Apparatus and method for generating a frequency enhanced signal using shaping of the enhancement signal

• US 9,640,189 B2
• Filed: 07/28/2015
• Issued: 05/02/2017
• Est. Priority Date: 01/29/2013
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Disch, Sascha, Geiger, Ralf, Helmrich, Christian, Multrus, Markus, Schmidt, Konstantin
• Primary Examiner(s): AZAD, ABUL K
• Application Number:
  US14/811,285
• Publication Number:
  US 20150332706A1
• Time in Patent Office: 644 Days
• Field of Search: None
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
• CPC Class Codes: G10L 2019/0012 Smoothing of parameters of the decoder interpolation
• CPC Class Codes: G10L 2019/0016 Codebook for LPC parameters
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: G10L 21/0388 Details of processing therefor
• CPC Class Codes: G10L 25/18 the extracted parameters being spectral information of each sub-band

Abstract

An apparatus for generating a frequency enhancement signal has: a calculator for calculating a value describing an energy distribution with respect to frequency in a core signal; and a signal generator for generating an enhancement signal having an enhancement frequency range not included in the core signal, from the core signal, wherein the signal generator is configured for shaping the enhancement signal or the core signal so that a spectral envelope of the enhancement signal or of the core signal depends on the value describing the energy distribution with respect to frequency in the core signal.

Claims

1. An apparatus for generating a frequency enhancement signal, comprising:

a calculator for calculating a value describing an energy distribution with respect to frequency in a core signal;

a signal generator for generating an enhancement signal comprising an enhancement frequency range not comprised in the core signal, from the core signal, and

wherein the signal generator is configured for shaping the enhancement signal or the core signal so that a spectral envelope of the enhancement signal or of the core signal depends on the value describing the energy distribution with respect to frequency in the core signal,

wherein the signal generator is configured to shape the enhancement signal or the core signal so that a first spectral envelope decrease from a first frequency in the enhancement frequency range to a second higher frequency in the enhancement frequency range is acquired for a first value describing a first energy distribution, and so that a second spectral envelope decrease from the first frequency in the enhancement range to the second frequency in the enhancement range is acquired for a second value describing a second energy distribution,

wherein the second frequency is greater than the first frequency,

wherein the second spectral envelope decrease is greater than the first spectral envelope decrease, and

wherein the first value indicates that the core signal comprises an energy concentration at a higher frequency of the core signal compared to the second value.

2. The apparatus of claim 1, further comprising a combiner for combining the enhancement signal and the core signal to acquire the frequency enhancement signal.

3. The apparatus of claim 1,

wherein the calculator is configured to calculate a measure for a spectral centroid of a current frame as the value on the energy distribution,

wherein the signal generator is configured to shape, in accordance with the value for the spectral centroid, so that the spectral centroid at a higher frequency results in a more shallow slope of the spectral envelope than a spectral centroid at a lower frequency.

4. The apparatus in accordance with claim 1, wherein the calculator is configured to calculate the information on the energy distribution using only a frequency portion of the core signal, the frequency portion of the core signal starting at a first frequency and ending at a second frequency higher than the first frequency, wherein the first frequency is higher than a lowest frequency of the core signal or the second frequency is the highest frequency of the core signal.

5. The apparatus in accordance with claim 1,

wherein the value describing an energy distribution is calculated using the following equation:

6. The apparatus in accordance with claim 1,

wherein the signal generator is configured for applying a shaping factor to an input signal, wherein the shaping factor is calculated based on the following equation:

att=p(sp);

wherein att is a value influencing a shaping factor, and p is a polynomial, and sp is the value on the frequency distribution calculated by the calculator.

7. The apparatus in accordance with claim 1, wherein the signal generator is configured for performing the shaping using the following equation:

(t,xover+f)=Qr(t,xover+f)*att^f;

f=1 . . . nBands, or

(t,xover+f)=Qi(t,xover+f)*att^f;

f=1 . . . nBands

wherein is a real part of a shaped subband sample, t is a time index, xover is a crossover frequency, f is a frequency index and att is a constant derived from the value on the spectral distribution, Q_r is a real part of a subband sample before shaping, and Q_i is an imaginary part of a subband sample before shaping.

8. The apparatus in accordance with claim 1,

wherein the core signal comprises a plurality of core signal subbands,

wherein the calculator is configured to calculate individual energies of core signal bands and to calculate the information on the energy distribution using the individual energies.

9. The apparatus in accordance with claim 1,

wherein the core signal comprises a plurality of core signal bands,

wherein the signal generator is configured to copy-up or to mirror one or a plurality of core signal bands to acquire a plurality of enhancement signal bands forming the enhancement frequency range.

10. The apparatus in accordance with claim 1,

wherein the calculator is configured to calculate the value based on the following equation:

11. The apparatus in accordance with claim 1,

wherein the signal generator is configured to perform, subsequent to or concurrent to the shaping of the enhancement signal or the core signal, a temporal smoothing operation, the temporal smoothing operation comprising finding a decision about a smoothing intensity and applying the smoothing operation to the enhancement frequency range or the core signal based on the decision.

12. The apparatus in accordance with claim 1,

wherein the signal generator is configured to apply a band-wise energy limitation subsequent to the shaping or the temporal smoothing or concurrent to the shaping or the temporal smoothing.

