IL197976A

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

Abstract

This record has no abstract on file.

IL197976A, drawing sheet 1
Sheet 1 of 40

Term

No projected expiry on record.

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  2. Filed
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18 claims: 7 independent, 11 dependent

  1. 1
    Claims an analysis windower for windowing a frame of timedomain 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 obtain windowed samples, the analysis window function comprising 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 overall energy value of the window coefficients in the first portion is higher than an overall energy value of the window coefficients of the second portion, 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;and a calculator for calculating the audio subband values using the windowed samples, wherein the calculator comprises a time/frequency converter adapted to subband values such that on one frame of generating the audio all subband values based windowed samples represent a spectral representation of the windowed samples of the frame of windowed samples, and wherein the time/frequency converter is adapted to 5 generating complex-valued audio subband values .
  2. 3
    4. Apparatus according to any of the preceding claims, 25 wherein the analysis windower is adapted such that the first portion of window coefficients comprises 1/3 or less than 1/3 of a total number of window coefficients of the sequence of window coefficients and the second portion comprises 2/3 or more than 2/3 of the total 30 number of window coefficients of the sequence of window coefficients.
  3. 4
    5. Apparatus according to any of the preceding claims, wherein the analysis windower is adapted such that a 35 center point of the window coefficients of the analysis window function corresponds to a real value in an index range of the first portion of window coefficients .
  4. 5
    6. Apparatus according to any of the preceding claims, wherein the analysis windower is adapted such that the analysis window function comprises a strictly 5 monotonic decreasing from the window coefficient comprising the highest absolute value of all window coefficients of the analysis window function to a window coefficient of the sequence of window coefficients used for windowing the latest time-domain 10 audio sample. Apparatus according to any of the preceding claims, wherein the analysis windower is adapted such that the window coefficient corresponding to an index n = (T-l) • N comprises an absolute value in the range of 0.9 to 1.1, wherein an index of the sequence of window coefficients is an integer in the range of 0 to N . T - 1, wherein the window coefficient used for windowing the latest time-domain audio input sample of the frame 120 is the window coefficient corresponding to the index N . T - 1, 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 audio input samples of the comprising N time-domain audio latest frame, input time-domain each block samples, and wherein T and N are positive integers and T is larger than 4. Apparatus according to claim 7, wherein the analysis windower is adapted such that the window coefficient corresponding to the index of the window coefficients n = N . T - 1 comprises an absolute value of less than 0.02. Apparatus according to any of the preceding claims, wherein the analysis windower is adapted such that windowing comprises multiplying the timedomain audio input samples x(n) of the frame to obtain 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-l, wherein c(n) is the window coefficient of the analysis window function corresponding to the index n, wherein x(N . T-l) 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.
  5. 7
    11. Apparatus according to any of the preceding claims, 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.
  6. 8
    12. Apparatus for generating real-valued time-domain audio samples, comprising:a calculator for calculating a intermediate time-domain samples from values in audio subband channels, comprising earlier intermediate time-domain samples and later time-domain samples, sequence of audio subband the sequence wherein the calculator comprises a frequency/time converter adapted to generating the sequence of intermediate time-domain samples, such that the audio subband values provided to the calculator represent a spectral representation of the sequence of intermediate time-domain samples, and wherein the frequency/time converter is adapted to generating the sequence of intermediate time/domain samples based on complex-valued audio subband values;a synthesis windower for windowing the sequence of intermediate time-domain samples using a synthesis window function comprising a sequence of window coefficients to obtain windowed intermediate timedomain samples, the synthesis window function comprising 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 overall energy value of the window coefficients in the first portion is higher than an overall energy value of the window coefficients of the second portion, wherein the first group of window coefficients is used for windowing later intermediate time-domain samples and the second group of window coefficients is used for windowing earlier intermediate time-domain samples;and an overlap-adder output stage for processing the windowed intermediate time-domain samples to obtain the time-domain samples.
  7. 10
