Analysis filterbank, synthesis filterbank, encoder, de-coder, mixer and conferencing system

Synthesis filterbank for filtering a plurality of input frames of an audio signal, each input frame comprising a number of ordered input values, comprising:

• a frequency/time converter configured to provide a plurality of output frames, an output frame comprising a number of ordered output samples, an output frame being a time representation of an input frame;
• a windower configured to generate a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples;
• and
• wherein the windower is configured to provide the plurality of windowed samples for a processing in an overlapping manner based on a sample advance value;
• an overlap/adder configured to provide an added frame comprising a start section and a remainder section, an added frame comprising a plurality of added samples by adding at least three windowed samples from at least three windowed frames for an added sample in the remainder section of an added frame and by adding at least two windowed samples from at least two different windowed frames for an added sample in the start section,
• wherein the number of windowed samples added to obtain an added sample in the remainder section is at least one sample higher compared to the number of windowed samples added to obtain an added sample in the start section, or
• wherein the windower is configured to disregard at least the earliest output value according to the order of the ordered output samples or to setting the corresponding windowed samples to a predetermined value or to at least a value in a predetermined range for each windowed frame of the plurality of windowed frames;
• and
• wherein the overlap/adder is configured to provide the added sample in the remainder section of an added frame based on at least three windowed samples from at least three different windowed frames and an added sample in the start section based on at least two windowed samples from at least two different windowed frames, wherein the frequency/time converter, the windower, or the overlap/adder comprises a hardware implementation.

Synthesis filterbank for filtering a plurality of input frames of an audio signal, each input frame comprising M ordered input values yk(0), . . . , yk(M−1), wherein M is a positive integer, and wherein k is an integer indicating a frame index,

• comprising:
• an inverse type-IV discrete cosine transform frequency/time converter configured to provide a plurality of output frames, an output frame comprising 2M ordered output samples xk(0), . . . , xk(2M−1) based on the input values yk(0), . . . , yk(M−1);
• a windower configured to generate a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples zk(0), . . . , zk(2M−1) based on the equation
• zk(n)=w(n)·xk(n)
• for n=0, . . . , 2M−1,
• wherein n is an integer indicating a sample index, and wherein w(n) is a real-valued window function coefficient corresponding to the sample index n;
• an overlap/adder configured to provide an intermediate frame comprising a plurality of intermediate samples mk(0), . . . , mk(M−1) based on the equation
• mk(n)=zk(n)+zk-1(n+M)
• for n=0, . . . , M−1;
• and
• a lifter configured to provide an added frame comprising a plurality of added samples outk(0), . . . , outk(M−1) based on the equation
• outk(n)=mk(n)+l(n−M/2)·mk-1(M−1−n)
• for n=M/2, . . . , M−1
• and
• outk(n)=mk(n)+l(M−1−n)·outk-1(M−1−n)
• for n=0, . . . , M/2−1,
• wherein l(0), . . . , l(M−1) are real-valued lifting coefficients, wherein inverse type-IV discrete cosine transform frequency/time converter, the windower, the overlap/adder, or the lifter comprises a hardware implementation.

Encoder comprising:

• an analysis filterbank for filtering a plurality of time-domain input frames, an input frame comprising a number of ordered input samples,
• comprising:
• a windower configured to generate a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples, wherein the windower is configured to process the plurality of input frames in an overlapping manner using a sample advance value,
• wherein the sample advance value is less than the number of ordered input samples of an input frame divided by 2;
• and
• a time/frequency converter configured to provide an output frame comprising a number of output values, an output frame being a spectral representation of a windowed frame, wherein the windower or the time/frequency converter comprises a hardware implementation.

