Phase coherence control for harmonic signals in perceptual audio codecs

1. An apparatus for audio decoding for decoding an encoded audio signal to acquire a modified audio signal, comprising:

a decoding unit; for decoding the encoded audio signal to acquire a decoded audio signal, and

a phase adjustment unit, wherein the phase adjustment unit is configured to receive the decoded audio signal,

wherein the phase adjustment unit is configured to receive control information indicating a vertical phase coherence of the encoded audio signal, and

wherein, to acquire the modified audio signal being adjusted in phase, the phase adjustment unit is adapted to modify the decoded audio signal using the vertical phase coherence of the control information,

wherein the audio decoder is implemented using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer.

2. The apparatus according to claim 1 ,

wherein the phase adjustment unit is configured to adjust the decoded audio signal when the control information indicates that the phase adjustment is activated, and

wherein the phase adjustment unit is configured not to adjust the decoded audio signal when the control information indicates that phase adjustment is deactivated.

3. The apparatus according to claim 1 ,

wherein the phase adjustment unit is configured to receive the control information, wherein the control information comprises a strength value indicating a strength of a phase adjustment, and

wherein the phase adjustment unit is configured to adjust the decoded audio signal based on the strength value.

4. The apparatus according to claim 1 ,

wherein the audio decoder further comprises an analysis filter bank for decomposing the decoded audio signal into a plurality of subband signals of a plurality of subbands,

wherein the phase adjustment unit is configured to determine a plurality of first phase values of the plurality of subband signals, and

wherein the phase adjustment unit is adapted to adjust the encoded audio signal by modifying at least some of the plurality of the first phase values to acquire second phase values of the phase-adjusted audio signal.

5. The apparatus according to claim 4 ,

wherein the phase adjustment unit is configured to adjust at least some of the phase values by applying the formulae:

px ′( f )= px ( f )− dp ( f ), and

dp ( f )=α*( p 0( f )+const),

wherein f is a frequency indicating the one of the subbands which comprises the frequency f as a center frequency,

wherein px(f) is one of the first phase values of one of the subband signals of one of the subbands comprising the frequency f as the center frequency,

wherein px′(f) is one of the second phase values of one of the subband signals of one of the subbands comprising the frequency f as the center frequency,

wherein const is a first angle in the range −π<const <π,

wherein α is a real number in the range 0<α<1; and

wherein p 0 (f) is a second angle in the range −π<p 0 (f) <π, wherein the second angle p 0 (f) is assigned to the one of the subbands comprising the frequency f as the center frequency.

6. The apparatus according to claim 4 ,

wherein the phase adjustment unit is configured to adjust at least some of the phase values by multiplying at least some of the plurality of subband signals by an exponential phase term,

wherein the exponential phase term is defined by the formula e −jdp(f) ,

wherein the plurality of subband signals are complex subband signals, and

wherein j is the unit imaginary number.

7. The apparatus according to claim 1 ,

wherein the audio decoder further comprises a synthesis filter bank,

wherein the phase-adjusted audio signal is a phase-adjusted spectral-domain audio signal being represented in a spectral domain, and

wherein the synthesis filter bank is configured to transform the phase adjusted spectral-domain audio signal from the spectral domain to a time domain to acquire a phase-adjusted time-domain audio signal.

8. An apparatus for audio encoding for encoding control information based on an audio input signal, comprising:

a transformation unit for transforming the audio input signal from a time-domain to a spectral domain to acquire a transformed audio signal comprising a plurality of subband signals being assigned to a plurality of subbands,

a control information generator for generating the control information which indicates a vertical phase coherence of the transformed audio signal, and

an encoding unit for encoding the transformed audio signal and the control information to obtain encoded audio information that is decodable,

wherein the audio encoder is implemented using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer.

9. The apparatus according to claim 8 ,

wherein the transformation unit comprises a cochlear filter bank for transforming the audio input signal from the time-domain to the spectral domain to acquire the transformed audio signal comprising the plurality of subband signals.

10. The apparatus according to claim 8 ,

wherein the control information generator is configured to determine a subband envelope for each of the plurality of subband signals to acquire a plurality of subband signal envelopes,

wherein the control information generator is configured to generate a combined envelope based on the plurality of subband signal envelopes, and

wherein the control information generator is configured to generate the control information based on the combined envelope.

11. The apparatus according to claim 10 ,

wherein the control information generator is configured to generate a characterizing number based on the combined envelope, and

wherein the control information generator is configured to generate the control information such that the control information indicates that phase adjustment is activated when the characterizing number is greater than a threshold value, and

wherein the control information generator is configured to generate the control information such that the control information indicates that the phase adjustment is deactivated when the characterizing number is smaller than or equal to the threshold value.

12. The apparatus according to claim 10 ,

wherein the control information generator is configured to generate the control information by calculating a ratio of a geometric mean of the combined envelope to an arithmetic mean of the combined envelope.

