Adaptive-block-length, adaptive-transforn, and adaptive-window transform coder, decoder, and encoder/decoder for high-quality audio
DCFirst Claim
1. An encoder for the encoding of samples representing a discrete time signal and particularly a music signal, comprisingcontrol means responsive to one or more characteristics of said discrete time signal for adapting at least one of a sample block length, one or more analysis-window functions, and one or more discrete transforms, and for grouping said samples into sample blocks having a length equal to said sample block length, wherein said control means adapts said sample block length for any sample block such that it is different from the length of a previous sample block.analysis-window means responsive to said control means for generating analysis-window weighted blocks by weighting said sample blocks with said one or more analysis-window functions, andtransform means responsive to said analysis-window means and optionally responsive to said control means for generating spectral information by applying said one or more discrete transforms to said analysis-window weighted blocks.
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Abstract
The invention relates in general to high-quality low bit-rate digital transform coding and decoding of information corresponding to audio signals such as music signals. More particularly, the invention relates to signal analysis/synthesis in coding and decoding. The invention can optimize the trade off in transform coders between time resolution and frequency resolution by adaptively selecting the transform block length for each sampled audio segment, and/or can optimize coding gain by adaptively selecting the transform and/or by adaptively selecting the analysis window or the analysis/synthesis window pair.
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Citations
65 Claims
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1. An encoder for the encoding of samples representing a discrete time signal and particularly a music signal, comprising
control means responsive to one or more characteristics of said discrete time signal for adapting at least one of a sample block length, one or more analysis-window functions, and one or more discrete transforms, and for grouping said samples into sample blocks having a length equal to said sample block length, wherein said control means adapts said sample block length for any sample block such that it is different from the length of a previous sample block. analysis-window means responsive to said control means for generating analysis-window weighted blocks by weighting said sample blocks with said one or more analysis-window functions, and transform means responsive to said analysis-window means and optionally responsive to said control means for generating spectral information by applying said one or more discrete transforms to said analysis-window weighted blocks.
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2. An encoder for the encoding of samples representing a discrete time signal and particularly a music signal;
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control means responsive to one or more characteristics of said discrete time signal for adapting a sample block length, for adapting one or more analysis-window functions and/or one or more discrete transforms, and for grouping said samples into sample blocks having a length equal to said sample block length, analysis-window means responsive to said control means for generating analysis-window weighted blocks by weighting said sample blocks with said one or more analysis-window functions, and transform means responsive to said analysis-window means and optionally responsive to said control means for generating spectral information by applying said one or more discrete transforms to said analysis-window weighted blocks.
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27. A decoder for the decoding of a coded signal comprising representations of spectral components of a discrete time signal and particularly a music signal, wherein said decoder comprises
inverse control means responsive to said coded signal for adapting a spectral block length and one or more inverse discrete transforms, and for grouping said representations of spectral components into spectral blocks having a length equal to said spectral block length, and transform means responsive to said inverse control means for generating sample blocks by applying said one or more inverse discrete transforms to said spectral blocks.
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30. A decoder for the decoding of a coded signal comprising representations of spectral components of a discrete time signal and particularly a music signal, wherein said decoder comprises
inverse control means responsive to said coded signal for adapting at least one of a spectral block length, one or more inverse discrete transforms, and one or more synthesis-window functions, and for grouping said representations of spectral components into spectral blocks having a length equal to said spectral block length, wherein said inverse control means adapts said spectral block length for any spectral block such that it is different from the length of a previous spectral block, transform means responsive to said inverse control means for generating sample blocks comprising recovered signal samples by applying said one or more inverse discrete transforms to said spectral blocks, and synthesis-window means responsive to said transform means and optionally responsive to said inverse control means for generating output samples by weighting said sample blocks with said one or more synthesis-window functions.
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37. An encoding method for the encoding of samples representing a discrete time signal and particularly a music signal, comprising
adapting at least one of a sample block length, one or more analysis-window functions, and one or more discrete transforms in response to one or more characteristics of said discrete time signal, and grouping said samples into sample blocks having a length equal to said sample block length, wherein said adapting adapts said sample block length for any sample block such that it is different from the length of a previous sample block, generating analysis-window weighted blocks by weighting said sample blocks with said one or more analysis-window functions, and generating spectral information by applying said one or more discrete transforms to said analysis-window weighted blocks.