Audio decoder comprising:

• a synthesis filterbank for filtering a plurality of input frames, each input frame comprising a number of ordered input values,
• comprising:
• a frequency/time converter configured to provide a plurality of output frames, an output frame comprising a number of ordered output samples, an output frame being a time representation of an input frame;
• a windower configured to generate a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples;
• and
• wherein the windower is configured to provide the plurality of windowed samples for a processing in an overlapping manner based on a sample advance value;
• an overlap/adder configured to provide an added frame comprising a start section and a remainder section, an added frame comprising a plurality of added samples by adding at least three windowed samples from at least three windowed frames for an added sample in the remainder section of an added frame and by adding at least two windowed samples from at least two different windowed frames for an added sample in the start section,
• wherein the number of windowed samples added to obtain an added sample in the remainder section is at least one sample higher compared to the number of windowed samples added to obtain an added sample in the start section, or
• wherein the windower is configured to disregard at least the earliest output value according to the order of the ordered output samples or to setting the corresponding windowed samples to a predetermined value or to at least a value in a predetermined range for each windowed frame of the plurality of windowed frames;
• and
• wherein the overlap/adder is configured to provide the added sample in the remainder section of an added frame based on at least three windowed samples from at least three different windowed frames and an added sample in the start section based on at least two windowed samples from at least two different windowed frames, wherein the frequency/time converter, the windower, or the overlap/adder comprises a hardware implementation.

Audio decoder comprising:

• a synthesis filterbank for filtering a plurality of input frames, each input frame comprising M ordered input values yk(0), . . . , yk(M−1), wherein M is a positive integer, and wherein k is an integer indicating a frame index, comprising:
• an inverse type-IV discrete cosine transform frequency/time converter configured to provide a plurality of output frames, an output frame comprising 2M ordered output samples xk(0), . . . , xk(2M−1) based on the input values yk(0), . . . , yk(M−1);
• a windower configured to generate a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples zk(0), . . . , zk(2M−1) based on the equation
• zk(n)=w(n)·xk(n)
• for n=0, . . . , 2M−1,
• wherein n is an integer indicating a sample index, and wherein w(n) is a real-valued window function coefficient corresponding to the sample index n;
• an overlap/adder configured to provide an intermediate frame comprising a plurality of intermediate samples mk(0), . . . , mk(M−1) based on the equation
• mk(n)=zk(n)+zk-1(n+M)
• for n=0, . . . , M−1;
• and
• a lifter configured to provide an added frame comprising a plurality of added samples outk(0), . . . , outk(M−1) based on the equation
• outk(n)=mk(n)+l(n−M/2)·mk-1(M−1−n)
• for n=M/2, . . . , M−1
• and
• outk(n)=mk(n)+l(M−1−n)·outk-1(M−1−n)
• for n=0, . . . , M/2−1,
• wherein l(0), . . . , l(M−1) are real-valued lifting coefficients, wherein inverse type-IV discrete cosine transform frequency/time converter, the windower, the overlap/adder, or the lifter comprises a hardware implementation.

Mixer for mixing a plurality of input frames, each input frame being a spectral representation of a corresponding time-domain frame and each input frame of the plurality of input frames being provided from a different audio source, comprising:

• an entropy decoder configured to entropy decode the plurality of input frames;
• a scaler configured to scale the plurality of entropy decoded input frames in the frequency domain and configured to obtain a plurality of scaled frames in the frequency domain, each scaled frame corresponding to an entropy decoded input frame;
• an adder configured to add up the scaled frames in the frequency domain to generate an added frame in the frequency domain;
• and
• an entropy encoder configured to entropy encoding the added frame to obtain a mixed frame, wherein the entropy decoder, the scaler, the adder, or the entropy encoder comprises a hardware implementation.

Conferencing system comprising:

• a mixer for mixing a plurality of input frames, each input frame being a spectral representation of a corresponding time-domain frame and each input frame of the plurality of input frames being provided from an audio different source,
• comprising:
• an entropy decoder configured to entropy decode the plurality of input frames;
• a scaler configured to scale the plurality of entropy decoded input frames in the frequency domain and configured to obtain a plurality of scaled frames in the frequency domain, each scaled frame corresponding to an entropy decoded input frame;
• an adder configured to add up the scaled frames in the frequency domain to generate an added frame in the frequency domain;
• and
• an entropy encoder configured to entropy encoding the added frame to obtain a mixed frame, wherein the entropy decoder, the scaler, the adder, or the entropy encoder comprises a hardware implementation.