    14. Apparatus according any of the claims 12 or 13, wherein the synthesis windower is adapted such that the first portion of window coefficients comprises 1/3 or less than 1/3 of the total number of all window coefficients of the sequence of window coefficients and the second portion of window coefficients comprises 2/3 or more than 2/3 of the total number of window coefficients of the sequence of window coefficients .
  8. 11
    15. Apparatus according to any of the claims 12 to 14, wherein the synthesis windower is adapted such that a center point of the window coefficients of the synthesis window function corresponds to a real value in an index range of the first portion of window coefficients . according to any of the claims 12 to the synthesis windower is adapted such synthesis window function comprises monotonic increase from the window of the sequence of window coefficients Apparatus 15, wherein that the a strictly coefficient used for windowing the latest intermediate time-domain sample to the window coefficient comprising the highest absolute value of all window coefficients of the synthesis window function. index n between 0.9 Apparatus according to any of the claims 12 to 16, wherein the window coefficient corresponding to an N comprises an absolute value in the range and 1.1, wherein the index n of the sequence of window coefficients is an integer in the range of 0 to T . N - 1, wherein the window coefficient used for windowing the latest intermediate time-domain sample is the window coefficient corresponding to the index n = 0, wherein T is an integer larger than 4 indicating the number of blocks comprises in the frame of intermediate time-domain apparatus is adapted to time-domain audio samples, the block of time-domain audio samples comprising N time-domain audio samples, wherein N is a positive integer. samples, wherein the generating a block of the the n=0 17, wherein such that to the index
  9. 12
    18. Apparatus according to claim synthesis windower is adapted 25 window coefficient corresponding comprises an absolute value smaller than or equal to 0.02.
  10. 13
    19. Apparatus according to any of the claims 12 to 18, 30 wherein the synthesis windower is adapted such that the window coefficient corresponding to an index n = 3N is smaller than -0.1, wherein the apparatus is adapted to generating a block of time-domain audio samples, the block of time-domain audio samples 35 comprising N time-domain audio samples, wherein N is a positive integer.
  11. 14
    20. Apparatus according to any of the claims 12 to 19, wherein the synthesis windower is adapted such 40 that the windowing comprises multiplying the intermediate time-domain samples g(n) of the sequence of intermediate time-domain samples to obtain the windowed samples z(n) of the windowed frame based on the equation I z(n) = g(n) c(T . N - 1 - n) for n = 0, . . ., Τ . N - 1. 10
  12. 16
    22. Apparatus according to any of the claims 12 to 21, wherein the apparatus is adapted to using the synthesis window function being a time-reverse or index-reversed version of an analysis window function used for generating the audio subband 20 values.
  13. 17
    23. Method for generating complex-valued audio subband values in audio subband channels, comprising:25 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 first group of window coefficients comprising a first portion of the 30 sequence of window coefficients and the 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 overall energy value of the window coefficients in the first portion is higher than an overall energy value of the window coefficients of the second portion, 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, calculating the audio windowed samples, subband values using the wherein calculating converting the audio all subband values samples represent a the windowed samples samples, and comprises time/frequency subband values such that based on one frame of windowed on spectral representation of of the frame of windowed wherein time/frequency converting the values comprises generating the intermediate time/domain samples based on valued audio subband values. audio subband sequence of complex20 Method for generating real-valued time-domain audio samples, comprising: calculating a sequence of intermediate time-domain 25 samples from audio subband values in audio subband channels, the sequence comprising earlier intermediate time-domain samples and later intermediate time-domain samples;wherein calculating comprises frequency/time converting the audio subband values such that the audio subband values represent a spectral representation of the sequence of intermediate timedomain samples;and wherein frequency/time converting comprises generating the sequence of intermediate time/domain samples based on complex-valued audio subband values;windowing the sequence of intermediate time-domain samples using a synthesis window function comprising a sequence of windowed coefficients to obtain windowed intermediate time-domain samples, the synthesis window 5 function comprising a first group of window coefficients comprising a first portion of the sequence of window coefficients and the second group of window coefficients comprising a second portion of the sequence of window coefficients, the first portion 10 comprising less window coefficients than the second portion, wherein an overall energy value of a window coefficient in the first portion is higher than an overall energy value of a window coefficient of the second portion, wherein the first group of window 15 coefficients is used for windowing later intermediate time-domain samples and the second group of window coefficients is used for windowing earlier intermediate time-domain samples;and 20 overlap-adding the windowed time-domain samples to obtain the time-domain samples.