Apparatus and method for MDCT M/S stereo with global ILD with improved mid/side decision

A system for encoding four channels of an audio input signal comprising four or more channels to acquire an encoded audio signal, the system comprising:

• a first apparatus for encoding a first channel and a second channel of the four or more channels of the audio input signal to acquire a first channel and a second channel of the encoded audio signal, and
• a second apparatus,
• wherein the first apparatus is configured for encoding a first channel and a second channel of the audio input signal,
• wherein the first apparatus comprises a normalizer configured to determine a first channel and a second channel of a normalized audio signal by modifying, depending on a normalization value, at least one of the first channel and the second channel of the audio input signal,
• wherein the first apparatus comprises an encoding unit being configured to generate a processed audio signal comprising a first channel and a second channel, such that one or more spectral bands of the first channel of the processed audio signal are one or more spectral bands of the first channel of the normalized audio signal, such that one or more spectral bands of the second channel of the processed audio signal are one or more spectral bands of the second channel of the normalized audio signal, such that at least one spectral band of the first channel of the processed audio signal is a spectral band of a mid signal obtained by processing a spectral band of the first channel of the normalized audio signal and a spectral band of the second channel of the normalized audio signal, and such that at least one spectral band of the second channel of the processed audio signal is a spectral band of a side signal obtained by processing a spectral band of the first channel of the normalized audio signal and depending on a spectral band of the second channel of the normalized audio signal, wherein the encoding unit is configured to encode the processed audio signal to acquire the encoded audio signal,
• wherein the second apparatus is configured for encoding a third channel and a fourth channel of the four or more channels of the audio input signal to acquire a third channel and a fourth channel of the encoded audio signal.

An apparatus for decoding an encoded audio signal comprising a first channel and a second channel to acquire a first channel and a second channel of a decoded audio signal comprising two or more channels,

• wherein the apparatus comprises a decoding unit configured to determine for each spectral band of a plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using dual-mono encoding or using mid-side encoding,
• wherein the decoding unit is configured to generate a spectral band of a first channel of an intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using
• the spectral band of the second channel of the encoded audio signal, and to generate a spectral band of a second channel of the intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using the spectral band of the second channel of the encoded audio signal, if the mid-side encoding was used, and
• wherein the apparatus comprises a de-normalizer configured to modify, depending on a de-normalization value, at least one of the first channel and the second channel of the intermediate audio signal to acquire the first channel and the second channel of the decoded audio signal,
• wherein the decoding unit is configured to determine for each spectral band of the plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using the dual-mono encoding or using the mid-side encoding,
• wherein the decoding unit is configured to acquire the spectral band of the second channel of the encoded audio signal by reconstructing the spectral band of the second channel,
• wherein, if the mid-side encoding was used, the spectral band of the first channel of the encoded audio signal is a spectral band of a mid signal, and the spectral band of the second channel of the encoded audio signal is a spectral band of a side signal,
• wherein, if the mid-side encoding was used, the decoding unit is configured to reconstruct the spectral band of the side signal depending on a correction factor for the spectral band of the side signal and depending on a spectral band of a previous mid signal, which corresponds to the spectral band of the mid signal, wherein the previous mid signal precedes the mid signal in time.

A system for decoding an encoded audio signal comprising four or more channels to acquire four channels of a decoded audio signal comprising four or more channels,

• wherein the system comprises a first and second apparatus for decoding a first channel and a second channel of the four or more channels of the encoded audio signal to acquire a first channel and a second channel of the decoded audio signal
• wherein the system comprises a second apparatus,
• wherein the first apparatus comprises a decoding unit configured to determine for each spectral band of a plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using dual-mono encoding or using mid-side encoding,
• wherein the decoding unit of the first apparatus is configured to generate a spectral band of a first channel of an intermediate audio signal
• based on the spectral band of the first channel of the encoded audio signal and based on the spectral band of the second channel of the encoded audio signal, and to generate a spectral band of a second channel of the intermediate audio signal based on the spectral band of the first channel of the encoded audio signal and based on the spectral band of the second channel of the encoded audio signal, if the mid-side encoding was used, and
• wherein the first apparatus comprises a de-normalizer configured to modify, depending on a de-normalization value, at least one of the first channel and the second channel of the intermediate audio signal to acquire the first channel and the second channel of the decoded audio signal,
• wherein the decoding unit is configured to determine for each spectral band of the plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using the dual-mono encoding or using the mid-side encoding,
• wherein the decoding unit of the first apparatus is configured to acquire the spectral band of the second channel of the encoded audio signal by reconstructing the spectral band of the second channel,
• wherein, if the mid-side encoding was used, the spectral band of the first channel of the encoded audio signal is a spectral band of a mid signal, and the spectral band of the second channel of the encoded audio signal is a spectral band of a side signal,
• wherein, if the mid-side encoding was used, the decoding unit of the first apparatus is configured to reconstruct the spectral band of the side signal depending on a correction factor for the spectral band of the side signal and depending on a spectral band of a previous mid signal, which corresponds to the spectral band of the mid signal, wherein the previous mid signal precedes the mid signal in time, and
• wherein the second apparatus is configured for decoding a third channel and a fourth channel of the four or more channels of the encoded audio signal to acquire a third channel and a fourth channel of the decoded audio signal.

