Encoding and decoding using specially designed pairs of analysis and synthesis windows
DCFirst Claim
1. A method for encoding a signal comprising signal samples, said method comprisinggenerating a window-weighted sample block by weighting a block of said signal samples with a window function, wherein said window function is an analysis window within an analysis-/synthesis window pair, each of length N, and the product of both windows in said pair is a product window of length N with an overlap interval V, said product window when overlapped with a shifted replica of itself sums to a constant value across the overlap interval,filtering said window-weighted sample block to generate frequency subband information, andrepresenting said frequency subband information in a form suitable for transmission or storage,wherein said analysis-/synthesis-window pair is prederived by(1) generating an initial window having a length of 1+V,(2) generating an interim window by convolving said initial window with a unit pulse function of length N-V,(3) defining a scaling factor by convolving said initial window with a unit pulse function of length one,(4) obtaining said product window by dividing said interim window by said scaling factor, and(5) obtaining said window function by taking the Ath power of said product window, wherein 0<
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Abstract
The invention relates to the design of analysis and synthesis windows for use in high-quality transform encoding and decoding of audio signals, especially encoding and decoding having a short signal-propagation delay. The design method derives a pair of analysis/synthesis windows from a known window function which satisfy various filter selectivity and window overlap-add constraints.
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Citations
20 Claims
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1. A method for encoding a signal comprising signal samples, said method comprising
generating a window-weighted sample block by weighting a block of said signal samples with a window function, wherein said window function is an analysis window within an analysis-/synthesis window pair, each of length N, and the product of both windows in said pair is a product window of length N with an overlap interval V, said product window when overlapped with a shifted replica of itself sums to a constant value across the overlap interval, filtering said window-weighted sample block to generate frequency subband information, and representing said frequency subband information in a form suitable for transmission or storage, wherein said analysis-/synthesis-window pair is prederived by (1) generating an initial window having a length of 1+V, (2) generating an interim window by convolving said initial window with a unit pulse function of length N-V, (3) defining a scaling factor by convolving said initial window with a unit pulse function of length one, (4) obtaining said product window by dividing said interim window by said scaling factor, and (5) obtaining said window function by taking the Ath power of said product window, wherein 0<
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3. A method for reproducing a signal represented by encoded information, said method comprising
receiving said encoded information and extracting frequency subband information therefrom, filtering said frequency subband information to generate a signal sample block, and weighting said signal sample block with a window function, wherein said window function is a synthesis window within an analysis-/synthesis-window pair, each of length N, and the product of both windows in said pair is a product window of length N with an overlap interval V, said product window when overlapped with a shifted replica of itself sums to a constant value across the overlap interval, wherein said analysis-/synthesis-window pair is prederived by (1) generating an initial window having a length of 1+V, (2) generating an interim window by convolving said initial window with a unit pulse function of length N-V, (3) defining a scaling factor by convolving said initial window with a unit pulse function of length one, (4) obtaining said product window by dividing said interim window by said scaling factor, and (5) obtaining said window function by taking the Sth power of said product window, wherein 0<
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10. An apparatus for encoding a signal comprising signal samples, said encoder comprising
means for obtaining a window function, wherein said window function is an analysis window within an analysis-/synthesis-window pair, each of length N, and the product of both windows in said pair is a product window of length N with an overlap interval V, said product window when overlapped with a shifted replica of itself sums to a constant value across the overlap interval, said window function obtained by (1) generating an initial window having a length of 1+V, (2) generating an interim window by convolving said initial window with a unit pulse function of length N-V, (3) defining a scaling factor by convolving said initial window with a unit pulse function of length one, (4) obtaining said product window by dividing said interim window by said scaling factor, and (5) obtaining said window function by taking the Ath power of said product window, wherein 0< - A<
1,means for generating a window-weighted sample block by weighting a block of said signal samples with said window function, subband means for generating frequency subband information in response to said window-weighted sample block, and means for representing said frequency subband information in a form suitable for transmission or storage. - View Dependent Claims (11, 14, 15, 16, 17, 18)
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12. An apparatus for reproducing a signal represented by encoded information, and decoder comprising
means for obtaining a window function, wherein said window function is a synthesis window within an analysis-/synthesis-window pair, each of length N, and the product of both windows in said pair is a product window of length N with an overlap interval V, said product window when overlapped with a shifted replica of itself sums to a constant value across the overlap interval, said window function obtained by (1) generating an initial window having a length of 1+V, (2) generating an interim window by convolving said initial window with a unit pulse function of length N-V, (3) defining a scaling factor by convolving said initial window with a unit pulse function of length one, (4) obtaining said product window by dividing said interim window by said scaling factor, and (5) obtaining said window function by taking the Sth power of said product window, wherein 0< - S<
1,means for receiving said encoded information and extracting frequency subband information therefrom, subband means for generating a signal sample block in response to said frequency subband information, and means for weighing said signal sample block with said window function. - View Dependent Claims (13)
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19. An apparatus for encoding a signal comprising signal samples, said encoder comprising
means for generating a window-weighted sample block by weighting a block of said signal samples with a window function, wherein said window function is an analysis window within an analysis-/synthesis-window pair, each of length N, and the product of both windows in said pair is a product window of length N with an overlap interval V, said product window when overlapped with a shifted replica of itself sums to a constant value across the overlap interval, wherein said analysis-/synthesis-window pair is prederived by (1) generating an initial window having a length of 1+V, (2) generating an interim window by convolving said initial window with a unit pulse function of length N-V, (3) defining a scaling factor by convolving said initial window with a unit pulse function of length one, (4) obtaining said product window by dividing said interim window by said scaling factor, and (5) obtaining said window function by taking the Ath power of said product window, wherein 0< - A<
1,a filter bank generating subband signals in response to said window-weighted sample block, and means for representing said subband signals in a form suitable for transmission or storage.
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20. An apparatus for reproducing a signal represented by encoded information, said decoder comprising
means for receiving said encoded information and extracting frequency subband information therefrom, an inverse filter bank generating a signal block in response to said frequency subband information, and means for weighting said signal sample block with a window function, wherein said window function is a synthesis window within an analysis-/synthesis-window pair, each of length N, and the product of both windows in said pair is a product window of length N with an overlap interval V, said product window when overlapped with a shifted replica of itself sums to a constant value across the overlap interval, wherein said analysis-/synthesis-window pair is prederived by (1) generating an initial window having a length of 1+V, (2) generating an interim window by convolving said initial window with a unit pulse function of length N-V, (3) defining a scaling factor by convolving said initial window with a unit pulse function of length one, (4) obtaining said product window by dividing said interim window by said scaling factor, and (5) obtaining said window function by taking the Sth power of said product window, wherein 0< - S<
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Specification