted to interpolating the window coefficients of the larger window function to acquire the window coefficients of the window function.

13. The apparatus according to claim 11 , wherein the apparatus is adapted such that the window coefficients of the synthesis window function are linearly interpolated.

14. The apparatus according to claim 11 , wherein the apparatus is adapted such that the window coefficients of the synthesis window function are interpolated based on two consecutive window coefficients of the larger window function according to the sequence of window coefficients of the larger window function to acquire one window coefficient of the window function.

15. The apparatus according to claim 11 , wherein the apparatus is adapted to acquire the window coefficients c(n) of the synthesis window function based on equation
c(n)=½(c 2 (2n)+c 2 (2n+1)),

wherein c 2 (n) are window coefficients of a larger window function corresponding to the index n.

16. The apparatus according to claim 15 , wherein the apparatus is adapted such that the window coefficient c 2 (n) fulfill the relations given in the table in Annex 4.

17. The apparatus according to claim 11 , wherein the synthesis window is adapted such that the windowing comprises multiplying the intermediate time−domain samples g(n) of the sequence of intermediate time−domain samples to acquire the windowed samples z(n) of the windowed frame based on the equation
z(n)=g(n)·c(T−N−1−n)

for n=0, . . . , T·N−1.

18. The apparatus according to claim 11 , wherein the synthesis windower is adapted such that the synthesis window function comprises a first group of window coefficients comprising a first portion of the sequence of window coefficients and a second group of window coefficients comprising a second portion of the sequence of window coefficients, the first portion comprising less window coefficients than the second portion, wherein an energy value of the window coefficients in the first portion is higher than an energy value of the window coefficients of the second portion, and wherein the first group of window

Assignees

• Fraunhofer Ges Forschung

Inventors

• Schnell Markus
• Lutzky Manfred
• Lohwasser Markus
• Schmidt Markus
• Gayer Marc
• Mellar Michael
• Edler Bernd
• Multrus Markus
• Schuller Gerald
• Geiger Ralf
• Grill Bernhard

Classifications

• G10L21/038

  using band spreading techniques · CPC title

• G10L25/45

  characterised by the type of analysis window · CPC title

• H03H17/0266

  Filter banks · CPC title

• G10L19/022 Primary

  Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring · CPC title

• G10L19/02 Primary

  using spectral analysis, e.g. transform vocoders or subband vocoders · CPC title