Method for filtering a plurality of time domain input frames of an audio signal, an input frame comprising a number of ordered input samples,

• the method comprising:
• generating, performed by a windower, a plurality of windowed frames by processing the plurality of input frames in an overlapping manner using a sample advance value;
• wherein the sample advance value is less than the number of ordered input samples of an input frame divided by 2;
• and
• providing, performed by a time/frequency converter, a plurality of output frames comprising a number of output values by performing a time/frequency conversion, an output frame being a spectral representation of a windowed frame, wherein the windower or the time/frequency converter comprises a hardware implementation.

Method for filtering a plurality of input frames of an audio signal, each input frame comprising a number of ordered input values,

• the method comprising:
• performing, performed by a frequency/time converter, a frequency/time conversion and providing a plurality of output frames, an output frame comprising a number of ordered output samples, an output frame being a time representation of an input frame;
• generating, performed by a windower, a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples by processing the plurality of output samples for processing the windowed frames in an overlapping manner based on a sample advanced value;
• generating, performed by an overlap/adder, an added frame comprising a start section and a remainder section,
• wherein a added frame comprises an added sample by adding at least three windowed samples from at least three different windowed frames for an added sample in the remainder section of an added frame and an added sample by adding at least two windowed samples from at least two different windowed frames for an added sample in the start section,
• wherein the number of windowed samples added to obtain an added sample is in the remainder section at least one sample higher compared to the number of windowed samples added to obtain an added sample in the start section;
• or
• wherein generating the plurality of windowed frames comprises disregarding at least the earliest output sample according to the order of the ordered output sample or to setting the corresponding windowed sample to a predetermined value to at least a value in a predetermined range for each windowed frame of the plurality of windowed frames;
• and
• wherein providing an added frame comprises providing an added sample by adding at least three windowed samples from at least three different windowed frames for an added sample in the remainder section of an added frame and an added sample by adding at least two windowed samples from at least two different windowed frames for an added sample in the start section, wherein the frequency/time converter, the windower, or the overlap/adder comprises a hardware implementation.

Method for filtering a plurality of input frames of an audio signal, each input frame comprising M ordered input values yk(0), . . . , yk(M−1), wherein M is a positive integer, and wherein k is an integer indicating an index of the input frame,

• the method comprising:
• performing, performed by an inverse type-IV discrete cosine transform/time converter, an inverse type-IV discrete cosine transform and providing a plurality of output frames xk(0), . . . , xk(2M−1) based on the input values yk(0), . . . , yk(M−1);
• generating, performed by a windower, a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples zk(0), . . . , zk(2M−1) based on an equation
• zk(n)=w(n)·xk(n)
• for n=0, . . . , 2M−1,
• wherein n is an integer;
• generating, performed by an overlap/adder, a plurality of intermediate frames, each intermediate frame comprising a plurality of intermediate samples mk(0), . . . , mk(M−1) based on the equation
• mk(n)=zk(n)+zk-1(n+M)
• for n=0, . . . , M−1;
• and
• generating, performed by a lifter, a plurality of added frames comprising a plurality of added samples outk(0), . . . , outk(M) based on an equation
• outk(n)=mk(n)+l(n−M/2)·mk-1(M−1−n)
• for n=M/2, . . . , M−1
• and
• outk(n)=mk(n)+l(M−1−n)·outk-1(M−1−n)
• for n=0, . . . , M/2−1,
• wherein w(0), . . . , w(2M−1) are real-valued window coefficients;
• wherein l(0), . . . , l(M−1) are real-valued lifting coefficients;
• and
• wherein inverse type-IV discrete cosine transform frequency/time converter, the windower, the overlap/adder, or the lifter comprises a hardware implementation.

Non-transitory computer-readable medium having stored thereon a computer program for performing, when running on a computer, a method for filtering a plurality of time domain input frames of an audio signal, an input frame comprising a number of ordered input samples,

• comprising:
• generating a plurality of windowed frames by processing the plurality of input frames in an overlapping manner using a sample advance value;
• wherein the sample advance value is less than the number of ordered input samples of an input frame divided by 2;
• and
• providing a plurality of output frames comprising a number of output values by performing a time/frequency conversion, an output frame being a spectral representation of a windowed frame.