13. A method of generating a frequency enhancement signal, comprising:

calculating a value describing an energy distribution with respect to frequency in a core signal;

generating an enhancement signal comprising an enhancement frequency range not comprised in the core signal, from the core signal, and

wherein the generating comprises shaping the enhancement signal or the core signal so that a spectral envelope of the enhancement signal or of the core signal depends on the value describing the energy distribution with respect to frequency in the core signal,

wherein the generating comprises shaping the enhancement signal or the core signal so that a first spectral envelope decrease from a first frequency in the enhancement frequency range to a second higher frequency in the enhancement frequency range is acquired for a first value describing a first energy distribution, and so that a second spectral envelope decrease from the first frequency in the enhancement range to the second frequency in the enhancement range is acquired for a second value describing a second energy distribution,

wherein the second frequency is greater than the first frequency,

wherein the second spectral envelope decrease is greater than the first spectral envelope decrease, and

wherein the first value indicates that the core signal comprises an energy concentration at a higher frequency of the core signal compared to the second value.

14. A system for processing audio signals, comprising:

an encoder for generating an encoded core signal; and

an apparatus for generating a frequency enhancement signal, the apparatus comprising;

a calculator for calculating a value describing an energy distribution with respect to frequency in a core signal;

a signal generator for generating an enhancement signal comprising an enhancement frequency range not comprised in the core signal, from the core signal, and

wherein the signal generator is configured for shaping the enhancement signal or the core signal so that a spectral envelope of the enhancement signal or of the core signal depends on the value describing the energy distribution with respect to frequency in the core signal,

wherein the signal generator is configured to shape the enhancement signal or the core signal so that a first spectral envelope decrease from a first frequency in the enhancement frequency range to a second higher frequency in the enhancement frequency range is acquired for a first value describing a first energy distribution, and so that a second spectral envelope decrease from the first frequency in the enhancement range to the second frequency in the enhancement range is acquired for a second value describing a second energy distribution,

wherein the second frequency is greater than the first frequency,

wherein the second spectral envelope decrease is greater than the first spectral envelope decrease, and

wherein the first value indicates that the core signal comprises an energy concentration at a higher frequency of the core signal compared to the second value.

15. A method for processing audio signals, comprising:

generating an encoded core signal; and

generating a frequency enhancement signal, the generating comprising;

calculating a value describing an energy distribution with respect to frequency in a core signal;

generating an enhancement signal comprising an enhancement frequency range not comprised in the core signal, from the core signal, and

wherein the generating comprises shaping the enhancement signal or the core signal so that a spectral envelope of the enhancement signal or of the core signal depends on the value describing the energy distribution with respect to frequency in the core signal,

wherein the generating comprises shaping the enhancement signal or the core signal so that a first spectral envelope decrease from a first frequency in the enhancement frequency range to a second higher frequency in the enhancement frequency range is acquired for a first value describing a first energy distribution, and so that a second spectral envelope decrease from the first frequency in the enhancement range to the second frequency in the enhancement range is acquired for a second value describing a second energy distribution,

wherein the second frequency is greater than the first frequency,

wherein the second spectral envelope decrease is greater than the first spectral envelope decrease, and

wherein the first value indicates that the core signal comprises an energy concentration at a higher frequency of the core signal compared to the second value.

16. A non-transitory storage medium having stored thereon a computer program for performing, when running on a computer or a processor, a method of generating a frequency enhancement signal, the method comprising:

calculating a value describing an energy distribution with respect to frequency in a core signal;

generating an enhancement signal comprising an enhancement frequency range not comprised in the core signal, from the core signal, and

wherein the generating comprises shaping the enhancement signal or the core signal so that a spectral envelope of the enhancement signal or of the core signal depends on the value describing the energy distribution with respect to frequency in the core signal,

wherein the generating comprises shaping the enhancement signal or the core signal so that a first spectral envelope decrease from a first frequency in the enhancement frequency range to a second higher frequency in the enhancement frequency range is acquired for a first value describing a first energy distribution, and so that a second spectral envelope decrease from the first frequency in the enhancement range to the second frequency in the enhancement range is acquired for a second value describing a second energy distribution,

wherein the second frequency is greater than the first frequency,

wherein the second spectral envelope decrease is greater than the first spectral envelope decrease, and

wherein the first value indicates that the core signal comprises an energy concentration at a higher frequency of the core signal compared to the second value.

17. A non-transitory storage medium having stored thereon a computer program for performing, when running on a computer or a processor, a method for processing audio signals, the method comprising:

generating an encoded core signal; and

generating a frequency enhancement signal, the generating comprising;

calculating a value describing an energy distribution with respect to frequency in a core signal;

generating an enhancement signal comprising an enhancement frequency range not comprised in the core signal, from the core signal, and

wherein the generating comprises shaping the enhancement signal or the core signal so that a spectral envelope of the enhancement signal or of the core signal depends on the value describing the energy distribution with respect to frequency in the core signal,

wherein the generating comprises shaping the enhancement signal or the core signal so that a first spectral envelope decrease from a first frequency in the enhancement frequency range to a second higher frequency in the enhancement frequency range is acquired for a first value describing a first energy distribution, and so that a second spectral envelope decrease from the first frequency in the enhancement range to the second frequency in the enhancement range is acquired for a second value describing a second energy distribution,

wherein the second frequency is greater than the first frequency,

wherein the second spectral envelope decrease is greater than the first spectral envelope decrease, and

wherein the first value indicates that the core signal comprises an energy concentration at a higher frequency of the core signal compared to the second value.