Perceptual audio coding with adaptive non-uniform time/frequency tiling using subband merging and the time domain aliasing reduction

An audio processor for processing an audio signal to acquire a subband representation of the audio signal, the audio processor comprising:

• a cascaded lapped critically sampled transform stage configured to perform a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• a time domain aliasing reduction stage configured to perform a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein the cascaded lapped critically sampled transform stage is configured to segment a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein the cascaded lapped critically sampled transform stage is configured to segment a set of bins acauired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform stage of the cascaded lapped critically sampled transform stage, wherein the second lapped critically sampled transform stage is configured to perform lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• wherein the audio processor is configured to form a bitstream from an encoded aliasing reduced subband representation of the audio signal,
• wherein the audio processor is configured to provide the bitstream comprising at least one mergefactor, MF, parameter signaling at least one framelength of the corresponding sets of bins in the bitstream;
• wherein the audio processor is configured to provide the bitstream comprising only a subset of the mergefactor, MF, parameters signaling the framelength of the corresponding sets of bins in the bitstream.

An audio processor for processing an audio signal to acquire a subband representation of the audio signal, the audio processor comprising:

• a cascaded lapped critically sampled transform stage configured to perform a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• a time domain aliasing reduction stage configured to perform a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein the cascaded lapped critically sampled transform stage is configured to segment a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein the cascaded lapped critically sampled transform stage is configured to segment a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform stage of the cascaded lapped critically sampled transform stage, wherein the second lapped critically sampled transform stage is configured to perform lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• wherein the audio processor is configured to form a bitstream from an encoded aliasing reduced subband representation of the audio signal,
• wherein the audio processor is configured to provide the bitstream comprising at least one mergefactor, MF, parameter signaling at least one framelength of the corresponding sets of bins in the bitstream;
• wherein the audio processor is configured to provide the bitstream comprising a time domain aliasing reduction, TDAR, parameter for each corresponding sets of bins.

An audio processor for processing an audio signal to acquire a subband representation of the audio signal, the audio processor comprising:

• a cascaded lapped critically sampled transform stage configured to perform a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• a time domain aliasing reduction stage configured to perform a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein the cascaded lapped critically sampled transform stage is configured to segment a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein the cascaded lapped critically sampled transform stage is configured to segment a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform stage of the cascaded lapped critically sampled transform stage:
• wherein the second lapped critically sampled transform stage is configured to perform lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• wherein the audio processor is configured to form a bitstream from an encoded aliasing reduced subband representation of the audio signal,
• wherein the audio processor is configured to provide the bitstream comprising at least one mergefactor, MF, parameter signaling at least one framelength of the corresponding sets of bins in the bitstream,
• wherein the audio processor is configured to provide the bitstream comprising the at least one mergefactor, MF, parameter such that a time domain aliasing reduction, TDAR, parameter is derivable from the at least one mergefactor, MF, parameter.

An audio processor for processing an audio signal to acquire a subband representation of the audio signal, the audio processor comprising:

• a cascaded lapped critically sampled transform stage configured to perform a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• a time domain aliasing reduction stage configured to perform a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein the cascaded lapped critically sampled transform stage is configured to segment a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein the cascaded lapped critically sampled transform stage is configured to segment a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform stage of the cascaded lapped critically sampled transform stage, wherein the second lapped critically sampled transform stage is configured to perform lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• wherein the audio processor is configured to perform a common/joint optimization for adapting the framelengths using a trellis-grid per set of subband samples.

A method for processing an audio signal to acquire a subband representation of the audio signal, the method comprising:

• performing a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• performing a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform of the cascaded lapped critically sampled transform, wherein the second lapped critically sampled transform comprises performing lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• wherein the weighted combination of the two corresponding sets of subband samples is performed, if the same framelengths are used for two subsequent blocks,
• and/or the weighted combination of the two corresponding sets of subband samples is not performed, if different framelengths are used for two subsequent blocks.

A method for processing an audio signal to acquire a subband representation of the audio signal, the method comprising:

• performing a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• performing a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform of the cascaded lapped critically sampled transform, wherein the second lapped critically sampled transform comprises performing lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• forming a bitstream from an encoded aliasing reduced subband representation of the audio signal,
• providing the bitstream comprising at least one mergefactor, MF, parameter signaling at least one framelength of the corresponding sets of bins in the bitstream;
• wherein providing the bitstream comprises providing the bitstream comprising only a subset of the mergefactor, MF, parameters signaling the framelength of the corresponding sets of bins in the bitstream.

A method for processing an audio signal to acquire a subband representation of the audio signal, the method comprising:

• performing a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• performing a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform of the cascaded lapped critically sampled transform, wherein the second lapped critically sampled transform comprises performing lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• forming a bitstream from an encoded aliasing reduced subband representation of the audio signal,
• providing the bitstream comprising at least one mergefactor, MF, parameter signaling at least one framelength of the corresponding sets of bins in the bitstream;
• wherein providing the bitstream comprises providing the bitstream comprising a time domain aliasing reduction, TDAR, parameter for each corresponding sets of bins.

A method for processing an audio signal to acquire a subband representation of the audio signal, the method comprising:

• performing a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• performing a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform of the cascaded lapped critically sampled transform, wherein the second lapped critically sampled transform comprises performing lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• forming a bitstream from an encoded aliasing reduced subband representation of the audio signal,
• providing the bitstream comprising at least one mergefactor, MF, parameter signaling at least one framelength of the corresponding sets of bins in the bitstream;
• wherein providing the bitstream comprises providing the bitstream comprising the at least one mergefactor, MF, parameter such that a time domain aliasing reduction, TDAR, parameter is derivable from the at least one mergefactor, MF, parameter.

A method for processing an audio signal to acquire a subband representation of the audio signal, the method comprising:

• performing a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• performing a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform of the cascaded lapped critically sampled transform, wherein the second lapped critically sampled transform comprises performing lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• performing a common/joint optimization for adapting the framelengths using a trellis-grid per set of subband samples.

A non-transitory digital storage medium having stored thereon a computer program for performing a method for processing an audio signal to acquire a subband representation of the audio signal, the method comprising:

• performing a cascaded lapped critically sampled transform on at least two partially overlapping blocks of samples of the audio signal, to acquire a set of subband samples on the basis of a first block of samples of the audio signal, and to acquire a corresponding set of subband samples on the basis of a second block of samples of the audio signal;
• and
• performing a weighted combination of two corresponding sets of subband samples, one acquired on the basis of the first block of samples of the audio signal and one acquired on the basis on the second block of samples of the audio signal, to acquire an aliasing reduced subband representation of the audio signal;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the first block of samples using at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the first block of samples;
• wherein performing a cascaded lapped critically sampled transform comprises segmenting a set of bins acquired on the basis of the second block of samples using the at least two window functions, and to acquire at least two sets of bins based on the segmented set of bins corresponding to the second block of samples;
• and
• wherein the sets of bins are processed using a second lapped critically sampled transform of the cascaded lapped critically sampled transform, wherein the second lapped critically sampled transform comprises performing lapped critically sampled transforms comprising the same framelength for at least one set of bins;
• wherein the weighted combination of the two corresponding sets of subband samples is performed, if the same framelengths are used for two subsequent blocks,
• and/or the weighted combination of the two corresponding sets of subband samples is not performed, if different framelengths are used for two subsequent blocks
• when said computer program is run by a computer.