13. The apparatus according to claim 8 ,

wherein the control information generator is configured to generate the control information such that the control information comprises a strength value indicating a degree of vertical phase coherence of the subband signals.

14. An apparatus for modifying a first audio signal to acquire a second audio signal, comprising:

a control information generator for generating control information such that the control information indicates a vertical phase coherence of the first audio signal, and

a phase adjustment unit for modifying the first audio signal to acquire the second audio signal,

wherein the phase adjustment unit is adapted to modify the first audio signal using the vertical phase coherence of the control information,

wherein the apparatus is implemented using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer.

15. A system comprising,

an apparatus for audio encoding for encoding control information based on an audio input signal, comprising: a transformation unit for transforming the audio input signal from a time-domain to a spectral domain to acquire a transformed audio signal comprising a plurality of subband signals being assigned to a plurality of subbands, a control information generator for generating the control information such that the control information indicates a vertical phase coherence of the transformed audio signal, and an encoding unit for encoding the transformed audio signal and the control information, and

at least one apparatus for audio decoding according to claim 1 ,

wherein the apparatus for audio encoding is configured to transform an audio input signal to acquire a transformed audio signal,

wherein the apparatus for audio encoding is configured to encode the transformed audio signal to acquire an encoded audio signal,

wherein the apparatus for audio encoding is configured to encode control information indicating a vertical phase coherence of the transformed audio signal,

wherein the apparatus for audio encoding is arranged to feed the encoded audio signal and the control information into the at least one audio decoder,

wherein the at least one apparatus for audio decoding is configured to decode the encoded audio signal to acquire a decoded audio signal, and

wherein the at least one apparatus for audio decoding is configured to adjust the decoded audio signal based on the encoded control information to acquire a phase-adjusted audio signal,

wherein at least one of the apparatus for audio encoding and the at least one apparatus for audio decoding is implemented using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer.

16. A method for decoding an encoded audio signal to acquire a modified audio signal, comprising:

decoding the encoded audio signal to acquire a decoded audio signal, and

receiving the decoded audio signal,

receiving control information indicating a vertical phase coherence of the encoded audio signal, and

modifying, to acquire the modified audio signal being adjusted in phase, the decoded audio signal using the vertical phase coherence of the control information,

wherein the method is performed using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer.

17. A method for encoding control information based on an audio input signal, comprising:

transforming the audio input signal from a time-domain to a spectral domain to acquire a transformed audio signal comprising a plurality of subband signals being assigned to a plurality of subbands, generating the control information indicating a vertical phase coherence of the transformed audio signal, and

encoding the transformed audio signal and the control information to obtain encoded audio information that is decodable,

wherein the method is performed using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer.

18. A method for processing a first audio signal to acquire a second audio signal, comprising:

generating control information indicating a vertical phase coherence of the first audio signal, and

modifying the first audio signal based on the control information to acquire the second audio signal,

wherein modifying the first audio signal is conducted using the vertical phase coherence of the control information,

wherein the method is performed using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer.

19. A non-transitory computer-readable medium comprising a computer program for implementing the method according to claim 16 when being executed by a computer or signal processor.

20. A non-transitory computer-readable medium comprising a computer program for implementing the method according to claim 17 when being executed by a computer or signal processor.

21. A non-transitory computer-readable medium comprising a computer program for implementing the method according to claim 18 when being executed by a computer or signal processor.

22. An apparatus for audio decoding for decoding an encoded audio signal to acquire a modified audio signal, comprising:

a decoding unit; for decoding the encoded audio signal to acquire a decoded audio signal, and

a phase adjustment unit, wherein the phase adjustment unit is configured to receive the decoded audio signal,

wherein the phase adjustment unit is configured to receive control information indicating a vertical phase coherence of the encoded audio signal, and

wherein, to acquire the modified audio signal being adjusted in phase, the phase adjustment unit is adapted to modify the decoded audio signal using the vertical phase coherence of the control information,

wherein the audio decoder is implemented using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer,

wherein the control information depends on a combined envelope, wherein the combined envelope depends a subband envelope of each of the plurality of subband signals, and wherein the phase adjustment unit is configured to determine the subband envelope for each of a plurality of subbands of the decoded audio signal depending on the control information to acquire the modified audio signal.

23. An apparatus for audio encoding for encoding control information based on an audio input signal, comprising:

a transformation unit for transforming the audio input signal from a time-domain to a spectral domain to acquire a transformed audio signal comprising a plurality of subband signals being assigned to a plurality of subbands,

a control information generator for generating the control information which indicates a vertical phase coherence of the transformed audio signal, and

an encoding unit for encoding the transformed audio signal and the control information to obtain encoded audio information that is decodable,

wherein the audio encoder is implemented using a hardware apparatus or using a computer or using a combination of a hardware apparatus and a computer,

wherein the control information generator is configured to generate the control information depending on a combined envelope, wherein the combined envelope depends a subband envelope of each of the plurality of subband signals.