Non-transitory computer-readable medium having stored thereon a computer program for performing, when running on a computer, a method for filtering a plurality of input frames of an audio signal, each input frame comprising a number of ordered input values, comprising:

• performing a frequency/time conversion and providing a plurality of output frames, an output frame comprising a number of ordered output samples, an output frame being a time representation of an input frame;
• generating a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples by processing the plurality of output samples for processing the windowed frames in an overlapping manner based on a sample advanced value;
• generating an added frame comprising a start section and a remainder section,
• wherein a added frame comprises an added sample by adding at least three windowed samples from at least three different windowed frames for an added sample in the remainder section of an added frame and an added sample by adding at least two windowed samples from at least two different windowed frames for an added sample in the start section,
• wherein the number of windowed samples added to obtain an added sample is in the remainder section at least one sample higher compared to the number of windowed samples added to obtain an added sample in the start section;
• or
• wherein generating the plurality of windowed frames comprises disregarding at least the earliest output sample according to the order of the ordered output sample or to setting the corresponding windowed sample to a predetermined value to at least a value in a predetermined range for each windowed frame of the plurality of windowed frames;
• and
• wherein providing an added frame comprises providing an added sample by adding at least three windowed samples from at least three different windowed frames for an added sample in the remainder section of an added frame and an added sample by adding at least two windowed samples from at least two different windowed frames for an added sample in the start section.

Non-transitory computer-readable medium having stored thereon a computer program for performing, when running on a computer, a method for filtering a plurality of input frames of an audio signal, each input frame comprising M ordered input values yk(0), . . . , yk(M−1), wherein M is a positive integer, and wherein k is an integer indicating an index of the input frame,

• comprising:
• performing an inverse type-IV discrete cosine transform and providing a plurality of output frames xk(0), . . . , xk(2M−1) based on the input values yk(0), . . . , yk(M−1);
• generating a plurality of windowed frames, a windowed frame comprising a plurality of windowed samples zk(0), . . . , zk(2M−1) based on an equation
• zk(n)=w(n)·xk(n)
• for n=0, . . . , 2M−1,
• wherein n is an integer;
• generating a plurality of intermediate frames, each intermediate frame comprising a plurality of intermediate samples mk(0), . . . , mk(M−1) based on the equation
• mk(n)=zk(n)+zk-1(n+M)
• for n=0, . . . , M−1;
• and
• generating a plurality of added frames comprising a plurality of added samples outk(0), . . . , outk(M) based on an equation
• outk(n)=mk(n)+l(n−M/2)·mk-1(M−1−n)
• for n=M/2, . . . , M−1
• and
• outk(n)=mk(n)+l(M−1−n)·outk-1(M−1−n)
• for n=0, . . . , M/2−1,
• wherein w(0), . . . , w(2M−1) are real-valued window coefficients;
• and
• wherein l(0), . . . , l(M−1) are real-valued lifting coefficients.

Method for mixing a plurality of input frames, each input frame being a spectral representation of a corresponding time-domain frame and each input frame of the plurality of input frames being provided from a different audio source,

• the method comprising:
• entropy decoding, performed by an entropy decoder, the plurality of input frames;
• scaling, performed by a scaler, the plurality of entropy decoded input frames in the frequency domain and configured to obtain a plurality of scaled frames in the frequency domain, each scaled frame corresponding to an entropy decoded input frame;
• adding-up, performed by an adder, the scaled frames in the frequency domain to generate an added frame in the frequency domain;
• and
• entropy encoding, performed by an entropy encoder, the added frame to obtain a mixed frame, wherein the entropy decoder, the scaler, the adder, or the entropy encoder comprises a hardware implementation.

Non-transitory computer-readable medium having stored thereon a computer program for performing, when running on a computer, a method for mixing a plurality of input frames, each input frame being a spectral representation of a corresponding time-domain frame and each input frame of the plurality of input frames being provided from a different audio source,

• the method comprising:
• entropy decoding the plurality of input frames;
• scaling the plurality of entropy decoded input frames in the frequency domain and configured to obtain a plurality of scaled frames in the frequency domain, each scaled frame corresponding to an entropy decoded input frame;
• adding-up the scaled frames in the frequency domain to generate an added frame in the frequency domain;
• and
• entropy encoding, performed by an entropy encoder, the added frame to obtain a mixed frame.