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38. An encoding method for the encoding of samples representing a discrete time signal and particularly a music signal, comprising
adapting a sample block length, adapting one or more analysis-window functions and/or one or more discrete transforms in response to one or more characteristics of said discrete time signal, and grouping said samples into sample blocks having a length equal to said sample block length, generating analysis-window weighted blocks by weighting said sample blocks with said one or more analysis-window functions, and generating spectral information by applying said one or more discrete transforms to said analysis-window weighted blocks.
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49. A decoding method for the decoding of a coded signal comprising representations of spectral components of a discrete time signal and particularly a music signal, wherein said decoding method comprises
adapting a spectral block length and one or more inverse discrete transforms in response to said coded signal, and grouping said representations of spectral components into spectral blocks having a length equal to said spectral block length, and generating sample blocks by applying said one or more inverse discrete transforms to said spectral blocks.
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50. A decoding method for the decoding of a coded signal comprising representations of spectral components of a discrete time signal and particularly a music signal, wherein said decoding method comprises
adapting in response to said coded signal at least one of a spectral block length, one or more inverse discrete transforms, and one or more synthesis-window functions in response to said coded signal, and grouping said representations of spectral components into spectral blocks having a length equal to said spectral block length, wherein said adapting adapts said spectral block length for any spectral block such that it is different from the length of a previous spectral block, generating sample blocks comprising recovered signal samples by applying said one or more inverse discrete transforms to said spectral blocks, and generating output samples by weighting said sample blocks with said one or more synthesis-window functions.
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55. An encoder for the encoding of samples representing a discrete time signal and particularly a music signal, comprising
a signal characteristic detector responsive to said discrete time signal, a frame control responsive to said signal characteristic detector comprising at least one of an analysis window function control and a discrete transform control, a buffer responsive to said samples, an analysis window responsive to said buffer and optionally responsive to said frame control, said analysis window comprising one or more analysis-window functions, and a filter bank responsive to said analysis window and optionally responsive to said frame control, said filter bank comprising one or more discrete transforms, wherein at least one of said analysis window and said filter bank is responsive to said frame control.
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60. A decoder for the decoding of a coded signal representing a discrete time signal and particularly a music signal, comprising
a frame control responsive to said coded signal comprising a discrete transform control, and an inverse filter bank responsive to said coded signal and to said frame control, said inverse filter bank comprising one or more inverse discrete transforms.
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61. A decoder for the decoding of a coded signal representing a discrete time signal and particularly a music signal, comprising
a frame control responsive to said coded signal comprising at least one of a discrete transform control and a synthesis window control, an inverse filter bank responsive to said coded signal and optionally responsive to said frame control, said inverse filter bank comprising one or more inverse discrete transforms, and a synthesis window responsive to said inverse filter bank and optionally responsive to said frame control, said synthesis window comprising one or more synthesis-window functions, wherein at least one of said inverse filter bank and said synthesis window is responsive to said frame control.
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64. An encoder for the encoding of samples representing a discrete time signal and particularly a music signal, comprising
control means for grouping said samples into sample blocks having a length equal to a sample block length, analysis-window means for generating analysis-window weighted blocks by weighting said sample blocks with one or more analysis-window functions, and transform means for generating spectral information by applying a discrete transform to said analysis-window weighted blocks, wherein said control means comprises a transform adapting means responsive to one or more characteristics of said discrete time signal for selecting said discrete transform from a plurality of discrete transforms and/or adapting said discrete transform which is a signal-independent transform.
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65. A decoder for the decoding of a coded signal comprising representations of spectral components of a discrete time signal and particularly a music signal, wherein said decoder comprises
inverse control means for grouping said representations of spectral components into spectral blocks having a length equal to a spectral block length, and transform means for generating sample blocks by applying an inverse discrete transform to said spectral blocks, wherein said inverse control means comprises a transform adapting means responsive to said coded signal for selecting said inverse discrete transform from a plurality of inverse discrete transforms and/or adapting said inverse discrete transform which is a signal-independent transform.
Specification