A system for generating an encoded audio signal from an audio input signal, comprising:

• an apparatus for encoding a first channel and a second channel of the audio input signal comprising two or more channels to acquire the encoded audio signal, the apparatus being configured to generate the encoded audio signal from the audio input signal and comprising:
• a normalizer configured to determine a first channel and a second channel of a normalized audio signal by modifying, depending on a normalization value, at least one of the first channel and the second channel of the audio input signal,
• an encoding unit being configured to generate a processed audio signal comprising a first channel and a second channel, such that one or more spectral bands of the first channel of the processed audio signal are one or more spectral bands of the first channel of the normalized audio signal, such that one or more spectral bands of the second channel of the processed audio signal are one or more spectral bands of the second channel of the normalized audio signal, such that at least one spectral band of the first channel of the processed audio signal is a spectral band of a mid signal obtained by processing a spectral band of the first channel of the normalized audio signal and a spectral band of the second channel of the normalized audio signal, and such that at least one spectral band of the second channel of the processed audio signal is a spectral band of a side signal obtained by processing a spectral band of the first channel of the normalized audio signal and a spectral band of the second channel of the normalized audio signal, wherein the encoding unit is configured to encode the processed audio signal to acquire the encoded audio signal.

A system for generating a decoded audio signal from an encoded audio signal, comprising:

• an apparatus for decoding the encoded audio signal comprising a first channel and a second channel to acquire a first channel and a second channel of the decoded audio signal comprising two or more channels,
• the apparatus being configured to generate the decoded audio signal from the encoded audio signal and comprising a decoding unit configured to determine for each spectral band of a plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using dual-mono encoding or using mid-side encoding,
• wherein the decoding unit is configured to generate a spectral band of a first channel of an intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using the
• spectral band of the second channel of the encoded audio signal, and to generate a spectral band of a second channel of the intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using the spectral band of the second channel of the encoded audio signal, if the mid-side encoding was used, and
• wherein the apparatus comprises a de-normalizer configured to modify, depending on a de-normalization value, at least one of the first channel and the second channel of the intermediate audio signal to acquire the first channel and the second channel of the decoded audio signal,
• wherein the decoding unit is configured to determine for each spectral band of the plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using the dual-mono encoding or using the mid-side encoding,
• wherein the decoding unit is configured to acquire the spectral band of the second channel of the encoded audio signal by reconstructing the spectral band of the second channel,
• wherein, if the mid-side encoding was used, the spectral band of the first channel of the encoded audio signal is a spectral band of a mid signal, and the spectral band of the second channel of the encoded audio signal is spectral band of a side signal,
• wherein, if the mid-side encoding was used, the decoding unit is configured to reconstruct the spectral band of the side signal depending on a correction factor for the spectral band of the side signal and depending on a spectral band of a previous mid signal, which corresponds to the spectral band of the mid signal, wherein the previous mid signal precedes the mid signal in time.

A system for generating a decoded audio signal from an encoded audio signal, comprising:

• a system for decoding an encoded audio signal comprising four or more channels to acquire four channels of a decoded audio signal comprising four or more channels, wherein the system for decoding is configured to generate the decoded audio signal from the encoded audio signal,
• wherein the system comprises a first apparatus for decoding the encoded audio signal to acquire a first channel and a second channel of the decoded audio signal,
• wherein the system comprises a second apparatus,
• wherein the first apparatus comprises a decoding unit configured to determine for each spectral band of a plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using dual-mono encoding or using mid-side encoding,
• wherein the decoding unit is configured to generate a spectral band of a first channel of an intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using the
• spectral band of the second channel of the encoded audio signal, and to generate a spectral band of the second channel of a intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using the spectral band of the second channel of the encoded audio signal, if the mid-side encoding was used, and
• wherein the first apparatus comprises a de-normalizer configured to modify, depending on a de-normalization value, at least one of the first channel and the second channel of the intermediate audio signal to acquire the first channel and the second channel of the decoded audio signal,
• wherein the decoding unit is configured to determine for each spectral band of the plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using the dual-mono encoding or using the mid-side encoding,
• wherein the decoding unit is configured to acquire the spectral band of the second channel of the encoded audio signal by reconstructing the spectral band of the second channel,
• wherein, if the mid-side encoding was used, the spectral band of the first channel of the encoded audio signal is a spectral band of a mid signal, and the spectral band of the second channel of the encoded audio signal is spectral band of a side signal, wherein, if the mid-side encoding was used, the decoding unit is configured to reconstruct the spectral band of the side signal depending on a correction factor for the spectral band of the side signal and depending on a spectral band of a previous mid signal, which corresponds to the spectral band of the mid signal, wherein the previous mid signal precedes the mid signal in time,
• wherein the second apparatus is configured for decoding a third channel and a fourth channel of the four or more channels of the encoded audio signal to acquire a third channel and a fourth channel of the decoded audio signal.

A method for encoding a first channel and a second channel of an audio input signal comprising two or more channels to acquire an encoded audio signal, the method comprising:

• determining a first channel and a second channel of a normalized audio signal by modifying, depending on a normalization value, at least one of the first channel and the second channel of the audio input signal,
• generating a processed audio signal comprising a first channel and a second channel, such that one or more spectral bands of the first channel of the processed audio signal are one or more spectral bands of the first channel of the normalized audio signal, such that one or more spectral bands of the second channel of the processed audio signal are one or more spectral bands of the second channel of the normalized audio signal, such that at least one spectral band of the first channel of the processed audio signal is a spectral band of a mid signal obtained by processing a spectral band of the first channel of the normalized audio signal and a spectral band of the second channel of the normalized audio signal, and such that at least one spectral band of the second channel of the processed audio signal is a spectral band of a side signal obtained by processing a spectral band of the first channel of the normalized audio signal and a spectral band of the second channel of the normalized audio signal, and encoding the processed audio signal to acquire the encoded audio signal.

A method for decoding an encoded audio signal comprising a first channel and a second channel to acquire a first channel and a second channel of a decoded audio signal comprising two or more channels, wherein the method comprises:

• determining for each spectral band of a plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using dual-mono encoding or using mid-side encoding,
• generating a spectral band of a first channel of an intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using the spectral band of the second channel of the encoded audio signal, and generating a spectral band of a second channel of the intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using the spectral band of the second channel of the encoded audio signal, when the mid-side encoding is used, and
• modifying, depending on a de-normalization value, at least one of the first channel and the second channel of the intermediate audio signal to acquire the first channel and the second channel of the decoded audio signal,
• wherein the method further comprises:
• determining for each spectral band of the plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using the dual-mono encoding or using the mid-side encoding,
• acquiring the spectral band of the second channel of the encoded audio signal by reconstructing the spectral band of the second channel,
• using the mid-side encoding, the spectral band of the first channel of the encoded audio signal is a spectral band of a mid signal, and the spectral band of the second channel of the encoded audio signal is spectral band of a side signal, and
• when using the mid-side encoding, the method comprises reconstructing the spectral band of the side signal depending on a correction factor for the spectral band of the side signal and depending on a spectral band of a previous mid signal, which corresponds to the spectral band of the mid signal, wherein the previous mid signal precedes the mid signal in time.

A non-transitory digital storage medium having a computer program stored thereon to perform

• a method for encoding a first channel and a second channel of an audio input signal comprising two or more channels to acquire an encoded audio signal, the method comprising:
• determining a first channel and a second channel of a normalized audio signal by modifying, depending on a normalization value, at least one of the first channel and the second channel of the audio input signal,
• generating a processed audio signal comprising a first channel and a second channel, such that one or more spectral bands of the first channel of the processed audio signal are one or more spectral bands of the first channel of the normalized audio signal, such that one or more spectral bands of the second channel of the processed audio signal are one or more spectral bands of the second channel of the normalized audio signal, such that at least one spectral band of the first channel of the processed audio signal is a spectral band of a mid signal
• obtained by processing a spectral band of the first channel of the normalized audio signal and
• a spectral band of the second channel of the normalized audio signal, and such that at least one spectral band of the second channel of the processed audio signal is a spectral band of a side signal obtained by processing a spectral band of the first channel of the normalized audio signal and a spectral band of the second channel of the normalized audio signal, and encoding the processed audio signal to acquire the encoded audio signal,
• when the computer program is run by a computer or signal processor.

A non-transitory digital storage medium having a computer program stored thereon to perform the method for decoding an encoded audio signal comprising a first channel and a second channel to acquire a first channel and a second channel of a decoded audio signal comprising two or more channels, the method comprising:

• determining for each spectral band of a plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using dual-mono encoding or using mid-side encoding,
• generating a spectral band of a first channel of an intermediate audio signal using the spectral band of the first channel of the encoded audio signal and using the spectral band of the second channel of the encoded audio signal, and generating a spectral band of a second channel of the intermediate audio signal
• using the spectral band of the first channel of the encoded audio signal and using the spectral band of the second channel of the encoded audio signal, when the mid-side encoding is used, and
• modifying, depending on a de-normalization value, at least one of the first channel and the second channel of the intermediate audio signal to acquire the first channel and the second channel of the decoded audio signal,
• wherein the method further comprises:
• determining for each spectral band of the plurality of spectral bands, whether the spectral band of the first channel of the encoded audio signal and the spectral band of the second channel of the encoded audio signal was encoded using the dual-mono encoding or using the mid-side encoding,
• acquiring the spectral band of the second channel of the encoded audio signal by reconstructing the spectral band of the second channel,
• wherein, if the mid-side encoding was used, the spectral band of the first channel of the encoded audio signal is a spectral band of a mid signal, and the spectral band of the second channel of the encoded audio signal is spectral band of a side signal,
• wherein, if the mid-side encoding was used, the method comprises reconstructing the spectral band of the side signal depending on a correction factor for the spectral band of the side signal and depending on a spectral band of a previous mid signal, which corresponds to the spectral band of the mid signal, wherein the previous mid signal precedes the mid signal in time,
• when the computer program is run by a computer or signal processor.